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.

Pricy Engine Oil?

I'm new to riding and recently purchased a Suzuki DS 400S dual-sport, which will primarily be ridden on fire roads. The cycle shop recommended Honda's engine oil. Is this pricey 10-40w oil truly worth the extra expense?-Mobil 1 synthetic would be cheaper! Also, what's your advice on frequency of oil changes. Thanks for your help.

Mike Edmunds

This is one of the most controversial subjects I've seen. My WR 450 lives on a regular diet of Mobil 1 15w50. You can use a non-synthetic automotive oil with no problems whatsoever. You need to stay away from oils with the "energy conserving" rating in the circle. They add friction modifiers to make them energy conserving. These additives can contribute to a wet clutch failing prematurely. All the Mobil 1 synthetics have the energy conserving rating except for the 15w50. The motorcycle oils do NOT lubricate any better or stand up any better to shear from transmission gears than auto oils.

Changing your oil frequently is as important as choosing a good oil. This is one thing you can do to help determine the life of your motor. My Yamaha oil comes out looking just like it goes in. You would do better using a non-synthetic auto oil and changing it more frequently than using the motorcycle oil and trying to stretch the intervals out.

MX Tuner

Plug Fouling

I have read your recent response to Neal Manalo about proper starting procedures and spark plug fouling. I have a 1979 CR250R that has an engine rebuild twice now and I am still having problems with keeping it running and fouling plugs. I have purchased the correct plug from the Honda dealer and it lasted a short couple of hours. I crossed referenced it with NGK, Autolite, Champion and every other brand I can get my hands on. I ride on the dunes with a paddle tire on it. The engine was running hot after about a half and hour and started making a knocking noise. I has become hard to start and every time I put in a new plug it seems to short out and refuse to spark after a 2 to 5 minute run. This doesn't give me much running time.

Any suggestions other than carry a dozen plugs and a wrench? The plugs come out wet and black the tips are generally dirty and the electrode cleans up with a wire brushing. What is the proper plug for the sand and if I switch over to the local trails and change the tire to a trail type?

What is the recommended jetting for this bike. I think I could do better with power and acceleration if I knew what to change it to. My dad is handy with tools and has been a big help tearing this thing down and rebuilding every three months. This is my first bike so I'm learning. Learning it takes more money to enjoy this sport than I can earn mowing lawns for the neighbors.

Luke Stewart

It almost sounds like a couple different things happening at once. If it has developed an air leak, that could make it run hot. One possibility is the flywheel side crank seal. Concerning the plug fouling that quickly, if it is sucking gear oil, it could foul plugs in that manner. Sounds like the bottom end might be worn out. I'd remove the flywheel cover and try to move the flywheel up and down. If there is any movement up and down, this could account for all your problems. One seal is sucking air and the other is sucking oil.

Assuming you aren't running the engine in too low of a part of the rpm range, the standard plug should work okay for everything. For the dunes you might want to go a step richer on the main jet.

There are too many variables for anyone to give you specific numbers. Jetting is basically trial and error. The only real worry you should have with trying different jetting is going too lean on the main jet. Otherwise, just remember the golden rule of jetting - only make one change at a time. Start with the pilot jet, move to the needle position and then the main jet once you're satisfied the lower speed circuits are okay. On a bike that old, you need to be aware some carb parts can wear which will affect jetting. The needle jet and jet needle can both wear richening up the mixture. Trying to jet with these worn parts can get you chasing your tail.

You're one up on me. I had to learn on my own. My dad is the most un-mechanically inclined guy on the face of the earth. But the lessons will last a lifetime. Ask questions before you spend money. Find someone you can trust for good advice. Normally a parts guy is one of the last people you can trust for *good* advice. Not because they want to sell you parts you don't need but because they don't know the right answers. Why do you think they are parts people and not mechanics?

