MX Tuner

Technical Questions? - Ask

Jul. 01, 2001 By Mark Klein
Mark Klein is ready to answer your technical questions! Mark has extensive experience race tuning off-road motorcycles for local and national races. If you check back through our 1998/99 archives you will see a series called "Dirtbikes 101." Mark brings his expertise to fielding your maintenance and tuning questions.

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Oil To Burn
Transmission oil has to be added after each ride 1-4 ounces depending on how long and how hard it is ridden is this normal? No external leaks where could oil be going?

Please help, 45-year-old new rider.

Could be your right side crankshaft seal. It can suck it into the crankcase area and burn it. This is the most likely place for it to consume oil without any external leaks. Most bikes can have this seal replaced by removing the right side cover; clutch and primary drive gear to expose the seal. Some bikes (some Kawasakis come to mind right off hand) require splitting the cases for this repair. This could get expensive by the time you replace all the seals, gaskets and bearings even if everything else inside the motor is in good condition.

Hopefully, you'll be able to gain access to the seal without splitting the cases. With it burning that much oil, it would probably be a good idea to repack your silencer once you get the seal replaced. The excess oil can saturate the packing.

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Free YZ
Hi Mark. I have a problem with a 99 YZ 125. It runs fine when the engine is not hot, what I mean is after you warm it up and then clean it out it runs great. After you get it out on the track and run about 1-2 laps it starts to cut out on the bottom and top. It sounds like it is fat on the bottom, and on the top it sputters like the float height is wrong. I just got the bike and get this... for free... The previous owner's dad wanted it out of the garage and didn't want to dump any more money into it. The bike has a pro circuit pipe and silencer and a RAD valve. The jetting started at a 350 main, now is 380. The pilot is 45. Plug looks good-dark brown. The compression is 120lbs. The air filter is clean; all electric connections are clean and tight. I am thinking I have a coil acting up after it gets warm. Have you heard of any problems like this? I hope you can help.

Thanks. Russ

I can't imagine you'd need a 380 main jet or the 45 pilot. It seems you're headed in the right direction looking at electrical components. Be sure to unbolt the ignition coil to guarantee the mounting tabs are corrosion and rust free. Most of the time I run into an electrical component causing erratic jetting, it is the CDI box. But any one of them can give some strange symptoms. Your best bet is finding someone with another '99 YZ 125 and start swapping parts. I'd definitely go back to stock jetting during your diagnosing and then fine tune the jetting once you get to the root of the problem.

One other obscure thing to watch for is the float level of each side of the float. I've seen brand-new bikes (a YZ 125 in particular) that have the float tang bent so one side is correct and the other is way off. This particular bike ran fine in left turns and ran terrible in right turns. But depending how far off it is, you could have something similar.

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1990 CR 125
I bought this bike a few weeks ago. When I was out riding I noticed that first was really choppy, grabby, it felt like the chain was to loose and engaging really hard. It got worst until it didn't engage at all. I drained the oil it was gray in color with small specks of steel, not allot just some. So on disassembly we notice a water pump bearing was broke. We couldn't find one of the bearings.

A week before I was riding and one of the water pump hoses fell off, I don't know for how long. Maybe a lap, I stalled out on my account and noticed it when I looked down. Maybe because I ran it out of water?

The transmission forks where good but one, right one it is bent slightly with wear heavy to the to the one side, is this the 1st gear problem? I also noticed that the transmission shaft with the first 1st gear, is one unit and one of the teeth has a chip missing from it. It would still mesh ok but I am replacing anyways.

Problem three: The piston has been hitting the head. I noticed a ring around the top of the piston. I looked at the head and see where it has been hitting about a .03" ring on the one rad. it looks like it has definitely been milled. What is the squish for a 1990 CR 125? What should I do about this? Otherwise it is a good bike, starts on the first kick most of the time. A lot of carbon deposits in the exhaust and HPP more like black goop.

Hope u can help me.


The choppy, grabby feel sounds like the clutch acting up. The water-contaminated oil certainly won't help the clutch work correctly. Check the thickness of the fiber plates. Check the metal plates for warpage. You can do this by laying them on a piece of glass and using a feeler gauge. Check the clutch basket and hub for notches where the plates ride against them. If the metal plates are made of aluminum, I'd highly recommend replacing them with steel plates. I don't remember what that bike came with from the factory. The aluminum plates are slightly better for performance but are much worse for durability and clutch feel.

