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.

Hare Scrambler
Hi Mark, Can you help with any info on pre-loading the power valve so it slams all the way closed and stays closed longer for crisper bottom end? I read about this mod on Ty Davis KXs. I need to know how to do it to mine. We need all the low end we can get.

Thanks,
Alex 97 KX 250. Missouri State Hare Scramble racer 250 C & B

I'm not familiar with any mods to the power valve to help keep it shut longer. Normally, it doesn't open until about half throttle anyways. Usually by that point, most riders are looking for all the power they can muster out of their motor.

One proven option is a V-Force reed cage. Installing this and rejetting (you'll need to lean out the jetting across the rev range) will give a major boost in low end. The key is to jet the pilot circuit as lean as you can. This will give you some eye-opening throttle response.

The cage comes with an adjustable reed stop. Make sure to set it in the low-tension setting.

A flywheel weight can help get things going in poor traction situations. A 10 oz weight can work wonders.

MX Tuner

Don't Laugh!
...but I have a 1985 Honda CR250R that I bought in non-running condition several years back. At the time I bought it, both the bottom and top-end had been newly rebuilt but the electronic ignition was bad. I finally put it back together and it has plenty of power but runs very rich. I would like to find an article on the 1985 CR250R that gave the hot tips on setting it up (suspension, jetting, etc.). I realize that was a long time ago, do you have any suggestions on finding this type of information?
Also, is there an aftermarket company that specializes in parts and accessories for older bikes?
Any help you can give is greatly appreciated.

Thanks, Les

You might try contacting some of the magazines to see if they still have back issues for your bike. Don't get your hopes up about bike set up tips, though. Even today, they miss the mark pretty significantly with bike set up numbers. Your best bet is to fix what is wrong with your bike. If you find a trait that is undesirable, address that issue. Jetting for instance. You're better off simply correcting the jetting yourself. There are some good on-line jetting guides. Go to www.eric-gorr.com for one of the better ones.

Concerning your suspension, the first thing to do is have the existing components serviced properly. The fork internals need to be disassembled and thoroughly cleaned and filled with the proper amount of the correct fluid. Then, and only then can you get an accurate assessment of what the bike really needs.

MX Tuner

Slow CR?
Dear Mark, I have a 1983 Honda CR 250. The problem I'm having is a lack of top end horsepower; it doesn't want to rev on up. The bike has low-end power, but seems to running rough at that. It had a collapsed barrel gasket, I replaced it and I also installed new Boyesen reed valves. I recently went through the carburetor but didn't find any problems. What size jet would you recommend for the carb? Also, I'm not so sure if the bike has the original black box (between the magneto and coil). Is there a way you can send me a wiring schematic? I noticed there are a couple of wires that aren't connected. I appreciate your time and look forward to your reply. If you need more info on the bike please let me know.

Matt

A service manual would be a good place to start for some info. You should be able to find a wiring diagram in a decent manual as well as stock jetting specs. The stock jetting may not be perfect but it should run acceptably and certainly run strong at high RPMs. I'd check the timing and even check to see if the timing is advancing by using a timing light.

Is the exhaust restricted at all? That could make it run poorly at high RPMs.

MX Tuner

UNI-TRAC Not Adjusting
We've got an '85 KX 125 bought last year used. Rear UNI TRAC shock dampening will not respond to adjustments. Oil residue was all over the bottom half of the shock and my guess is that it has had a bad seal for some time, all oil has leaked out and here we sit. My question is how difficult is it to rebuild the shock? How expensive of a job is it also (seals, special tools etc.) We aren't expert mechanics but have enough savvy to have successfully installed new front fork seals. Should we look for an after market unit instead?

Thanks, Bill

No, a decent suspension shop should be able to rebuild your stock shock for less than $150, parts included. The fact it has leaked out a lot of oil might raise some concern, though. If the shock is run low on oil for any amount of time, it can quickly damage some of the internal parts. The shaft or the inside of the shock body can wear to the point of needing repair. The shaft can be re-chromed if it isn't worn too far and the body can be re-anodized but both of these can add $100 each to the price of the rebuild.