MX Tuner

Smoking KDX

I just got a 86 KDX 200. I have never rode a dirtbike before. After I ride I have some oil residue on the outside of my pipe and if I touch under the fender I see oil all over my hand. I don't think this is normal? This bike was all rebuilt according to the guy who sold it to me. The guy said since its a new head gasket he put more oil then needed in the mix and this is one of those guys who buys a bike then sells it so it wasn't ridden by him. When I got the bike home it was smoking like crazy but when I made a mix and weakened it a little it stopped smoking hard. I was wondering if these bike are supposed to smoke a bit. It gives some smoke still out of the exhaust.

Johnny

Normal, yes. Do you have to live with it? No.

One of the bigger contributing factors is how hard you're running it. The harder you run it, the less spooge you'll get out the exhaust. Since running it a lot harder may be hazardous to your health, the next best thing is to run a hotter spark plug. I'd run a B7ES plug. This will greatly reduce the amount of oil coming out the exhaust.

One other possibility is if you have a right side crank seal sucking gear oil. Monitor the gear oil level. If it drops significantly, you may have a crank seal going bad.

MX Tuner

XR250 Forks

My bike: 1992 Honda XR250RN.
Problem: Don't feel comfortable with the suspension.
Terrain: Enduro type, woods, some mud, loose sand, non paved roads, rocks, a lot of climbing.
Symptoms: the bike is hard to turn like if it keeps going straight, or if I turn too much, then it looses contact & feels slippery.
Questions:

1. How much oil (qty.) should each fork have.
2. What can I adjust?
3. How much air pressure.
4. For the rear shock, should I do something?

Thank you beforehand.
R. Ludlow

Standard oil height is 120mm. This is measured with the fork fully compressed without the spring.

You can adjust oil height and weight. If you weigh more than about 160lbs, I'd run the oil level a little higher. Try about 105mm. Thicker oil will make it stiffer all the way through the travel but will also make it less plush on sharp edged bumps.

Air Pressure should be 0 psi. The air fitting is to release built up pressure. Be sure and do this only with the forks fully extended (bike on a crate type stand).

Any adjustments to your rear shock depend on what your complaints are. It's safe to assume the shock hasn't been serviced in a while. This means having the shock disassembled, inspected, cleaned and fresh oil put in and a recharge of nitrogen. This can do wonders for a shock that has old oil in it. The spring rate and preload can make a big difference in the ride. Setting the preload for your weight and measuring the static sag will tell you if the spring is correct for your weight. You should have between 15mm and 25mm of static sag if the spring is right for your weight.

MX Tuner

Mods for XR200

Hope you can help me out as info is hard to come by down here in Veracruz, Mexico. I have a Honda XR200R 1998 bike. I would really like to gain some "free" power as I am no longer a "middle weight". I usually perform any modifications one at a time and verify the results. What are your thoughts on the following: "Uncork" the stock muffler by removing the baffle. Next, discard the air-cleaner box lid or "snorkel". What type of jetting would I be advised to use if these modifications are done? Could I get away with lowering the clip and raising the needle a notch or two, or would I have to change the main jet size? How should I do the "plug chop" to get a consistent and verifiable reading? The weather I ride in is Tropical (high humidity and temperatures in the 80's to 100's).

My riding is down at or very near sea level. I generally ride on sandy beaches and loamy soil trails and some highway (brief) sections. Should I run a colder plug? Bottom line, are the modifications worth it or should I just save up and buy an XR250 or 400? Thanks for your help! Free tacos next time you're in town!

Regards,
Michael Strah

Removing the air box lid and the baffle will help it breathe. Don't expect any huge improvements even if you rejet.

You need to find a long stretch of flat road, preferably with a slight uphill slant. Don't use a brand new plug. You want some deposits on the plug so it'll change color relatively quickly. Carry a plug socket with you. Get up to full throttle in top gear and let it run at high rpm for as long as the road allows. Pull in the clutch, let the throttle return and push the kill button. Once you coast to a stop, remove the spark plug and examine the porcelain.

Under your riding conditions do not use a colder plug. If you were running in nothing but dry sand, then you might go to a colder plug.

The 200 will never be half the bike the bigger XRs are. You can get many more aftermarket hop up parts for the 250 and 400 than are available for the 200. If you start trying to make the 200 do things it wasn't designed for, it'll start rewarding you with some costly repair bills. The 200 is a great bike for what it was designed to do.

