Technical Questions? - Ask MX Tuner
Dec. 01, 2001
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.
Top End Power
Generally speaking, a worn out top end will only run relatively well at higher RPMs. There are specs for checking the ignition system components. There are resistance readings for checking wires going to each component. They will show the wire colors, where to check and what the reading should be. But be careful. The readings should be taken with a grain of salt. If a spec is for say, 250 ohms and you get 255 ohms, that doesn't necessarily rule that component as being "bad". And by the same token, if it reads dead within the spec range, that doesn't mean the component is good. It still might be faulty. The only true way to check an ignition component is to swap it with a known good unit.
New guy solutions:
I can kick all day sometimes and nothing. I will let it sit for a day and 3 or 4 kicks and it starts right up. I run 40:1 gas mix. It has a FMF expansion chamber and spark arrestor. I believe everything else is stock. That's what the previous owner told me anyway. I have decent mechanical skills with autos but never have worked on a bike. The bike has been ridden a lot it looks like. I know it needs work but where do I start to get it to consistently start. I know there are probably a few hundred things to look for first, all I'm asking for is a few. Thanks for your time.
Geoff - Southeastern Michigan
Your starting technique may need some fine-tuning. Sounds like you have either an air leak, some carburetor jetting issues or a combination of both. Once you get these issues straightened out, you should be able to develop a normal starting procedure.
You need to check for an air leak. Do this by spraying some carb cleaner around suspect areas while the bike is running as close to idle as possible. Areas to check are the left side crank seal (under the flywheel- spraying under the flywheel will give an indication if the seal is leaking), the cylinder base gasket and the intake manifold area. If you get an increase in speed with the carb cleaner, you have a leak that needs to be repaired. A good starting place for jetting is back to stock. Your local Honda dealer should be able to give you the stock specs. Once you get the erratic running sorted out, you can fine-tune the jetting for optimum throttle response.
The resistance checks the manual gives are to be taken with a grain of salt. The fact that it runs normally, and as it heats up starts misfiring, tells me the electrical components should be checked in a failed state. In other words, with the components cold, they'll check fine. Besides, even if they check okay at operating temp, that doesn't mean they are okay. Resistance values are meant to be a diagnostic aid but not an absolute test. Even if you get a reading out of specs, that doesn't mean that part is causing the problem. Make sure all the ground points of all the components are clean and free of corrosion (coil mounting tabs, etc).
Are All 250R
What I'm wanting to know is this:
Thanks for any and all help.
I'd check the replacement crank or rod kits (OEM and aftermarket) to see if they are the same. I'm not sure of the ATV's, but the CR cranks are the same for a number of years. This should give a good indication of the interchangeability. If the port timing is different, and that's the only difference, it'll give the power delivery characteristics of that cylinder.
Thanks In Advance
There isn't a heck of a lot that can easily be done to the 50cc racers. Make sure the jetting is as close to optimum as you can get. You can have some porting/compression mods done to get more power but they may sacrifice some reliability and make it even harder to tune.
Get a new dealer. Sounds too much like an air leak to miss this. Is your XR a dual carb model? If so the carb set up is difficult to do correctly and can give a variety of symptoms. These are the two directions I'd pursue.
I would look at the book, but I bought the bike used and it did not come with one...
Any recommendation is appreciated...
A manual is the first thing I'd buy for your bike. It is full of info you'll need. The torque specs for the case screws is 7lb/ft. I'd snug them all up first and then tighten them in a circular pattern. You won't need to go in a criss-cross pattern.
My question is, is there anyone that manufactures just sections of frames that you can buy, or just the whole frame. Would this just be expensive? For what years was the frame made? Any help would be greatly appreciated.
A frame will be almost cost prohibitive for that bike. I'd suggest going to a good welding shop and have them weld in a new tube. It doesn't have to match the exact bend as the original but just strengthen it adequately to be safe. You can even get the original color frame paint from PJ-1 to make it match the rest of the frame.
All the YZ 100's had a bore of 50.00 mm from the factory. Wiseco makes original and oversized pistons for your bike.
I have messed with the front rebound and dampening a little and done the same with the rear. What setting would be best to try on the front and back or should I change out the stock springs and go with a higher rated spring? I weigh about 185 pounds with equipment on. What should I do?