I doubt if you'd be able to locate an aftermarket shock for your bike. If so, chances are it would cost more than getting your shock repaired.

Whether you can rebuild it is something I can't answer. I've had to repair shocks that had just been "fixed" by someone else who thought they could rebuild shocks. It isn't rocket science but it can be tricky if you don't know what to watch for. It can create a very unsafe riding condition if it isn't done right. This isn't something that should be learned alone. It is far better to have someone show you how to do it. I'd be glad to show you if you're in the Atlanta area.

MX Tuner

MX100, Yamaha, 1979
I have a problem with my front suspension. It only compresses about an inch and that's it. Nothings bent or there's no visible damage I can see from the outside. It does not leak oil or anything. Is it just worn out or is there too much oil in them. The shocks have never been opened since leaving the factory well that's what the guy said who I bought it off. If I have to replace the shock oil what should I use, I herd that you could use automatic transmission fluid. I've never took a shock apart so this is fairly new to me, it also my first dirt bike. Any help will be appreciated.

A shop manual will give you all the necessary info you need to rebuild your forks. It sounds like someone may have filled them full of oil.

MX Tuner

Oil Ratio for '70s Kawasaki
Hello, I have a 1970 Kawasaki 175 2 stroke bike. I was wondering if you could help me get info on gas mixture for it. I'm not sure how much to mix together. It had a tank that you fill with oil and it mixed itself with the gas in the motor, but the tank was gone when I got it and they mixed the gas in the tank. If I could get some help on the gas mixture ratio that would be great.

Thank you, Charles

Your 175 will do fine on a mixture of 32:1. That should be 4 ounces of oil to each gallon of gas. Stay away from castor based oils. Semi-synthetic oils would do great for your bike - Yamalube 2R, Honda HP2, or Golden Spectro.

MX Tuner

Killer Clutch Pull
Hello, I have a 2000 CR 250 with a clutch that I can pull in for about 15 min. of riding on a motocross track. After that, my finger feels like it's going to fall off. It wasn't that bad when I bought the bike, but now it's really bad. I also installed an Easy-Clutch which helps some. I replaced the plates and springs and filed down the basket (which wasn't in to bad of shape). When I go into a turn and pull the clutch in, it doesn't disengage all the way so it stalls. When I pull it in with my finger (with my gloves on) it won't disengage all the way either. The only way it will is if I pull it in all the way to the grip, or if I adjust it so tight that there is no play at all in the lever, which makes it even harder to pull in. I'm 45 yrs. old and my racing days are limited.

What do you think? Thanks

I think you're too old for this stuff. Take up something safe like golf. Relax...

I'm kidding. You only have two years on me.

Sounds like the clutch cable is dry, worn, and frayed. First thing to do is install a new clutch cable. While you're at the bike shop, pick up a cable pressure luber. This is a little gizmo that fastens around the loose end of the cable and injects your favorite lube down the entire cable. Keep squirting until you get lube out the opposite end. I've tried everything under the sun and the two best lubes I've found are either WD 40 or Tri-Flow. Tri-Flow can be found at Wal-Mart stores in the sporting goods department. Tri-Flow is basically WD 40 with Teflon in it - good stuff for cables.

The next tip may seem insignificant but it works and works great. When you install the new cable (or even when you're lubing an old one) put a blob of clean grease in the hole in the lever where the barrel end of the cable goes. If the cable end has a metal sheath over the lead barrel end, try to get some grease in between the sheath and the cable end. The whole point is that the barrel end needs to slide/rotate as you pull the clutch lever. It needs to be lubricated with grease. Same with the lever pivot bolt and hole. Lube is good.

If you still have stiff clutch pull, someone has installed a set of aftermarket (Barnett, etc) clutch springs. You should use stock CR springs. These are the best you can buy for your CR. You shouldn't need an Easy-Clutch for your bike. The Easy-Clutch is a band-aid fix for other problems.