MX Tuner

Sputtering YZ 125

I just bought a 1991 YZ 125 and I have had it for about 2 months. I bought it for $2000. Anyway I blew the crank bearings and melted the piston and wrecked the rings. I put new crank bearings and a new piston and rings in it and I got a sleeve pressed in it and bored out to stock measurements. It ran fine for a while until a week ago when I was cruising down a trail and I went to punch it and the power band started to sputter! so I rode it home and I took the carb apart and cleaned all the jets and I checked everything. I cleaned the air filter and tried it again but it still did it! Someone told me that it could be a power valve but I didn't think so. So what advice do you have for me and what do you think I should do ???

Paul Lato

A stuck power valve can give some unusual symptoms. I'd definitely check to see if it is opening. Any exhaust restriction can cause erratic running. Check your silencer to make sure the inner core hasn't broken loose.

Have you tried a new spark plug? I've seen a plug give some pretty bizarre symptoms.

MX Tuner

WR 500 Detonation

I have a 1992 WR 500 Yamaha. I am having problems with pre detonation.. I use race gas.. I understand there is a head modification.. If you have the specs on that or could help me in any way I would appreciate it. I belong to the Big Bear trail riders..

Thanks again Roger Kiefer

The big bore air cooled YZ's benefitted from having the head machined to alter the squish band. There are a number of qualified people who can do this. Whether you can get any of them to reveal their numbers is another issue. You might try contacting Eric Gorr for some info on the specifics of the mods. Check his site at www.eric-gorr.com

MX Tuner

Mods for XT 225

First off, probably like most everyone, thanks for a great web site. You all have a lot of good information here.

My wife and I have been into dirt bikes and four wheelers for a long time and enjoy it alot. Recently we bought a couple of dual sport bikes. Mine is a DR 350 and hers is a XT 225. There are all kinds of readily available hop ups for the DR, but I have had a hard time finding anything for the XT 225. My wifi is only 4'11" and the XT is the biggest bike we could find that she could even remotly touch the ground on. The suspension is ok but the motor is weak. It is in great mechanical shape, it's just real weak. She is a really good rider and needs more power, as much as she can get. I just wanted to see if you have herd of any to help her. I am not sure of any of the engine specs., wheather it has enough room to bore and stroke it or not. Any suggestions would be greatly appreciated.

Thank you
Chris Adkins

I haven't seen any aftermarket parts available for the XT 225. Looks like almost anything you do to it is going to be along the lines of custom parts. Porting the head will only give marginal (and pricey) improvements, especially with the stock intake and exhaust. First thing I'd check into is getting a higher flowing exhaust. Have you removed the baffle? Obviously, this will mean more noise also. A bigger carb can also make a substantial improvement.

One thing to consider is what Yamaha intended the bike for. If you start making mods like you want, and your wife does ride it harder, this will put more stress on the entire bike than it was designed for. This means a bike that still won't do what you want properly and it will be breaking more due to not being used the way it was designed. I'd seriously look at a more capable bike and then having the suspension lowered *correctly*. This will involve installing spacers inside the shock and forks and using shorter springs. This is the only proper way to lower a bike significantly and not adversely affect the handling. The front and the rear need to be lowered the same amount. I've seen some suspension shops who don't do this correctly but still charge the big bucks for what they do. Check with Jeremy at MX Tech. He's among the best in the business. Go to www.mx-tech.com for more info. Jer will set you straight on what to expect.

This will most assuredly be the more expensive of the options you have but will give far better results than any amount of money spent in mods will bring from the XT.

MX Tuner

Seized CR

I have a 1986 Honda CR 125. About two weeks ago I was riding and it quit on me. It had no compression so I pulled the cylinder off to find out that it over heated. The problem is I have chunks of piston all over the head. I want to know if I can get rid of this or if I have to buy a new head. I talked to a few people and they said I could get away with taking a carbon fiber tip to it and taking it off.