The shift fork with any signs of wear must be replaced. Even if it isn't bent, the wear is enough to condemn it. The $35 or so it'll cost is a drop in the bucket if you have to pull it apart again.

Has the piston actually been hitting the head or is the markings you're seeing signs of detonation? Either way, I'd recommend having the head remachined by someone who knows what they are doing. Eric Gorr would be an excellent choice for this work. Don't take this lightly. If this isn't done right, you can have a bike that runs fine? until the piston develops a new hole in the top of it. Eric can be reached at Tell him I sent you.

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175 PE Suzuki 1981
When I try to kick start it, the starting lever only goes down half way. Thus not starting the bike. I have had any other problems. I haven't tried anything because I don't know what to do.

Thanks - Patrick

You'll need to remove the right side cover to inspect the kickstart mechanism. You may also have to remove the clutch, depending on what you discover once you get in there. If it were anything else, you'd have a different symptom. A good visual inspection should reveal your problem.

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2000 Yamaha YZ80
Greetings! I recently purchased a used 2000 Yamaha YZ80 for my son. We are both new to dirt bikes. It has been well ridden, raced, but seemed to be in good condition for the price. I was told that it has been about 6 months since a top end was done and that it was probably getting close to needing one. The bike seems to run well but I have a couple of concerns.

1. It has a pinging or tinging sound during idle and through the power range; however it is less noticeable when revving, sounds like it is coming from the engine.

2. It is dripping oil or goo out the tail pipe. The spark plug according to the book is running rich. It is wet and black-coated.

We bought the bike at an elevation of 2700 feet and live and ride at an elevation of 4700.

I have checked the flywheel and it is tight, no leaks. We are using a mixture of 45:1 using Bell Ray synthetic oil per the previous owners recommendation. The Needle is set to its leanest point. The plug was oil coated and wet even when it was pulled and replaced by the person we bought it from. And the boy riding it was an experienced rider. However the goo out the tailpipe was not there when we got it. Does this tell you anything & any recommendations, please?

Thank You

Hard to guess what the noise might be without actually listening to it. If it needs a top end, and with 6 months on it- it probably does, then plan on doing that and inspecting the lower rod bearing when you have the top end off. The rod should move side-to-side but should have no perceptible up and down play. It can be difficult to move it exactly up and down without getting some side play to confuse matters. Even a 2000 model bike may need a crank rebuild if the air filter wasn't cleaned adequately or if it sucked dirt sometime in the past. I've seen a crank get ruined in as little as 15 minutes once an air filter comes loose or some similar problem resulting in unfiltered air being run through a motor. Then again, they make a bit of noise even when new.


The goo is a jetting issue. Even at 2700 feet, the stock jetting would be too rich unless it was pretty cold outside. At 4700 feet, it's even farther from optimum. The needle position is one of a few ways to alter the fuel/air mixture. The needle position controls one throttle setting. The air screw controls up to 1/8 throttle opening, the pilot jet controls 1/8 to ¼throttle, the needle controls ¼ to ½throttle and the main controls ½to full throttle. There are other variables like the slide cutaway but you should only concern yourself with the airscrew, pilot jet, needle position and the main jet in your attempt to control the spooge.

There are a number of on-line jetting guides and articles. Eric Gorr has a good one on his site at Before you begin any jetting, make certain your silencer is on good condition (silencer packing fresh and the core holes are clear and unobstructed). A silencer in need of repacking will give rich symptoms.

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Lighting A TTR
Do you know of any lighting kit that can be adapted to a 1999 Yamaha TTR 225? I know of a company that makes them for the 2000 -2001 models but can not locate a set for the 1999 Model. If not what is the capacity of the bikes electrical system. Can it sustain a lighting package as is or does the alternator system need to be beef up.