MX Tuner

Blown XR200
Hi, I own a 1985 XR200 it doesn't have any aftermarket parts, all that has been done to it is that the baffle has been taken out of the exhaust pipe. The problem that I have had is that I was riding yesterday and I went to accelerate and then it went kaboom! I saw that just behind the skid plate a fair size of the engine casing had separated from the rest of the engine, it had lots of oil in the bike and I wasn't riding it exceptionally hard. I bought the bike for $1350 Canadian and now I would like to know if it is worth it to fix the engine, or if I should buy a new one. At the motorbike dealers near me they have givin me no attention because I am just 15. Also, I would like to know what a new XR200 and an XR400 engine would cost, and if I can even fit the XR400 into my bike.
Thank you
Matt

I hate hearing about stories like this. The only thing that will bolt in place of the stock XR 200 engine is another XR 200 engine. The engine cases are going to cost a couple hundred dollars minimum. And they may only come as a matched set. That won't include any of the bearings, seals or gaskets you need not to mention a lot of labor involved in replacing the cases. You're most likely going to come out cheaper trying to find a used engine. The only problem there is you have no idea how that motor was treated in its previous life. It can be a big gamble.

MX Tuner

High Maintainance
Hey, I was just wondering if all 2-stroke dirt bikes are high maintenance bikes. I'm 15 and I have had a Yamaha RT 100 for about 3 years. I think it is time for a new bike and I was looking at a Kawasaki KX 100, I was looking at the KX 85 but I'm a little big for it and my father doesn't want to bye a 125 for me, so the only one left is the 100. Well any ways my father thinks that because it's a 2-stroke motocross it is high maintenance. I'm not going to be racing so I don't it will be that high of maintenance but I have to know before I buy. So if u don't mind could you tell me if it is high maintenance and if it is could your suggest a better, and lower maintenance bike

The recommended service intervals listed in the service manual are for a bike that is raced continually. That means hard, high rpm running. Recreational use is much easier on all internal motor parts. But accumulated time is still running time on a motor and its internal parts. So basically the KX 100 will be a higher maintenance bike than your RT 100 but should still be an acceptable bike for you to ride. It may need to have the top end done (piston and rings replaced) once a year to prevent any internal engine damage from occurring. Chain and sprocket wear should be similar to your RT. Clutch life is determined by your riding habits and should remain about the same as with your RT. Air filter maintenance should be done before every ride, just like your RT. You are cleaning your air filter before every ride, aren't you?

MX Tuner

Power to the TTR!
My boys have a TTR125 and a TTR125L, and I have a TTR225. Everywhere I read something about these bikes, they say they are modifying the airbox in order to gain power/speed. Does it really make THAT much of a difference, and if so, is there anything that will be damaged in the long run by doing this?

Jonathan

Seeing where you're from, I'm guessing you ride at Whisenhunt? I ride there a few times a year myself.

Some bikes have an airbox that could be restrictive at higher RPMs, when maximum airflow into the motor is needed. The only time modifying the airbox would be beneficial is in higher rpm conditions. Some air box mods might make the bike less tolerable of wet riding conditions, so be careful of what you attempt. Cutting holes is easy. Plugging them adequately may not be so easy.

MX Tuner

V-Force ou RAD-Valve
Hi Mark, I have a Honda 250 CR 2001, and I wonder whether it would be a good idea to buy a V-force power reed to increase the bottom power of the bike. Do you think the V-force would be better than the Boyesen RAD-Valve? Is there any other way to increase the power of the bike?

Best regards, Christophe
France

It's no secret that I'm a big fan of the V-Force reed cage. I was a Boyesen advocate for a long time. But there just isn't any denying the fact nothing works better than a V-Force reed system.

Another cheap and relatively easy mod that works well is raising the compression slightly. Cometic makes a top-end gasket kit with a thinner base gasket. This does two things. One is brings the cylinder and head down just enough to boost the compression a bit. The other benefit of a thinner base gasket is it lowers the effective port heights in the cylinder. This also works to give the motor a substantial boost in lower RPM power.

Other than that, the sky is the limit as far as motor mods are concerned. Just like in drag racing, the magic question centers around how much money you want to spend. Just how fast do you want to go?