Valerie

First of all, we need to get our terminology straight. The head is the part that bolts to the top of the cylinder. The cylinder is the part the piston goes up and down in. Normally, when a seizure occurs, the cylinder can get aluminum stuck to it. I think this is what you're describing.

There are two ways of going about this. One is having the cylinder bored and using the next size larger piston. This would probably be a good idea if it has been a long time since this was last done. With a steel liner, normal periodic maintenance includes boring when the clearances get too large. You may be able to kill two birds with one stone since you can fix the seizure-related damage and do your periodic maintenance all at once.

The other way to address the stuck pieces of piston are to use muriatic acid to remove the aluminum residue. Muriatic acid is readily available at most hardware stores or pool supply stores. This is nasty stuff so be very careful. I know safety experts recommend using safety glasses and thick rubber gloves for just about anything short of brushing your teeth, but you *really* do need to when using muriatic acid (and be sure to do this in a VERY well ventilated area). Pour a little into a small plastic container (that you don't value too much) and use a small wire brush dipped in the acid to brush it on to the residue in the cylinder bore. You'll see it bubbling up almost instantly (showing that it is dissolving the aluminum). Keep applying the acid and brushing it until all the aluminum is gone. This is the best method for saving a plated (non-borable) cylinder after a seizure. Just be aware that the acid will eat any and all aluminum surfaces it sets on for more than a second or two. This includes gasket surfaces.

The only problem with using the acid method is then you're still using the same cylinder bore. If the bore was worn before the seizure, it will still be worn when you install the new piston. Boring to the next oversize will eliminate this problem.

Next thing you need to do is figure out why it seized in the first place. Did it overheat? Was it lack of lubrication?

MX Tuner

4-Stroke Detonation

My XR650L Is having a bit of detonation and pop on throttle roll-off. I'm running a White Bros E series pipe with about ten or eleven discs, a 152 pilot, and a 160 main. I'm wondering if you can give a bit of advice- is it the needle maybe? My mechanic tells me that a little detonation is normal, and not a big deal, but now I heard about a guy who fried his top end b/c of that, so thought to get a second opinion.

Detonation does have the ability to do major engine damage. It sounds like you may have an air leak somewhere. This could give the exact symptoms you have. But that many discs could also contribute to that. Try running 8 discs and see if that helps. My WR400 did the same thing until I removed a couple discs. You could rejet to compensate, but you'll be giving up low and midrange for high rpm power with the larger number of discs.

MX Tuner

Sparkless YZ

I have a 1989 yamaha YZ-125, it has no spark, I am trying to dignose the problem, I dont know if it is the cdi the coil or the stator or just a wire, how do I determine the problem?

Sam

The Yamaha manual should be very clear on resistance values between certain electrical connectors for the entire ignition system. Using a digital ohmmeter (available at Radio Shack for about $20 or so), the manual will give specific color code identification for the wires to be checked and the resistance values you should get if everything is okay. You could have a corrosion problem where the coil grounds to the frame. The ignition coil mounting tabs are a common place for rust to form and cause problems. Remove the coil and make sure the frame tabs it mounts to are clean and free of paint and corrosion. This can give a variety of symptoms (even intermittent spark plug fouling).

MX Tuner

Am I Lean?

I recently acquired a 1993 CR500 and a 1989 YZ125 and I'm having concerns about jetting. Especially since both recently received top ends from their previous owners & I'm not about to blow them up soon if I can help it.

They both came from a 3000-3500' elevation, desert climate. I live in Portland, OR at around 300'. I also ride on the coast, in the dunes (30', deep sand) and in the mountains (around 2000', steep, slippery uphills in the winter).

I occasionally wind the CR out to top speed for a few minutes at a time (then the beach ends), and make good use of its power climbing dunes.

I've jetted the CR500 (has FMC pipe) according to the Honda service manual for my elevation, but only changed the main jet. I've left the Yamaha alone since it seems to be fine where it is.

I run Texaco/Chevron 92 octane fuel with Yamaha 2-stroke oil.

The plugs look fine (a little dark on the YZ) but I'm still leery. This was not after a WOT run & shutdown unfortunately.

What do I need to do to be certain I'm not running lean.