Your KX came with progressive rate springs from the factory. Most guys replaced the springs with straight rate springs first thing. But I don't think that's your problem when you're on trails. If the fork oil hasn't been changed in a while, I'd definitely do that first. Old oil can make the fork action quite harsh. Doing this would be the first place to start to make the forks plusher.
The kicking sensation in the rear could be the shock rebound set too light. I'd start out with the shock rebound adjuster set at 12 out from fully seated lightly. Make sure the rear spring sag is set to 100mm with you standing on the foot pegs, not sitting on the seat. Start out with the fork clickers set at 14 out for the rebound and 12 out with the compression adjuster with fresh oil. Anything that is going to make it better than that will have to involve a substantial investment in springs and possibly a revalve.
I Want To
Your best bet is to ask around at your local bike shop for some events. You can check the printed copy if Cycle News, in the "calendar" section for races listed according to state and date. Generally speaking, a desert race is more difficult to set up and organize than a local motocross since land permits and permissions need to be granted well in advance. There is a much larger support staff that is required to put on a safe desert event. The "Best In The Desert" is a sanctioning body that holds a few quality events a year, some being quite long (500+ miles). Check their website for some details. Try www.bitd.com for more info.
How do you tell how much oil goes in a RM 125 1996.
A veritable cornucopia of information can be found in the original Suzuki owners manual.
Editor's note: Generally Suzuki will cast the oil capacity into the side cover near the kick start, it is usually measured in milliliters. Mark is right though – there are excellent tips and tricks in the OEM manual – order one from your local Suzuki dealer.
It's no secret I'm a fan of the V-Force reeds. They provide a big boost in throttle response from low RPMs all the way to a great top end. Remember to rejet to compensate for any reeds you choose to use, or you may be disappointed or just not realize the full benefits available from the reeds. Cometic makes a gasket kit that comes with a thinner base gasket, this is known as their "high performance" top end gasket kit. The thinner base gasket will raise the compression slightly and lower the port heights giving better low and midrange power. A nice benefit when you do your next top end.
Buying - 1995 Kawasaki KX 125
That is a question I can't answer. I can't imagine a rattle, coming from the top end that doesn't increase with engine RPM. The power valves can make some noise if they are loose or worn, and eventually hit and destroy the piston if not fixed. But even this would most likely follow some pattern that followed engine speed. You're on your own with this one. It might get quite pricey trying to fix this if, or when, it develops into more than a noise.
You need to install a lighting coil. This lives behind the flywheel on the left side of the crankshaft. I'd contact a company who does specialty electrical work like winding coils for that bike. Try looking in the back of a printed issue of Cycle News. They have an ad section with countless ads from aftermarket companies. Look for one called "Ricky Stator". I've heard good things about them and their service.
You can use either the stock CR piston or any one of a couple aftermarket pistons. If you go with an aftermarket piston (and I would), I'd go with the Wiseco. Some of the others are designed to be changed in a very short time span.
Sounds like the clutch isn't releasing fully. This can be caused from anything from transmission oil to a notched clutch basket or hub. The metal plates may also be warped, giving the same symptoms. Use the stock clutch springs instead of the heavy duty springs some people recommend. If the cable is stretching, it can give the same symptoms you have.
With you tipping the scales at 255, you need a pretty big bike. If you get anything smaller than a 250, you're going to have places you need more power. The YZ 250 (two stroke version) is an excellent and versatile bike but would have some fairly harsh suspension in stock condition for woods riding. I think I'd look at a Gas Gas 250 or 300 or a KTM 250 or 300. These are great off-road bikes that have a much more "useable" power output than the 426 you rode. Either 300 would be a great bike you can learn on and not be limited once you get comfortable with it. You'll be able to ride that bike for a long time without worrying about outgrowing it. Gas Gas also makes an excellent off-road bike but there may not be quite as many dealers around for the Gas Gas. One dealer who has outstanding support all over the country is Jim Cook at Smackover Motorsports in Arkansas. He is a rare breed of person and can be trusted to sell you what you need and not what he can make the most money on. He may have a demo or a year old bike for sale. Go to www.smackovermotorsports.com for more info on some excellent bikes.