Tuner De MX

Qu? A?o es mi IT 465?
Hello, my name is Alessandro and I am writing you from Mexico City.

I've just discovered your site and I wish to express my congratulations! I was wondering if you could possibly give me some clues on a motorcycle I've just got from a friend:

It is a Yamaha 465 IT, whose former owner seems to be unable to tell me the model year of the motorcycle, because the original papers got lost in a fire (all we have now is some sort of legal certificate of property)! All I can tell you, is that it is blue with yellow stripes, and it does carry a head and a tail lamp...

I was wondering if you could possibly help me gather any information on this machine: when was it produced? (In the eighties, I presume...) How many h.p. does it deliver? How much does it weigh? Maximum speed? How can I determine the year of production? (the dealer says the serial number is not enough; how peculiar...).

Sincerely, Alessandro
Mexico City

The IT 465 was only made two years, in 1981 and 1982. I think the blue started in 1982, but I may be mistaken. It is essentially the same bike between the two years, so ordering parts shouldn't be a problem.

I really don't have any specifics on the bike itself. I'm guessing it produced in the range of at least 35 to 40 horsepower and should certainly do about 80 mph if geared correctly.

Your dealer should be able to tell you the exact year with the frame serial number.

Sintonizador Del MX

I Need a New Foot!
I need help, I have a problem with my 1997 KTM 360sx its been running fine but the other weekend it became very hard to start that hard in fact it took the skin off the bottom of my foot. It eventually fires but as soon as I stop it or I stall it - it takes ages to start. It has always been bad to start but that's ridicules. I'm not a small person and have plenty of power to kick the bike over I've tried the usual check the plug fuel air etc and its got all of them so I can see the problem because as soon as it fires it runs sweet. I need help because its playing havoc with my foot I'm struggling to walk after the last time I was out on it.

Thanks in advance

Joe

A couple things to check come to mind right away.

• I'd check the carb for trash.
• Make sure the float level is correct and that the float needle is working correctly.
• Do you have fuel dripping out the over flow hoses?
• Inspect the reeds. If they are beginning to chip or fray, they can give symptoms similar to what you're experiencing.
• You may have some corrosion in an electrical connector giving your problem.
  • Pull apart all the electrical connectors and look for anything but a nice clean connector.
  • If it isn't clean and dry, spray some aerosol brake cleaner or electrical cleaner in the ends of the plugs to remove the contaminants.
  • You may even need a wire brush in a severe instance.
  • Don't overlook ground points for the electrical system. These include the frame tabs the ignition coil mounts too.
  • Remove the coil and sand or wire brush the tabs until you have bare metal.
  • Now use a dab of clean grease to coat the mounting points before reinstalling the coil.
• Check the spark plug wire and cap. If they develop excessive resistance, they can give a variety of problems.

MX Tuner

Kickin KX
Hello All, I have a question my KX is hard to start after the first kicks from cold. I have looked in the stator and there is only one coil I am sure there should be two.

If we push the bike in a high gear and let out the clutch, the bike fires up fine and runs well. But it won't go with the kick-start.

I would like to know if you think this is my problem.

Thanks Chris K "UK"

I'm going to venture a guess and say your KX only came with one coil attached to the stator. Not knowing what year KX we're working on doesn't help much. I think I'd check some of the basics before I'd be blaming ignition components. Check the carb. Is the float height set correctly? One trick that may be of help is leaning the bike over on its side until fuel drips out the overflow hoses. This richens the mixture initially and has helped more than a few riders crank their bikes cold. Make sure the reeds are in good condition. Has anyone been swapping jets in the carb? If it is too lean in the pilot circuit, it may be difficult to start cold.

MX Tuner

The Warmup...
My Macho son thinks he needs to warm up his CR 250 for over 5 minutes. I say he just as well get on the son-of-a-bitch and ride it rather than making the rest of us listen to it. I own two dirt bikes myself and am not anti-dirt bike. Please let us know if one needs to subject the rest of the family the incessant drone of him and his four friends CRs in our front yard.