Thanks - Len

I would check with Baja Designs for some possible options. I know they do a number of different lighting kits and do stator mods and rewinding. I believe their website is at

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Butterfly Powervalve
I have a 1986 CR125R, that I just bought and I'm currently rebuilding the motor. My question is about the butterfly style power valve system. When I got the bike the little coin shaped piece of metal that bolts onto the shaft in pipe which opens and closes the exhaust from the canister (that hangs off the pipe), was missing, but I got the missing piece and now I need to know how to set the valve for the proper open and closing times?

Thanks: Jesse

One of the best investments you can make for your bike is a shop manual. This will give exploded views and specifications and torque specs that are critical.

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New XR Burning Oil
Hi I own a 2001 Honda XR 650 l and I've had it for only 1 month, and it seems to be burning oil already. I broke the engine in softly and got my first service at 1500km, which included oil change, filter change, etc. since then I have ridden it relatively softly, but it's a new bike so it shouldn't matter. It now has close to 3000km on it. Any answer will help


Any number of things may have happened. I would try to get as accurate a number of actual usage as you can. How far do you go before it needs a ½quart of oil? You need to be as consistent in the method of checking the oil as you can. Be aware of the fact oil expands with temp and can affect your readings. The oil level can vary substantially from cold to operating temp. The oil level needs to be at the full mark when it is at operating temperature. Once you get an actual distance number of usage, then go to your dealer and explain the situation with the facts you have. This will go a long way in getting the problem remedied.

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No Second Gear

I have a 1987 Honda XR200R. It somehow ran out of oil and second gear went on it. When I try to shift to second it acts like a neutral gear. Can you tell me what I have to fix and or what I should replace

I truly doubt if the lack of oil has anything to do with your 2nd gear problem. The engine would quit running before the transmission would fail. In any case, the gear or the respective shift fork itself is faulty. Either way, the engine needs to come out of the frame and be totally disassembled to get to the gears. Chances are, the dogs (the teeth on the side of the gear that mesh with the corresponding gear next to it) are rounded. You're looking at probably a $500 repair to fix this.

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Bent Disk - No Brakes

I have a 1999 YZ 125 and I have no pressure in my front brake. I have bled the brakes a couple of times I still have no pressure. I had a fall while riding and bent my front disc a little and noticed about 2 hours later when done riding, could that have anything to do with my front brake pads not moving at all and no pressure. I also blew the brake cable out with a compressed air pump. What could be the problem?

The lack of brakes directly after a fall points to a bent disc. But this usually gives a symptom of the brakes pump up fine sitting still and then get soft once the bike is rolled. This is due to the caliper piston being pushed back by the bend in the disc as it passes between the brake pads.

But it sounds like you have something more than this going on. When installing a new brake line, I attach it to the master cylinder but leave the caliper end disconnected first. Pinch the banjo fitting between your fingers while holding the end at a point higher than the master cylinder. You can feel the slightest pressure build when pumping the lever. When you feel a little pressure build, let the pressure go and squeeze the end of the hose again before releasing the lever. This way, you can bleed virtually all the air from the hose itself. Now connect it to the caliper as quickly as you can so you allow the least amount of air into the hose as possible. Have the caliper unbolted from the fork so you can raise it up over the level of the master cylinder.

Now the tricky part. You need to bleed the caliper but you need to hold it so the bleeder screw is at the highest point. You may need a 3rd hand to help squeeze the lever and refill the reservoir as you open and close the bleeder screw. Once you get as much of the air out that way, bolt the caliper to the fork. One method I've had good luck with is to use a screwdriver to spread the pads apart. This pushes the air bubble up the brake hose instead of fighting to get it to go against gravity. Once you spread the pads, pump the lever to extend the piston again. Bleed it through the bleed screw once the caliper is bolted in place to get the last little bit of air out of the caliper. Then keep doing the pad spreading method to get the last of the air out of the hose. This has been the most successful way I've had to get 100% of the air out of the brake system.

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Woods YZ?
Hi Mark. I have a 2001 YZ426F that is just a beast on the track but the problem I am facing is that I want to take it off the track and onto the trails. Can you give me a little advice on what would be the best approach to do this? I have been told to add more flywheel weight but I am not sure how much to add. What about the timing? Can I change the timing to make the bike less YZ like and more WR like? By the way I am 6ft 2in tall and weight 250 lbs.

Any help would be GREATLY appreciated.