Sounds like you're on the right track. Check things like the gas cap and carb vent hoses for plugging. These can give some unusual intermittent symptoms. If the float needle is sticking periodically, it can also give some weird symptoms. It may be so work that it is hanging up in the needle seat.
(or Pipe Dream)
Yes, I know how and no, I won't tell you. This is something that can be dangerous at best. The $40 is more than worth it to pay to have it repaired professionally.
The best thing I can recommend for stiction is an oil additive made by Dow Corning called Gear Guard M. This is a moly disulfide oil additive that works extremely well. Adding about 3ccs per leg will do wonders for your stiction.
Oh yeah I took the air cleaner off and tried starting but it wouldn't start. You could tell it wanted too. I honestly don't know if this is related because sometimes it's a bear to start and I honestly don't know when it will start right up or not. Arghhh!!!! Someone help!
If you got enough water into the motor to do any damage, it would have occurred immediately. If there is any remaining, it may corrode so don't' delay in getting it started again. First thing I'd do is pull the carb apart and clean its internals thoroughly. You might have some water in an electrical connection but they are normally fairly resistant to water.
I have a 1994 RM250 that I am rebuilding. Are aftermarket crank/ rod assemblies worth the money, or is the stock assembly good enough? There is nothing wrong with my crank/rod/bearing assembly, but would the aftermarket bottom end make a noticeable difference in performance/durability? I am a novice and never race the bike; I just use it for a trail/play bike. And could you recommend a good piston manufacturer, or is OEM just fine? And I need a flywheel puller, could you recommend a quality tool company, Snap-On does not make one for my bike.
Thank You - Leo
The aftermarket rod kits are a good quality if installed correctly. If you don't use a stock RM piston, I'd recommend a Wiseco piston kit. The rod kit won't give any increase in power or reliability except from the standpoint that it is new and your existing rod isn't. If you have no perceptible up and down play in your lower end rod bearing, it should be fine for a while. There is also a side clearance you can check to measure the thrust washer wear. Check your manual for exact specs.
Motion Pro makes good quality tools for a decent price. They'll have your flywheel puller at a fraction of the price that Snap-On would if they did make one. Check with your bike dealer for Motion Pro tools.
I ran into this exact symptom once with a '96 YZ 250. The thing that fixed the problem was cleaning the coil mounting tabs on the frame. There was paint under the tabs and the coil eventually lost sufficient ground through the bolt threads. It definitely sounds like an electrical problem.
The high dollar plugs aren't helping any, either. I'd use a BR8ES. The 9-heat range plug is one heat range too cold. Stick with the 8 series plug.
Check with Berg Racing for your automatic clutch.
Thank you very much
The X model was their latest and greatest race bike at that time. The fork design was pretty cutting edge at the time as far as the design and theory. I don't know if anyone back then actually knew how to properly set them up (short of the factory mechanics). I'd love to get my hands on a set to see what kind of results I could come up with. I'm not sure of any other differences. The YZ's had huge reed cages in that era, but they were all the same size for a number of years after that also. So I don't think the motor was much different than the early '76 125. Not a bad bike at all. Those things really ran well for a 125.
Thanks - David
Another 2 ounces of flywheel weight isn't going to make much difference. The Gnarly pipe isn't going to tame it down any either. Going up one tooth on the front sprocket will spread out the gearing substantially.
Concerning the low RPM blubbering. No reeds will cure that. That is strictly a jetting issue. Going to a leaner pilot jet will help immeasurably. Porting to tame the power will be the biggest single thing you can do to help make the power more manageable. You can stack up two base gaskets, and this will help mellow it out a bit but porting is the best alternative. Eric Gorr is a wizard with those. Go to www.eric-gorr.com for more info.
Crashed And It Won't Start Up
Sounds like the exhaust is plugged. The noise coming out if the intake certainly isn't right. You may have a damaged reed but it would be a coincidence that it occurred with the wreck. You might try to crank it without the silencer just to see if it starts.
New Top End -
The carb has been cleaned and seems to be functioning correct, and is stock. Please help.