Thank You.

Graydon

No, Graydon, you are absolutely correct. The best way to warm up a bike is to ride it without putting the motor under a hard load. In other words, riding it will warm it up better than anything else. Once it starts, he can put it in gear and pull away.

MX Tuner

What Oil?
I have a 1998 XR200R and I don't know what kind of oil to put in it. Or what weight of oil to use
Can you help me?

Adam

Your owner's manual will have very specific recommendations concerning oils that are approved to use in your XR. Generally speaking, the motorcycle manufacturers list automotive oil specifications that need to be met. In other words, you can use regular automotive oils in your motorcycle without concern of doing any damage as long as their oil change intervals are followed and you use an oil that meets Hondas recommendations. I believe an SH rated oil is what Honda calls for. The viscosity will vary depending on your local air temperatures.

I know it is considered sacrilege by some to even contemplate using anything but the high dollar motorcycle specific oils, but it just isn't necessary. Changing your oil frequently will help extend the life of your motor, regardless of which oil you choose.

MX Tuner

Bogging KX
I just purchased a 1993 Kawasaki KX 125. The seller told me it had a rebuilt top and bottom end and still wasn't broken in yet. The bike appears to be in very good condition for the year and it came with an FMF gold series pipe.

When I ride the bike it will only accelerate well at 1/4 throttle, any more and there is a big bog. Even revving it in neutral causes a bog and allot of smoke. I pulled the plug (br8es) and it was black but not wet. The gap was only about .020. I opened the gap to .030 and I think it ran a little better. I also noticed black fluid (oil?) coming from the exhaust. The kid told me to only turn the fuel petcock on 1/4 of the way because it had a JET in it. I am assuming without pulling the carb yet that maybe it is jetted wrong for the pipe or they put in different jets without knowing what they were doing. I just got the bike several hours ago so I don't have a repair manual yet, the nearest shop is far away so I have to order it thru the mail.

• What spark plug should I use and what gap?
• What gas oil mixture?
  
• What type of oil do I use in the crankcase?
  
• What do you think is causing the bogging problem?
  
• There is also no lid on the airbox, is there supposed to be one there? If so, do I have to have it?
  
• If the engine is new, how should I break it in?

Thanks in advance for any help you can provide.

Sounds like you're right about it being too rich. The kid is fairly clueless about jetting. Virtually all bikes with a carburetor have jets. A jet is a fixed orifice that can be changed to alter the fuel/air mixture. Different jets control different circuits determined by the throttle opening. Sounds like he went way too rich with the main jet. Your KX came with what is the equivalent to a B9 series plug. The BR8ES you have in it is probably the best for what you'll be doing with the bike. A fuel/oil ratio of 40:1 will be what you need to start with. You should be fine with that unless you run at extended full throttle RPMs (desert riding, etc). Choose a synthetic or a semi-synthetic but stay away from castor based oils unless you plan on tearing your motor down once a month to remove the build up that will accumulate. Yamalube 2R, Honda HP2 and Golden Spectro are a couple popular choices that are readily available.

For the gearbox, Kawasaki lists an automotive oil specification. You can use an automotive oil, a motorcycle specific gear lube, or even Type F automatic transmission fluid. Regardless what you use, you're better off changing it very frequently. Type F ATF works great and is about the cheapest thing to use. You'll get very good clutch actuation with it. Plus it protects very well against wear. The same components that are in your gearbox are in an automatic transmission (gears and wet clutches).

As long as the motor has been run a couple times and cooled off completely, it can be run normally. There is very little required break in time for your engine as long as it was assembled correctly.

Don't worry about the top for the air box. If there was one available with the bike when it was new, it was only intended for extreme wet weather riding.

Your jetting is the first thing that needs to be checked concerning the bogging you're experiencing. I'd go back to 100% stock jetting for a good starting point. Chances are you'll need to go leaner with the pilot jet and maybe even the main jet a step or two. Start with the pilot jet and then fine-tune the throttle response with the needle position. It wouldn't be a bad idea to check the carb float level and verify that isn't the cause of your rich running condition. It is possible that you have a lower end crank seal leaking contributing to the spooge you're getting out the exhaust but normally that will show up as a gooey spark plug. You said you had a dry sooty black plug so I sorta doubt that you'll have the lower-end oil leak issue to worry about. I think you're very close to a nice running bike as long as the motor was assembled right.