Any help is appreciated, even if it's to tell me I'm worrying about nothing.

Eric

No, you have some very valid concerns, especially since they may have been leaned out from the previous owner for his altitude. The most accurate method for checking the main jet (where seizures occur) is to do a "plug chop". This involves finding a long straight that you can run at full throttle for about 1/8 mile or so. Use an almost new spark plug for this test. Carry a plug wrench with you. Once you have reached the end of your straight, pull in the clutch and hit the kill button. Remove the plug and inspect it's porcelain color. Ideally, it'll be a tan to light brown color. Anything approaching white is too lean to be safe and anything darker than chocolate brown is too rich to give good performance.

When it comes time to rejet, you'll need to do the main jet circuit last. Make sure the silencer packing is fresh and not wrapped too tightly. This can have a major affect on low speed jetting. You want to do the lowest speed circuit first and work your way up from there. Start with the pilot jet, Once you have that sorted out, adjust the needle. Then go on to do the main jet. The lower speed circuits overlap with the higher circuits but not vice versa. Adjust the low speed circuits for the best throttle response and the main jet to get a safe insulator color using the plug chop method.

MX Tuner

New KX Questions

I have recently purchased a 2000 Kawasaki KX250 and have some questions. First thing is gas. I live in Northern Ontario, Canada and I'm not too sure how they compare to the States but I was told by the dealer that 92 octane will be fine. When I talk to all the guys who use them they say I need AV gas 100LL or better cause the pump gas will burn up my cylinder.

Also I hear the shifting is bad too but I heard only the 99's were affected.

I was also told to run kx500 clutch springs.

Also what type of oil can I run? I'm thinking about yamalube 2-R synthetic.

Any help is well appreciated.

James

I don't know how Canada rates their fuels. In the US, they have a federally mandated method. This is the yellow sticker on each pump that has the (R+M)/2 printed on it. This means the number listed is an average of the research octane and the motor octane. In your owners manual, they likely recommend a fuel with a minimum octane rating of about 95. This is the research octane number (which is the higher of the two). The US premium unleaded (91 pr 92 octane) fits into this requirement.

The pump fuel won't "burn up" your cylinder. Kawasaki doesn't have very good plating. Even with race fuel, you can have bad spots develop in the cylinder. The aviation fuels are a higher octane but aren't very good for other parameters like throttle response. Octane is one very small piece of the fuel puzzle. Your KX doesn't require a high octane but it sure would like a good quality race fuel. You won't do any damage with the avgas but you won't likely see any big benefits. If you want to feed your KX the best, find a good race fuel, jet for that fuel and stick with it. Even if you mix it 50/50 with pump fuel, you'll be ahead of the game.

I hear the shifting is bad too, but I heard only the 99's were affected.

One of the magazines had something about updating the '99 with a couple '00 shifter pieces. I've never been impressed with any of the magazines technical updates. Have you tried different oils? you can make BIG improvements with some different oils. Try either Mobil 1 15w50 synthetic or Type F automatic transmission fluid. The KXs seem to really do well with the auto transmission fluid. Just keep it changed relatively frequently. If it changes color to a dark color, it is time to change it. A lot of this depends on how hard you use the clutch.

KX 500 clutch springs will give a stiffer clutch pull. Personally, I try to avoid that as much as possible. If you keep the gear oil fresh and use a good quality oil (this does NOT mean you have to use motorcycle specific oil), you shouldn't have any problems out of your clutch.

Yamalube 2R is an excellent choice. It is one of the cleanest burning oils out there. With the power valve setup the KX 250 has, this is critical. Most oils lubricate well nowadays but some can leave significant deposits that can be a pain to live with. Castor based oils (Maxima Super M and the 927) are tops at lubrication protection but the worst as far as deposit accumulations. So if you tear your motors down every week, then that would be my choice. But if you're like 99.9% of the weekend warriors out there, I'd stick with a good synthetic or semi-synthetic.

MX Tuner

RMX Jetting?

Hi I own a 94 Suzuki RMX 250 if I install an aftermarket Answer spark arrester on this bike will I have to rejet, the machine is all stock with a 60-p 150-main. I'm at sea level.