Trevor in MI
I know it seems obvious but have you checked the air filter lately? Either that or the float level in the carb may be too high.
Any suggestions would be greatly appreciated.
Thanks Aaron - St. Johnsbury VT
Vertex pistons are intended to be changed at a very short interval. I think I'd go back with either a Wiseco or a Honda piston and rings. Obviously, check for the air filter to be torn again or not sealing correctly. Check the intake boot between the filter and the carb for signs of dirt. It should be 100% clean. While you have the top end apart, I'd measure the bore to make sure it isn't too large. Excessive clearance can accelerate wear substantially.
Thanks for reading this. Dave Z.
Believe it or not, a "one kick cold" starting bike is jetted too rich on the low speed circuits. If you can get it to start on one kick, I don't think I'd complain, or take any actions to cure it. The difference in compression from the old motor to the new can cause the difference you have. Your motor is not running too cool due to the water wetter and anti-freeze. Even if it were, it wouldn't affect the starting. You can use tap water without doing any damage to your motor. It will run cooler with a 50/50 mix of coolant and water than it will with straight coolant.
There are too many variables to give you exact jet numbers for his bike. The altitude and temp helps but the humidity even has a substantial effect. I don't keep specific jet numbers. Your best bet (or his) would be to jet for your specific conditions. Find a good jetting guide and use it. Eric Gorr has a good one on his site. Go to www.eric-gorr.com for the guide. Chances are he'll end up going leaner with the pilot jet to clean up the low speed jetting. The main jet doesn't come into play until about ? throttle openings and up.
Tyler - Ontario, Canada.
A lot depends on what type of riding you plan on doing. If you are going to be riding trails and woods mostly, a bike designed for that will be your best bet. Whether it is a two stroke or a four stroke is entirely up to your preference. You can get a good two stroke 250 woods bike and it should have a very good useable power output. An XR 250 is a more than adequate woods bike but isn't quite as fast as a KTM 250 EXC. A two stroke 250 will have substantially more horsepower than a 250 four stroke. An XR 400 is a popular bike but is somewhat limited by its weight and suspension. Any of the Japanese 250 motocross bikes can be made to work well in the woods also. If you look at KTMs, I'd stick with a '95 or newer. The suspension made a good improvement in '95 and the motors are relatively durable. At 190 lbs, you could ride a 125 but a 250 would suit you better.
You'll need to lean the jetting to compensate for the altitude. The best thing to do is call a Honda dealer in the area you'll be riding and ask what jetting they normally run in the area. They can give you the most accurate info for riding at those altitudes. You can also check some of the discussion boards that are somewhat specific to your bike. Thumper Talk has some good info. Go to www.thumpertalk.com and visit the XR 650 forum. Someone there may be able to give you good info.
I am looking for big bore kit for 125cc MX bikes
A 2mm or a 4mm overbore have proven to be fairly reliable. Anything bigger than that can vibrate a lot and be less durable than a stock motor. Check with Eric Gorr for the rundown on what your options are. Go to www.eric-gorr.com for the lowdown.
No, it most certainly isn't supposed to shift like that. The in and out play of the shifter is not normal. The shifter is only engaging with the shift drum mechanism when it is pushed in. Some shifters have a white nylon piece that helps hold it in place. If this piece is missing or damaged, it can give the exact symptoms you have. You need to get a shop manual. This should give you all the necessary info you need to inspect the business end of the shifter shaft.
It may not be a jetting issue. You may have an ignition problem, especially with a 10-year-old bike. I'd look very closely at the coil wire and the plug cap. You can buy an aftermarket wire and cap for a relatively cheap price (cheaper than a new coil and wire assembly from Suzuki). Also, make sure the ignition components are grounded properly. The coil can develop corrosion under its mounting tabs and give some unusual symptoms.
There is normally some play in the power valve assembly, especially with the KXs. There are a lot of pieces in the KX valve and there is play between each piece. A routine top end may not address this amount of normal play. There are aluminum teeth that can wear and cause an abnormal amount of play. These parts need to be replaced before the teeth wear down enough to break off completely. But this normally doesn't give a "clicking" sound.
Does the sound come and go when you pull in the clutch lever? Some play in the primary drive gears can make some noise.