Thanks, Jeff

A flywheel weight would be the first place to start. The least amount of weight I'd put on would be 10 ounces. You're better off with 12 or even more. The weight won't slow the bike down; it will just slow its tendency to rev out so quickly. It'll help allow it to get traction with the rear tire easier and in more adverse conditions. I'd be surprised if you wanted to take the weight off for motocross use after you've ridden it with the weight. You could change the cam timing to WR specs but I think I'd do that as a last resort.

One problem with using a YZ in the woods is the tall first gear. You might try a one tooth smaller front sprocket to bring the gear ratios into a more useable range. That way, you'd get a substantial difference and could swap back to the stock front sprocket when you get ready to hit the MX track.

Even with a gearing change, you still may find yourself using the clutch enough to make it need adjusting in some tight sections. Once the clutch cools back off a few degrees, the free play normally returns to where it was. A hydraulic clutch will automatically compensate for this. I've installed a Hebo hydraulic clutch kit on a number of YZ and WR Yamahas with excellent results. One side benefit is greatly reduced clutch lever pull. Hebo is the supplier for Gas Gas OEM hydraulic clutch components. Your local Gas Gas dealer should be able to order the universal kit through their accessory division.

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Gotta Go Faster
Hi, I just bought a 97 KX 250, it's mechanically great, and plenty fast for me. But, I for some reason want it to be faster. How much help would Boyesen reeds make? Or if you have any other suggestions please let me know.

Thanks, Jeff

Personally, I've had truly remarkable results using the V-Force reed cage. The only mods I've done that give a larger increase in overall power are either a major cylinder porting or a big bore kit.

The V-Force reed cage comes with an adjustable reed stop. I've found the low-tension setting is preferred by virtually all riders. This gives a substantial increase over the entire rev range. The key to getting full benefit from the V-Force reed is to lean the jetting once the reed is installed. You'll need to lean the jetting across the entire range (pilot, needle and main). In my opinion (and I'm not paid or compensated by V-Force), once jetted, dollar for dollar, this is the best single mod you can do to a two stroke.

Otherwise, the sky is the limit concerning mods. A quality porting can make a big difference, not just in peak power but also to alter the power output to meet your desires and riding style. A 2mm overbore makes a big difference but then you're starting to get into spending a good chunk of change. Boring and replating can run into the $400+ range (including the piston kit) not including labor to remove and install your cylinder.

Obviously, a pipe and silencer can give a substantial increase. And just like the reeds, the jetting needs to be fine tuned to get the full benefit.

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Clutchless In PA
Hey mark, I got a problem. I noticed a leak in the clutch cover on my 1997 YZ 125. After searching for all cracks and problems I found a loose oil check bolt. Here's the problem: as soon as I put the clutch back together, the cable had no resistance. I think I hooked the cable back up right, according to the manual. Everything looks fine I just wondered if u could give me some advice. Thanks!

Pissed in PA, Pounder

There is a rack type gear sticking out of the center of the clutch that has to engage with the actuating shaft in the clutch cover. If you get it a tooth off, it'll give the symptoms you have. There is actually a set of marks on the side cover that should line up with the end of the actuating arm when everything is timed correctly. The end of the arm is at a slight point and that should ride directly between the two ridges cast into the cover below the arm (where the cable hooks to it).

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Jetting - 2000 YZ125
What are some example Carb Jet settings for a YZ 125/ 2000 With a 10-75 Jet needle, and a #480 Main Jet. I just put those in because of Pro Circuit Platinum pipe and 304 Shorty Silencer. Runs rough on low end, top end pulsates so to speak, when I hold the throttle full open. Was wondering if there are certain adjustments to each jet that will work for sure. Thanks.

Jarad, El Cajon, CA

There are way too many variables to give exact numbers but I've been using 430 or 440 mains (about 1000 ft elevation) with a pilot in the 27.5 range. Needle position set for crispest throttle response. First of all, your main is way too rich. Before doing any jetting, make sure the reeds are in good condition, the float level is correct and the silencer is not in need of repacking. Even a fairly new silencer may need repacking if the packing gets saturated or the holes get glazed over.

