jse

There is a very small ball bearing between the clutch rod and the "mushroom" that presses on the pressure plate, you might want to check that it is there. The servo cylinder piston would probably be at it's stop if the ball bearing was missing. Jon

Tom, Since the Pro is a bike made for full-on competition such as flinging about on rocks, slopping through mud and at times being submerged under water and yours is about 8 years old now, you may want to spend a little time getting things sorted out before writing it off. When buying a used bike (any bike and especially one 8 years old) it's best to assume that it has had no maintenance whatsoever and start from the beginning. A new sparkplug properly gapped, cleaning of all electrical connections and grounds, throughly cleaning the carb and adjusting it when the bike is running, through cleaning of the airbox and filter, inspection and cleaning of the stator area, checking of the wheel-suspension-steering bearings, spokes, checking all fasteners, changing out all fluids etc. is a good way to start. Most present and future problems will be solved by proper maintenance and you will get to know your bike much better. Jon

Sam, Check to be sure the pressure plate is "indexed" to the hub by looking for the spring hole in the pressure plate with a line marked near/across it and that the spring tower that goes through that hole has a line across it. The pressure plate goes on the hub assembly one way. Also be sure the adjustment screw on the clutch lever is backed out enough to provide some clearance between the screw tip and the plunger rod that goes through the M/C boot. Screwing the adjustment in too far will cause clutch slippage and a hard lever, when the piston bottoms out in the M/C cylinder bore. Jon

Yes, the last the three prototypes I made. In spite of the length, it fits in closer to the frame than the stock pipe. Back to the airbox problem, it might be a good idea to tape the seat before a wet Trial as the seal on the seat can sometimes allow some water through (past the area where the o-ring ends meet at the front of the seat). I also use Silicone on the junction under the rear fender where the fender meets the box and have re-sealed the box/seat framework junction. I cut about 5mm off the duckbill valve in the bottom of the box to allow better drainage as I'm more concerned with water being able to get out of the box than water entering the box through the valve. Like I mentioned, the major problem I had was water over the engine and into the intake under the back of the fueltank. I've ridden in some really nasty conditions now and not had a problem with water ingestion. Jon

Cool! I suspect, however, that I'll need more catching than wrenching..... Jon

I'm going to miss the event as I'm in Germany right now and won't be back in the U.S. till after the weekend, darn it! If you have not made the NTTA CRTC 2-day, you have missed a great Trial. In addition to the cheerful glee put forth by the comedy team of "Danny & Ramon", the NTTA people know how to make you feel welcome and provide a challenging course with neat sections. Don't miss it! Jon ps. Since I can't make it, I know the AVTA guys will fall down a couple of times in my honor, just to make me feel good.....

Dan, I told Dale I'm ready to take over the GG #1 spot, but only if Pat agrees to be my minder.... It's going to be interesting to see how things work out, but those kids can be champs on whatever brand they ride. They both are amazing and I love watching them, plus we've got some fresh new Pros who all show good promise. I was very impressed with the new champ riders drive and talent at the OK National. Jon

Tom, Dexron ATF is probably the best fluid to use in the 03'. You mentioned taking out dirty grey oil and if it is a light grey, you may have coolant in the trans fluid which will affect clutch action. The adjustment screw on the lever must not put any pressure on the plunger that goes through the rubber boot with the lever out at rest-ever. If the first part of travel of the lever does not build pressure there is a possibility that the seal in the master cylinder needs replacing. The master cylinder bore will have a slight taper after a few years use with the first part, under the most use, having a slightly larger diameter. The seal lip, being worn (smaller diameter), will not seal during the first part of travel but then start to seal when it hits the smaller part of the bore. A master cylinder rebuild kit will solve this. Turning the screw in will temporarily "help" the problem by starting the piston further down into the bore, but it will create a bigger problem by sealing off the bleed hole (between the bore and the reservoir) which makes it a "closed system" that can't equalize itself and your clutch problem will rapidly increase. Jon

GasGas changed the airbox in 03' to include a removable plastic shield over the filter (I have an 02' with a later model airbox installed). The problem is that the front tire throws mud and silt up through the open area under the radiator and then over the engine and into the airbox intake, which then dribbles down on to the air filter and is sucked into the engine. I also made a shield that fits in the open area under the radiator to keep mud off the engine and from getting into the airbox and you can buy these from most Trials dealers. The shield should really help keep the airbox a lot cleaner. Jon