I've seen some RM 250s that have a burr on a part of the shift drum mechanism. This burr can prevent the shift drum to rotate fully and engage the selected gear completely. Right at the end of the shift drum, there is a pin about 8mm in diameter on which the shifter linkage rotates. This pin can get a burr or trash between it and the piece that turns on it. This needs to be cleaned or removed before normal shifting can occur. This can be done by removing the right side cover and the clutch assembly with the motor in the bike.
A float needle and seat may appear to work normally but still let some fuel leak through over a period of time. First of all, make sure you're turning the fuel off at the petcock when shutting off your bike for any length of time. Even with the petcock shut off, it still may be seeping some fuel into the carb. You should be able to pull the fuel line and check for any seepage. You may end up having to replace the petcock and the float needle and seat to cure your problem.
Fork Oil, Loc-Tite, & Factory Mechanics
Suspension fluids are measured in a couple different methods. One manufacturers 5wt oil may not be close to another's 5wt oil. The most accurate scale is the one that lists oils in a fraction. Spectro lists an 85/150 and a 125/150. This is much more accurate of an indicator of actual viscosity than the 5wt, 7.5wt, 10wt, etc scale. Personally, I've had excellent results with the Bel-Ray HV1 fluids. I know their 5wt oil isn't as thick as some others. I know its characteristics and will continue to use it until I have good reason to change. Personally, I stay away from high priced synthetic fluids. Their big marketing ploy is that the synthetic fluid lasts longer before breaking down at a molecular level. You should change the fluid long before that occurs due to contamination anyways.
Loc-Tite is used in places where a fastener isn't frequently removed, like an air box or other body plastic fastener. Anti-seize is used in places where a bolt is frequently moved, like a chain adjuster bolt. Anti-seize can also be used in places where dissimilar metals electrolysis occurs, such as a cylinder locating dowel pin.
Concerning a factory mechanics credentials or qualifications. That varies from one mechanic to another. Getting a job as a factory wrench can be as much political as much as anything else as long as you're relatively qualified. It's the old being in the right place at the right time thing. Personally, I use Channellocks rather than a chisel or punch to adjust the steering stem nut. You shouldn't have to re-adjust it between re-greasing the bearings. So, I adjust it when I'm reassembling everything the first time. I do use a punch for the shock spring preload adjuster locknut. You'll find advice that you find unusual from a lot of sources. Keep an open mind and try to find out why someone does something one way rather than another. I continually hear of different ways of doing things. If it is better in some way, I may start doing it that way. Just because they call themselves a "factory mechanic" doesn't mean it is the way you should do it.
Okay, we'll go down the list?.
Make sure the throttle tube is in good condition (not cracked, etc) and that the end of the tube/grip isn't rubbing on the end of the handlebar. I don't use any lube on the end of the handlebar since it can attract dirt. Also check the carb slide for dirt or flaking of the chrome plating. Check the roller at the throttle assembly to make sure the cable isn't getting wedged between it and the housing. Yamaha has a recall on the '96 and newer YZ two strokes for this problem. The RM throttle is very similar and could do the same thing. The only other thing I can think of is if the cable is getting pinched somewhere such as the steering stops.
My problem is that the float bowl is out of adjustment, over-flowing fuel. However, the pin to remove the float, which is usually loosely set in, is in this case pressed in. This is very strange. I tried tapping it out, but didn't want to damage it. Is tapping it out the way to go here? Or drilling it out, which of course, would ruin the pin. Thanks for any info.
It may only be able to be pushed/tapped out in one direction. Using a small punch, tap in one direction. If it doesn't go, try the other direction. Obviously be very careful since you don't want to break the cast towers the pin pushed in to. I don't think the adjustment is causing the fuel to overflow. It is probably a faulty float needle and seat.
Tips For Winter Riding?
I'll do motocrossing, play around a bit in the woods, and go flat-out on frozen lakes.