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Year: 1999
Make: Honda
Model: XR600R

I recently purchased my Honda. On the first crack of the throttle, it hesitates or cuts out. I have a 1982 XR500R that rips off the line quicker. The 500 is stock with a K&N air filter. The 600 is also bone stock with the end cap of muffler taken out. The only thing I have tried is to lower the clip on the needle with not much change. Am I just twisting the throttle too fast to start? Are there any mods I can make to remedy this annoying problem?


Colorado Springs, Co


The needle position controls the jetting at ¼ to ½ throttle settings, not right off idle. You can try a couple things pretty easily. One is to try adjusting the mixture screw. Try richening it up about ¼turn at a time. If that doesn't give satisfactory results, you might try raising the idle speed up just a little. This can help reduce/eliminate the hesitation. Otherwise, you might need a richer pilot jet.

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Broken Gears
I have a 1988 CR 250 and one day when I was on a ride the clutch just stopped to work. When I was pulling the clutch there was nothing, no pressure anything. So I figured I would drive home without - at one point the transmission jammed in third. The two gear (of the third one) the one on the main shaft blew in small pieces and the other one ripped a dog. Also the shifter fork shaft bent a lot. So now before I order the parts I want to know what could have done this cause I have no idea and I don't want it to **** up back the first ride I take with it.

Seems fairly obvious that something broke off and got wedged in between something else. Just what came first is hard to tell. Sort of the "What came first- the chicken or the egg?" type thing. As long as you have replaced all damaged parts and have thoroughly cleaned out the bottom end, you should be fine. Whatever broke the gears was a relatively big piece- not a small metal shaving.

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The front brake on my '95 KX 250 is sticking. The wheel turns when I ride the bike but when I put it on a stand and try to spin the front wheel it's almost locked in place. I flushed - the brake still sticks. Any suggestions on how to fix my problem will be greatly appreciated.


Sounds like you may have the master cylinder push rod clearance adjusted too tight or the piston itself isn't returning. You need to verify that you have some free play in between the lever and the master cylinder piston/pushrod. If it isn't returning 100%, then it will do exactly what you're experiencing. There is a return port inside the master cylinder that won't release the hydraulic pressure if it is covered. This is in the last millimeter or so of the piston travel.

I have seen an unusual circumstance that gave the same problem. There is a small rubber boot right at the end of the master cylinder where the pushrod goes in. This prevents dirt and grime from getting in to the guts of the master cylinder. Some rubber boots have a small metal circlips made into the outer edge of the boot. I ran into a KTM that had this circlips out of place and holding the piston pushed in about 1mm. This was all it took to lock up the front wheel after a short ride.

The one way to verify if the source of the binding is mechanical or hydraulic is to open the bleeder screw. If the release of hydraulic pressure frees up the wheel, then you know the problem is at the master cylinder. If not, you have a slider that may be bent or some other issue at the caliper.

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Low End Bog
I have a 01 WR 426 that I'm having problems with the jetting. First of all I have removed the exhaust baffle/plug and the top of the air box. I have also had the throttle stop filed down to YZF specs. The dealership that I bought the bike from rejetted the bike stock with the baffle, box top left on to a 155 main jet and they leaned the needle one position.

I have since tried an infinite number of jetting combinations to compensate for the increase in airflow. The problem I am having is a bog or engine cut out at about quarter throttle when the throttle is opened quickly. Sometimes if the throttle is opened quickly and is held at quarter throttle the engine will actually die. I have tried many main jet settings in combination with pilot jets, needle position, airscrew adjustments trying to keep the main jet as a constant while checking the other settings. Then changing the main jet and doing it all over again.

I now own every jet and needle made for this bike!!!!! I can't seem to get rid of the bog. It is very frustrating when you need a quick burst of power and its not there just about sending you over the bars when it cuts out!!! The problem seems to be slightly more noticeable when you have the bike slightly lugged down in a taller gear and snap the throttle open.

I live and ride in Washington at usually 0-4000 ft. and would love some advise. The bike runs like a champ once you get past the bog. I know there is an answer! PLEASE HELP!!


Seems you've eliminated jetting as the problem. I think I'd start investigating other areas like the accelerator pump.

Does the bike run normally with the baffle and air box top installed?