MX Tuner

Editors Note: There is no jet in the fuel petcock, opening it 1/4 limits fuel flow which should be controlled by the carb float & needle. This may be disguising a problem with the float height, float needle, & needle seat.

FMF/Wisco Jetting Changes?
Hi I have a 98 KX 250 mostly stock except for Wisco piston and rings and I added a FMF fatty pipe and I moved my jetting to a 162 from a 158 and I'm running 32:1 Gas mix and It's running rich and I haven't moved my throdel needel yet because I not shure. I lost a lot of bottem end from it I am planning on buying a new fmf slincer and I'm wondering if that will fix it or if I should change the jetting again.

Thank you, Clayton

Chances are your rich running is due to the pilot circuit, not the main circuit. When rejetting, you need to do the main jet last. First, adjust the pilot jet and air screw, then the needle position once you get finished with the pilot, and finally the main jet if you think it needs it. There are a few good on-line jetting guides. Try www.eric-gorr.com for one of the more accurate guides.

MX Tuner

I Need to see Pictures
I have a 1993 Kawasaki KX 125 and I need to know where I can go on the web to find out how to split the cases and replace a rod bearing.

I need to see pictures!!!!

Any help would be appreciated!!!

Thanks, Chris

You need to buy a shop manual. I don't know of a reputable source for that type of information. You'll need torque specs, measurements and other info that will all be contained in a good manual. And it will even have pictures. If you try doing it without the correct tools, you stand a good chance of doing expensive damage. Some tools are nice to have, and some are virtually a requirement for doing the job properly.

MX Tuner

Super Foul
I just bought a 2000 YZ 125. It has already fouled 2 plugs when I am warming up the motor and start increasing the RPMs. It usually takes a good 10 mins to foul it completely. After I change the plug and start riding out on the track (I ride with the motor screaming most of the time) the plug will last all-day and run like a top. Also there is some black spooge coming out of the silencer.

desperado

First thing to do is check the float height. Check each side of the float since one side can be too low and the other can be too high. I've seen bikes right off the showroom that have bent floats. Once you make sure that is correct, you can start by going to a leaner pilot jet. That and quit using the G or V tipped spark plugs. The best plug for your YZ is a BR9ES.

MX Tuner

Transmission Leak - Oil Weight
I have recently purchased a 1996 Yamaha WR 250. What weight of transmission oil should I use, and how much does the case hold. I have currently started using Bel-Ray Gear Saver SAE 80W and my transmission leaks during operation, but does during storage. Do I need to switch oil or replace gasket?

Your WR will shift much better using Type F automatic transmission fluid. There is a number cast into the side cover near the oil filler plug. This is the capacity of a dry transmission. It would be safe to put in this amount during a fluid change. The ATF, as well as any oil you use, should be changed fairly frequently. Every other ride isn't too often. The ATF is cheap and will work better than the Bel-Ray gear oil. Yamaha lists an automotive engine oil specification for your bike. That will also work as well as the high-dollar Bel-Ray.

Concerning your leak, wherever it is leaking from needs to be replaced, regardless of when it is leaking. For instance, if it is the countershaft seal leaking, it needs to be replaced. Shifter shaft seal? Same thing. Replacing the seal should fix the leak.

MX Tuner

Water & Oil
Year: 1989 Make: Suzuki Model: RM125
I bought my RM 125 just recently but have no experience in mechanical side of things. The bike goes great! Now the problem that I am having is that there is water getting into the area of which the engine oil is kept. Also the radiator water is getting bubbly, I don't know what it means. Would this cause serious damage if I keep using like this. Do I need to rebuild the whole engine or should I first try the water pump area.
P.S. Which oils do you recommend?
Thank You

Murat
Melbourne, Australia

Unless the case is cracked, about the only place water can get into the gear oil is from the water pump seal. It might be a good idea to replace the water pump shaft, bearings, and seals all at the same time since the bike is almost a teenager. Oil in the coolant will soften and swell the coolant hoses and the water in the gear oil will reduce its ability to lubricate and protect.