My bike is a RM 250 '98, stock except Boyesen Pro Series reeds, Ohlins shock. At 158 - 2nd - 42 my jetting is two steps leaner on the main, one step leaner on needle and pilot, as compared to stock. I run a NGK B8ES or equivalent Bosch plug, and standard 13/50 gearing. Castrol TTS or equivalent fully synthetic at 3 % in EURO Green (unleaded) 95 octane with 5 % ethanol (the standard pump gas around here). Trans oil is Castrol "dirtbike trans oil". (It's red, anyway... And a bit expensive.)
This all seems to work fine now at around 10 C. Last winter my RM 125 seemed all right, but you don't learn from not asking... Any suggestions?
The only things you should have to worry about for extreme cold weather is your jetting and possibly the engine not reaching adequate operating temp since there is no thermostat for the cooling system. The colder temps will lean the fuel/air mixture enough that you could do engine damage if you don't compensate for it, especially the main jet. KTMs come with a thermostat for the cooling system. You may be able to adapt one for your Suzuki to help control the engine-operating temp. An engine that isn't at operating temp stands a chance of premature wear at an alarming rate.
Back In The
I will be mostly riding in the Ocotillo Wells area. What modifications if any would be best suited for my new (to me) scoot? I'm 5'9" 170 lbs and used to race Expert/Pro class.
Any help is appreciated!
Your 500 in stock condition will work quite well. Do normal set up like setting the rear spring sag for your weight and clean up the low speed jetting and you should be quite happy with it as it is. You may find the forks to be a bit on the harsh side. In this case, making sure the fork oil is fresh may help a little but you'll probably be much happier getting them revalved by someone like Precision Concepts.
Buy - XR200
Thanks, I really appreciate it. Eric
An XR 200 is a great bike for it's intended purpose, and that is an easy to ride trail bike. As long as you don't try to go too fast with it, or try to make it do things it wasn't intended (like jumping), you'll get many years of enjoyment out of an XR 200.
Absolutely, you'll probably end up at around a 48 pilot. It's amazing what a $5 piece of brass can do for the running quality of a bike.
You should be able to install a hot start kit for almost any bike on your DR. The kit for a KLX 300 has a fitting that is installed in the intake manifold and would be installed the exact same way on your DR. Yes; the hot start is simply a filtered air leak around the carb that leans the mixture temporarily for easier starting. Check with Thumper Racing.
I'm not a big fan of octane booster, especially on a stock motor. It just isn't necessary. The benefit of running a race fuel with a stock motor is the consistency you get with race fuel out of a drum. You may have the idle speed set too high. That can have a substantial effect on low to mid jetting. The pinging you're hearing is dead giveaway. Make sure the slide stop screw isn't raising the slide too much and turn the idle down as far as you can stand it. This is the first place to start.
I Need A
Signed, "I need a plug"..... : )
Two things will help. One is running a BR7ES spark plug. The other is leaning the low speed jetting. The pilot circuit is mainly the culprit when you get plug-fouling spooge like you're experiencing. I'd repack the silencer before beginning any rejetting. Make sure the core holes are clear and unobstructed and don't' pack the new packing too tightly.
Miss - RM 80
Thanks - John.
I'd take a close look at the reed petals. If they aren't sealing adequately, it can give some symptoms similar to what you're having. Also, make sure the silencer packing is fresh. Corrosion around electrical component connections can give some erratic symptoms also. Check the coil mounting tabs for rust or corrosion.
I've never seen a set of cases crack in that area. Not saying it isn't possible, just that I have never seen it. I've seen what appear to be cracks that really are casting flaws. If there were cracks, your 500 would be shaking itself apart in very short order. Since you have no symptoms, I'd reassemble it and not worry about it until some problem appears.
Is my problem electrical, i.e...stator or should I point my search elsewhere??
Thanks - Dave
The fact that it won't run with the recommended resistor plug leads to an electrical problem. The fact that it won't start with the electric starter leads me to believe you have a voltage drop somewhere. I'd check the source voltage to the ignition system at different points. Check it with the battery power only and then with a battery charger hooked up, or even jumper cables hooked to a car. If you're not getting battery voltage to the ignition components, then you have a voltage drop due to a poor connection of corrosion. Check for corrosion at all electrical connections and ground points. This includes places where components are mounted, such as the coil mounting tabs.