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Pinging TTR

I just purchased a new 01' TTR225. Low-end power seems fine. But when I get up around 1/2 throttle it begins to ping and sounds like it is breaking up. Yamaha suggests a 10 hr. break in period. I have about 6 hrs. on it now. I have been waiting to see if it gets better as it gets more broken in. I brought it back to the dealer twice and basically they rode it around for a few minutes and said it was fine.

Am I nuts? This would be nice.

Thank you Chip

No, your 225 should run fine all the way up to redline rpm. You shouldn't rev it that high yet since you can create oil-burning issues later in the life of the bike if proper break in isn't followed. But it should still run okay. It shouldn't ping at all. I'm assuming you're using a decent fuel like any readily available premium unleaded pump gas. The carb float level being too low can give the exact symptoms you describe. If your local dealer isn't any more cooperative than that, a call to the regional corporate Yamaha office may get the ball rolling.

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Rattling RM
Hello I have a RM 465 I'm also getting a rattling noise at an idle. The motor has been completely rebuilt I hope this has nothing to do with the bottom end. The bike is loud and vibrates so it's hard to tell what it is. You were giving advice to someone else about using ATF type F in the tranny. can you do this on this model and what are the benefits of ATF.



When you say the motor has been completely rebuilt, do you mean the bottom end also? Were the crank bearings replaced? Does the noise go away when the clutch lever is pulled in? Are the motor mount bolts adequately tight? Was it rebored and a new piston installed? Are you certain the people who bored the cylinder set eh piston/cylinder clearance properly?

Type F ATF is a good lubricant that can make a good shifting bike shift even better. It can improve clutch feel and action. Your 465 will do just fine with the ATF. Like any other two-stroke, just keep the fluid fresh by changing it frequently. This needs to be done whether you use ATF or any other oil.

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Thinner Gaskets?

I have a 2000 XR400R and have been looking for a source for a gasket kit that will increase my compression by decreasing the thickness of the gaskets.

What company is the best source for such kits?

Thanks, Hans

Cometic makes high compression gasket kits for two strokes. I don't have a Cometic catalog but I do know they can, and will, make any gasket any thickness out of any material you need. A call to Cometic should get you what you need.

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Shock Valving Diagram
I am looking for a detailed diagram of the valving in my 1991 Honda CR125 rear shock. I need to know the stacking of the washers, piston, seal, etc. If you have this information available could you please contact me, or if you know where I might look I would appreciate that information also.

Thanks, Mike


I don't know of anywhere that those specs might be listed. What are you trying to accomplish? Are you trying to reassemble a basket of loose parts? Are you trying to revalve the stock shock? I may be able to get you some good info if I know exactly what you're trying to achieve.

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New Reeds, No Bottom
This winter I put the new v-force delta 2 reeds in my bike thinking it would make it more explosive, well in return I don't have any low end. The reeds are adjustable so I expanded the reeds out as far as possible because when they were closed tighter there was no bottom to it. It made the mid and high range feel great but it is a dog until then. Did I do the right thing by opening the reeds up as far as possible and what else could I do to make some more low-end? Thanks


I'm not sure what you mean by "opening " the reeds up. The stop plate is adjustable. You need to set it on the low-tension setting. This is the only adjustment possible on that, or any reed.

If you didn't notice a substantial improvement with that reed set up, then one of two things is going on. One is you didn't rejet to compensate for the reed cage or two; you have some basic mechanical issues that need to be corrected. Something like the power valve stuck in the open position maybe.

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Good Spark & Compression But Will Not Start
I have a 2000 CR250 which will not start. The bike is getting fuel, has a good spark, and has a lot of compression. When it ran, it had as much power as it did when it was new.

2 weeks ago I tore the bike apart and put in a new piston and rings because I was told that it needed a new top end and that's why it won't run. I noticed that the stock rings were in their grooves when I removed the cylinder. I showed the head and cylinder to a mechanic and he said everything looks good with the parts. So I put the bike together and it fired up on the first kick.

The bike ran great for 2 weeks. I broke in the piston and rings correctly and put on about 30 easy miles on the bike, and then it would not start again. There were no strange sounds coming from the engine when it ran.