Suzuki specifies an automotive oil specification. Most any oils, or Type F automatic transmission fluid, will work just fine. Any oil you choose, even the motorcycle specific oils need to be changed frequently.

MX Tuner

Clutch Drag
I recently had my clutch system repaired on my '89 YZ 125 but apparently, a problem still exists. The clutch is very stiff to engage and when I shift down to first to take off the bike surges forward before I release the clutch showing me that the clutch is at its friction point. What can I do to adjust this? I am new at dirt bikes and need advice.
Thank you, Daniel

Sounds like the clutch cable may be stretched, dry and binding. First thing to do is lubricate the cable with a pressure luber and WD 40 or Tri-Flow. Be sure to grease the hole in the lever that the barrel end of the cable goes into. This should address the stiff lever pull. The clutch dragging may be due to the cable being stretched or due to the clutch itself. If someone installed stiffer aftermarket springs, (Barnett or EBC for instance) that could be the cause of the dragging. The stiffer springs are usually too stiff and should rarely be used. If the clutch basket or hub has notches in them where the plates ride against them, this could also be contributing to the clutch not releasing properly. You may have to remove the clutch plates to inspect these parts. If the metal plates were not replaced, they could be warped. This can also give the dragging symptom.

MX Tuner

Wet Plug
I have a 94 KX 250. It has a Boyesen RAD valve, pro circuit platinum pipe, and matching pro circuit silencer. The problem is it's blowing black oily stuff out the silencer and fouling the plug (wet but no carbon) when you ride 1/4 to 3/4 throttle. WOT performance seems great. I can still ride through 4 gears with the front wheel off the ground so the bike does run good and always starts on the first kick without the use of the choke. The main jet is a 162 and pilot jet is a 45 with the airscrew a full 2 turns out. I notice a bit of purplish color on the front of the pipe when I ride. I'm not a racer and only ride on trails and sand pits. Any suggestions?

Gary

I'm almost wondering if you have a crankcase leak letting gear oil into the motor. Normally a rich condition (which give the spooge out the silencer and plug fouling) will give a spark plug that is dry and sooty looking. If you have a "wet but no carbon" appearance to the plug, that can be an indicator of a bad right side crank seal sucking gear oil into the bottom end. The fact it starts first kick without the choke is a sign that the lower speed circuits are too rich. Check the float level to verify that isn't giving an abnormally rich condition. If that is okay, I'd start out by going to a 40 pilot jet and fine-tuning the off-idle throttle response with the airscrew. Then fine-tune the throttle response in the ?+ throttle settings with the needle position.

If it is still spooging after that, you may very well need to investigate a crank seal leakage.

MX Tuner

XR200 Mods?
I have a couple of questions. I heard that the 1985 XR200R cannot be bored out - is this true? If it can't, can I use a cylinder from a 250R of the same year or close? What about an aftermarket cam? Does anyone offer one or can I use an aftermarket one from the 250r? I have totally replaced all of the internal components due to a failed crank bearing. I wanted to see if I can bore it out because of all the money I spent I want a little more power if you can't help do you know anyone who can? Thanks for any and all help

Personally, I'm not familiar enough with the XRs to know what parts do and don't interchange between models. You might check with either Stroker Racing or Thumper Racing for some better advice. These guys do nothing but work on four strokes like yours all day long. These guys are the people I call when I have a question concerning possible options.

MX Tuner

Dripping PW
I picked my son up a '84 Yam. PW 80. Dripping from carb overflow while riding, floods and stalls about a minute after stopping. Will drain on ground if gas not shut off. (over time) I'm thinking worn float needle, seat? Float looks good, no leaks. Also could you please suggest an airscrew starting point & oil mixture ratio. This is kinda fun compared to pulling the carbs off my '91 VFR. Thanx for all the good reading & tips.

jimmy.