Many Thanks - Phil
I know some of the Kawasakis had to have the cases split to gain access to the crank seals. I'm not sure about your KX. I don't think you have to but I may be wrong. You can remove the right side cover, the clutch assembly and the primary drive gear on the end of the crank. The seal is directly under that gear.
Second question, if I just want to replace the shock bumper only, The first step is to release all the nitrogen gas out of the shock, Second, release the clevis end nut, put in the new bumper, screw back the clevis end . Recharge the air set at 150 PSI into the reservoir right?
Thank you, Douglas
The size of the reservoir has nothing to do with the capacity it has to hold pressure. The tank I charge shocks out of is only about twice the size of your portable air tank yet it is charged to 2000 PSI. The thickness of the walls of the container are what determine how much pressure it can hold. The stock shock on some of the Honda XRs hold 285 PSI. As long as the circlips is seated in it's groove correctly, you won't have a thing to worry about.
Replacing the shock bumper only can be done the way you describe. It may be a little difficult to get the locknut off the shock shaft since it can be difficult holding the shaft from turning without damaging it.
Any suggestions? I am also looking for a way to lower the seat height but I can't find a smaller seat anywhere.
Thanx for your time
The swing arm bearings can get stiff during times of sitting if they are dry. That would be the first thing I'd check. You may consider cutting the existing seat foam with a bread knife. But this will result in a harder seat. You might consider having the suspension lowered. This is the most expensive way to go about it but by far the best way. This involves installing spacers in the forks and shock and using springs that are not only shorter but also the correct rate for your weight. It isn't cheap but would help your riding more than you'd ever imagine. Go to www.mx-tech.com for some info on lowering your bike. Ask for Jeremy and tell him MX Tuner sent you.
Also, I haven't gone to Whisenhunt yet, because I'm not sure if my boys can handle it.....no-one seems to give me a straight answer (they are 10 and 12, and all we do is trail ride and small jumps, nothing wicked) anyways, thanks in advance, Jon
Your owners manual should give most of the info you need. If not, Yamaha offers a shop manual that will go through the entire bike, from one end to the other. This will go over checking and/or servicing the fork oil. This will include any special tools needed.
Whisenhunt is not a difficult area. They show the trail difficulty on a map in the parking area. And if you encounter a trail that becomes too difficult, you can turn around and return the way you came. The central trail is a road large enough for a jeep to drive down. There are some difficult trails but they are marked "most difficult".
Thanks for your time and help.
Steve - Atlanta, GA
Sounds like you have a plugged passage in the carb. Probably a plugged pilot jet. Try cleaning the carb with some aerosol carb cleaner. Be sure to blow through the passages to verify they are clear.
Thanks - Aaron
If you're running at wide-open RPMs nearly 100% of the time, I'd run a BR9ES. Otherwise, use a BR8ES. Don't bother with the high dollar plugs. They are a waste of money.
By fuel mixture, I'm assuming you mean the fuel/oil mixture. Your CR will do quite nicely run at a ration of 40:1.
I have two questions:
The head for the '86 KX won't interchange with the '91 head.
The biggest improvement you can do for an XR 400 is to get the suspension fixed. The spring rates are unbalanced from the factory. The fork springs are too soft for anyone over 150 lbs and the shock spring is too stiff for anyone under 210 lbs. Getting the spring rates closer to what you need will help a lot. Race Tech sells a compression adjuster assembly with Gold Valves that increases adjustability, improves plushness and bottoming resistance. The improvements are dramatic. By far the best money you can spend on that bike.
---thanks in advance
I can't give you exact jet numbers. Your best bet is to rejet according to your local conditions for the best throttle response. Eric Gorr has an excellent jetting guide on his website. Go to www.eric-gorr.com for more info. You'll need to go leaner to compensate for the V-Force reed cage. You'll be quite impressed with the motor once you get the jetting sorted. Those reeds are great!
Is the rear brake pedal feel soft or stiff? If it is soft, the master cylinder isn't generating proper pressure against the brake rotor. Bleeding the brakes may help eliminate this problem if there is air in the system. If it is stiff, the caliper piston or sliding pins may be binding so the pads aren't applying the pressure against the brake rotor. This will require finding the parts that aren't moving freely and cleaning and lubrication them.