The bike has plenty of compression when you try to kick it over and it will not even start when you try to roll start it. The bike has very few total hours on it and I only trail ride it. I also run my oil at 40 to 1. Could this be an electrical problem? If so, how can I fix it?

Thank you, Mark

If it were an electrical problem, it must be delivering spark at the wrong time (since you say it has a good spark). Normally this would give some backfiring or sporadic popping when you try to kick it over.

Are there any rags in the air box (I've been bit by that one before)? Is the exhaust plugged? Did any 5-year-old hands put their favorite toy in the silencer? Is it getting too much fuel? If the float needle isn't shutting off the fuel flow, it may just be way too rich and is flooding and gas fouling the spark plug.

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Pops On Top
Hi, I have a 2001 KX 65 and it pops on the top end at 95% or so there's still a little bit left I run VP race fuel, pump gas 50-50, and mix it at 32-1 with castrol oil. The dealership says its out of time, so I adjusted it and played with it but it still does it. Do need to get a pipe? A KTM? This isn't the only KX 65 I've heard doing this. My son rides this thing wide open - pinned at times - is this bike not gonna handle it? Also when I set the airmix screw that if the bike doesn't idle it has better response?

Thank u, Chris

The timing is fine. Oops, sorry, it was fine. The popping is a fuel/air mixture issue. Chances are you have an air leak somewhere. I'd do a crankcase pressure test. Be sure to check the transmission vent hose for pressure when doing the test. This would indicate the center case joint is leaking.

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Yamaha XT 250, 2000 model.
I'm from Australia and we have some fairly rough terrain, the problem with my bike is that it bottoms out too much on small jumps and hill descents.

What can I do to improve the suspension (front and rear) without spending too much time and money?

Thanks, Eddie

I'm not familiar with the XT 250 specifically. The thing I'm not sure of is the suspension adjustments. If the rear spring preload is adjustable, setting that for your weight would be the first place to start. Increasing compression damping settings would also be one of the first things to do.

The forks can be improved immensely by simply adding more oil to them. Use a syringe and add 10ccs of 5-wt fork oil to each leg until the bottoming has been reduced to an acceptable level. You may have to add 30 or 40 ccs. The oil level from the factory is generally somewhere within a wide range. Changing the oil so you know the oil is fresh and you know the oil level would be a good idea but you can do the adding oil trick very easily. You'll have to remove the fork cap to add the oil. Loosen the top triple clamp pinch bolts before you try to loosen the fork caps.

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How Much Oil?
Hi, I was wondering how much oil should I put in the gearbox and what kind for a 1989 Yamaha YZ80???

It should have the oil quantity cast into the side cover right next to the oil filler cap. It should be in the 650ccs range (about 2/3 of a quart). You can use any number of different oils. Everything from the high dollar two-stroke gear lubes (not my first choice) to automotive Type F Automatic Transmission Fluid. The owner's manual lists a specification for automotive engine oils. So you can use auto engine oil, Type F ATF, or the specialty gear oil. Whatever you choose to use, I'd recommend changing it frequently. This means the $1.50 a quart Type F is by far a much more cost effective choice than the $8 per quart gear lubes.

You'll be fine simply using thicker weight auto engine oil, such as Castrol 20w50, or something similar. Just be sure to change it frequently.

MX Tuner

Frozen Fork
Hi, I have a 1989 Yamaha YZ80 and the front suspension fork is stuck at half way point and wont go up or down at all, what do I do???

Sounds like you have a large dent in one of the fork tubes. If you look at the lower part of the leg, you'll probably find a fairly large area where it has taken an impact. Once you get the forks extended, you'll have to replace the damaged part. There isn't any way to repair something like that properly.

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Hello, I own a 1985 KX125 and I need new plastics and such. I was wondering if there any newer years that I can buy plastics for that will fit my bike and give it a newer look?

Nothing but what is designed to fit your year model bike will fit properly, if at all.


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I own a 1994 CR250. When ridding mid to full throttle I get this noise that sounds like a handful of rocks hitting my front fender. I had Eric Gorr port the cylinder and I used a cometic high compression gasket set with a vertex piston. I am running a 1370 needle in position 4 and a 175 main with a 55 pilot. Air filter and silencer are both fresh. I check the resistance on the coil and stator everything was in spec. I cleaned them and put dielectric grease on all the connectors. I run 94 octane with Maxima 927 @ 40.1.I am running out of things to try I don't think its compression because it's not high pitched pinging. Its like um like I said a handful of rocks hitting the front fender. Please help.