Richard

Chances are, you'll benefit from rejetting even if you don't install a spark arrestor. But yes, the spark arrestor can affect the jetting. One hint with your Keihin carb, The lower you have the idle speed set, the crisper you can get the off-idle throttle response. The 60 pilot is pretty rich. It wouldn't surprise me if you ended up with a much leaner pilot jet.

MX Tuner

Starting Problems

I have a 1990 Honda CR125 It ran awesome and was running great for the first 3 hours of my trail riding, until all of a sudden it started to seem like it had resistance or something in the engine or something. It would rev good and everything, but then when I let off the gas, the engine would stall. It would not idle at all. I don't know if this would have anything to do with it, but about 2 mins before this happened, I was sitting on a steep downhill talking to someone with it not running for like 15 min. Now I cant start it with the kicker, but am able to pop start it, but it still has all that resistance or something and sounds very bad. It fires all good and everything, but makes a noise like when you take a card and run it across a picket fence. I took the spark plug out and it was all dry black, but only like 7 hours on it. What do you think is wrong?

Thanks!

Max

Well, Max. It doesn't sound good. The fact it did it 2 minutes after sitting is coincidence. You've had some kind if internal engine failure. Could be a piston seizure but it could also be a big end rod bearing. I'm hearing a little conflicting info but regardless, it needs to be torn apart and inspected. Look at the sides of the piston. Check for up and down play in the lower end of the connecting rod.

If it is a piston seizure, chances are the cylinder has some aluminum stuck to it. This can be easily removed with muriatic acid and a small wire brush. The acid will attack the aluminum but not the plating of the cylinder. You must be very careful with this method since any residual acid will eat wherever it runs off to, including other parts of the cylinder. Muriatic acid is very caustic. Use it in a well ventilated area with rubber gloves and safety goggles. Nasty stuff. Dip your brush in the acid and rub the cylinder where the aluminum is stuck to it. Keep doing this until the aluminum is removed. You could realistically get this done for about $100-125 in parts if you can do the labor. If this is the case, you need to try to figure out why it seized. Bikes just don't seize for no reason. You don't want to put it together and have it seize again right away.

If the rod bearing is worn, it'll be a much bigger repair. This will require splitting the cases and repairing/replacing the crank. You can get a rod kit for the cranks but you can also get a new crank for about the same price. Do some price shopping before you decide the best way to repair it. Generally, a new crank is better than a rebuilt crank. Check mail order prices and ask local shops if they can install the rod kit. This repair will cost roughly $300-350 in parts plus the labor to install the rod kit and the crank. This could be in the $200-250 range itself. If this is the problem, make sure your air filter and air boot are in good condition. If it is allowing any dirt into the engine, it can drastically reduce the life of these components.

MX Tuner

Oil Leak

I have a 1985 YZ250. it has leaked oil since I bought it. I don't know where the leak is coming from. Recently it started to leak a white, milky fluid. It still ran before I shut it down. I know that water is mixing with the oil, but I don't know what is wrong. Do you have any idea what the problem could be?

MSTGOFAST

If you have coolant mixing with the oil, unless you have a cracked or porous case (pretty rare), the only place that can give this symptom is the water pump seal (pretty common). This is located in the right side cover. When you pull it down, be sure to look closely at the bearings and the water pump shaft. If the bearings have any play in them, they need to be replaced. The water pump seal can cut a groove in the pump shaft. If it has a groove, it must also be replaced. You'll need to change the oil a few times to flush the remainder of the contaminated oil out.

But this shouldn't create an external leak unless the oil (and added coolant) level is high enough to make to come out the transmission breather hose. But this is reaching. Chances are you have a seal leaking or a cracked case somewhere. Try washing your bike and be thorough with the entire motor, especially the bottom half. You'll need it completely clean and dry. If you need to, use some aerosol brake cleaner to make sure it is clean. Let it set and inspect it periodically. If it doesn't leak sitting still, then ride it around for a minute or two. This should help narrow down exactly where it is leaking from.

MX Tuner