Definitely sounds like a worn float needle and seat. Your airscrew should be set at 1 ? to 1 ? turns out. If the oil system is disconnected and the oil line fittings plugged (to insure against air leaks) then 40:1 will do nicely for the PW.

Yeah, the VFR is no cakewalk when it comes to carb work. But even that is easy compared to doing a valve adjustment on something with shim under buckets with four cylinders.

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Bottoming Out
I have a 95 KX 100 and the forks aren't stiff enough I've used all of the adjustment and I think it might need a rebuild. I am bottoming out on one of my jumps. I am jumpin about 20ft and my friends say they can hear a loud crack when it bottoms out it hurts my hands too. I was wondering if you put new seals in yourself and more oil will that fix the problem

If the seals aren't leaking, then replacing them won't help reduce the bottoming problem. Hard to say exactly what the problem is since I don't know how much you weigh. The stock springs may be too soft for your weight. Stiffer springs could help significantly. But chances are the oil is the biggest problem. If it is old and contaminated, it can't do its job properly. If the oil level is too low, that will give a bottoming problem. You can add oil to each fork leg in increments of about 10ccs at a time until the bottoming is reduced. Don't expect it to eliminate it completely, but it can bring it to an acceptable level.

You can switch to a thicker viscosity oil but then you give up plushness on sharp edged bumps.

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Ramp?
I am looking for a fmx ramp. Do you know where I might find one?

No.

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PW 80 Needs More Power
I bought my daughter a '01 PW 80 about a month ago (her second bike). The bike is completely broke in and the problem remains:

When accelerating, just when it feels like it's hitting the power band, the bike starts sputtering (at about 1/2 to 3/4 throttle). I've removed the restrictor from the pipe, and the problem remains. Plug looks good. I've been told that it's simply the way PW 80s run, but it seems to me it is running a bit rich at the top. Other than removing the restrictor, the bike is completely stock. I am at about 4500 feet with the majority of our riding at 4500 to 5000. I want to try moving the clip on the throttle needle up a notch but am not sure if this will effect the way the oil injector works (the PW 80 has an odd ball injector that pipes strait into the carb). Any suggestions on squeezing more power out of this bike?

My daughter rides the bike with the throttle cranked wide open about 90% of the time.

Eric

Ah, a speed racer, eh? Maybe a future national champ!

I think your suspicions are right on the money. Don't worry about jetting changes affecting the oil injection. You'll get plenty of oil regardless what you do, jetting-wise. I'd order a couple leaner main jets from the dealer. You may very well have to go down two steps to get it to rev normally at the altitude you're at. They come pretty rich anyways and the lack of oxygen is just aggravating matters. The needle position may help but I think the main will be the cure to your problem.

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Permanent Vacation?
I have a 1995 Kawasaki KX200. It had been sitting awhile. It was run for the first time this weekend. It ran fine one day then, the next day the spark plug got ruined. We bought a new spark plug and it still wouldn't start. When we tried to jump start it, it would make a backfire noise like it was out of gas. My cousin thinks that the oil in the gas settled and clogged something up. If you have any ideas or know how to fix this, I would greatly appreciate it. Thank you very much for your time.

sincerely, steve

The backfiring is a dead giveaway that it isn't getting spark at the right time. I'd check the keyway for the flywheel on the crankshaft. If this has sheared, it will give the exact symptoms you describe. Either that or you may have a CDI box that has just taken a permanent vacation.

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50cc to 80cc
I have an 87' Yamaha DT 50 on which I recently fitted an 80cc cylinder and a 21mm carb. Now the engine overheats so the spark plug goes bust after just riding it for a couple of minutes. What could be the most likely cause?
Thanks for answering!

My first guess would be jetting that is too lean or an air leak. Next might be compression that is too high and possibly even detonation. I don't know if the ignition timing needs to be changed to compensate for the bigger bore either.

Even a restricted exhaust can cause an engine to run abnormally hot. I don't know if the 50cc exhaust can handle the 80cc flow.

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