Chances are you're hearing some detonation. The high compression gasket kit is a good mod for a stock head and cylinder. Once you get the higher than stock gasket set combined with 94 octane, you get a very good possibility of detonation.

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Busted Housing
I just rebuilt my 91 RM 125 and I hit the drain plug and busted 1/3 of the housing of where the drain plug goes in and I stripped it when I tried to tighten it. We put a liquid substance around it that turns into aluminum (it still barely leaks). I was wondering if I have to split the case to fix it.

It depends on how good of a welder you can find as to whether it can be fixed at all. That can be very difficult to repair. Your chances increase dramatically if you have the piece that broke off. Otherwise, yes you'll have to split the cases to do a job worth attempting.

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I Need Some Help Here, Please?
I have a Suzuki 1996 RM 125. When you start the bike it revs up very fast and smokes a lot - thick white smoke, then after 20 to 30 seconds slows down. You have to gun it to keep it cleaned out then it idles fairly good. It fouls the plug in about 1/2 to 1 mile of riding. Not normal by far.

It has a new piston and ring. Cylinder looks good. I use hi test pump gas and Yamaha 2-cycle oil 32 to 1. The plug comes out very oily somewhat black. Carb has a 170 main jet, and the needle is the right one for the carb and the clip is at the top not on the third one like the books says no improvement.

Has a new needle valve for fuel shut off. Reeds are closed, exhaust is open, and all look good. Does not have a front-wheel-popping get up and go.

Can crank case oil get into the cylinder from bad seals? Is the carb leaking gas into the crankcase we turn off the gas when not in use. Oil mixture, wrong? Too big a jet, need to run racing fuel? Am at a loss and out of spark plugs.

Any advise please. Tony


Sounds like you may have a right side crank seal leaking gear oil into the bottom end. This would be the most likely thing causing your symptoms. Doing an accurate crankcase pressure test can be more involved than simply changing your right side crank seal.

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Sparkless Wonder
I have a '92 ATK 406 and the ignition system has stopped making a spark. I've checked all the connections to the coil, plug, and stator, and they are clean and tight. I checked for shorts to ground and there were none. Could you tell me what the resistance should read for the primary and secondary stages of the coil? Also, is there some test I can do with a millimeter to check the stator output? The local dealer only suggests bringing it in, and I'd rather fix the problem myself than to pay someone to do it. Thanks


There are specs for resistance values between certain terminals but those will only be listed in an ATK service manual. I'd suggest buying the manual yourself and then all you'll need is a digital volt/ohmmeter to test it yourself.

Just remember that the specs and any readings you get have to be taken with a grain of salt. In other words, if they call for a spec of 250 ohms max and you get 261 ohms, then I don't think that much over the limit would be enough to condemn the part. Due to the sensitivity of a decent volt/ohmmeter, the readings can vary due to normal added resistance from dirty connectors and such. By the same token, you can have a component that checks exactly right and is still faulty.

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Going Buggy!
Hi I have a Yamaha XT 225 in my Beach Buggy (Tipan.)

Last weekend I was driving and all was goin well until the chain fell off and I had to stop the engine. After fixing up the chain, I started the engine the idle was fine but as soon as I put some throttle on it starts to thump and not rev out as it did before. But the weird thing is the idle is perfect.

I have checked the timing and its fine; I have cleaned out the carby and no hope there. Changed the plug.

Today I was trying to fix it. As the engine was running I moved the carby around and holding at a position the engine was running perfect but as soon as I let go of the carby it went back to the thumping and low revs.

Can you please help what could it be. Oh, another thing - where is the high-end pilot jet??


Sounds like you have a torn intake boot or some other air leak at the carb. Look closely at the rubber boot that the carb attaches to.

I'm not sure what you're asking about the "high end pilot jet". The pilot jet is located in the bottom of the carb but that controls a low speed/low throttle opening circuit. The main jet (also located in the bottom of the carb) controls the high-speed circuits.

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