Another thing I usually mention to a new rider changing oil is to use a new Allen wrench or an old one with about 5mm cut off the end. The drain plugs are aluminum and easily stripped out unless the flutes on the wrench end are sharp. The lower plug uses an aluminum "crush" washer so it's a good idea to replace it once in a while. Jon

My guess too. Could be a bum seal so it would be a good idea to take off the flywheel and check. There also is a case capscrew that has a copper washer on it (upper right-hand I think) to seal an oil passage and there is a rare chance that might be leaking. Jon

Thanks. My motto is that my knowledge only gains value when I give it away. Jon

Kay, Take a look at your bike and see if the info fits what you see. Any questions will be happily answered by the forum regulars. Jon

Humph. That Jon guys sure gets around....... Jon

Not sure what model you have but the newer Pros have actual 177mm fork and 164mm shock travel. Race sag is a much better measurement than static sag as it takes into account the actual weight the suspension will be dealing with. So, on that basis, race sag (all riding gear on and bike upright)should be in the range of fork: 59mm (2.32") and shock: 55mm (2.17"). Jon

Kay, Oil volume in the Pro seems to be (to me, at least) a mildly baffeling subject in that the factory recommendation seems to call for too much oil at 550cc's, from what riders tell me (and the recommendations vary slightly from year to year in the earlier spec.'s). Riders have complained that overfilling the cases leads to the excess being dribbled out the vent tube. The general agreement seems to be to fill the case to just about the top of the sight glass (bike upright and time allowed for the oil to circulate) and this seems to work out to about 425/450cc's in most cases. My 02' 280 Pro, for instance, takes 375cc's to fill the sight glass to the top because it is a slightly different engine than your 05. I think the more important issue is to change the oil often to keep it fresh as it does double-duty in the Pro and lubricates the crank bearings, for instance. Jon

Both books are excellent and I have them in my technical library. Jennings' book is still probably one of the best and a good starting point for gaining a basic understanding of high performance engine design. Both, however, do not incorporate technological advances that have occured since 1983 (Bell) and in Jennings' case, 1973, and are oriented towards high-RPM, maximum load engine operating conditions rather than the low-RPM, variable load, on-off throttle operating conditions we experience in Trials. Just as I would choose a different oil and ratio for the roadrace engines I built, compared to, for instance, the Motocross, Supercross and shifter kart engines, I would choose a different oil and ratio for Trials applications. I run (full-synthetic) 50:1 in my air-cooled Trials bikes and 70:1 in my liquid-cooled model and have monitered all of them carefully for problems, of which there have been none relating to lubrication. Around 80:1 seems to be the general choice for most Trials riders running the 125cc and up displacement engines, but I also agree that you should run the oil and ratio that you feel comfortable with as I've rarely seen an engine experience mechanical damage from too much oil, only performance deterioration. Jon

The least expensive way is to buy your buddy (who owns the same type bike) a few beers (more beers=quicker "yes" answers) and ask to borrow it. Swap one piece of the system at a time to isolate where the problem is. Don't forget the cheap parts, like the plug cap, as they can stop an engine as quick as the expensive parts. Jon

I can't figure out where they would go. Are you sure these are for a Trials model? Jon

Although it's recommended up to 50:1, I think this is for high-speed heavy-load applications and Trials, of course, is a unique use with less severe conditions. I too have run TTS for years at 70:1 and have had no problems or issues. Jon

Check the clearance at the adjustment screw on the clutch lever. Not sure if the Sherco uses an "indexed" pressure plate like the early GasGas (mark on the pressure plate lines up with mark on spring tower). Jon

Since it affects all the gears, I agree with Copey (jeez, never thought I'd say that). Check the racheting mechanism, especially the spring that puts tension on the roller that drops into the slot between the points of the "star" on the end of the shift drum. The roller locks the transmission in each gear. Jon

If it was fine before the crash and not after, look for something mechanical on the outside of the bike, like a problem with the lever, loose fitting (you should see weeping oil) or at the master cylinder. Chances are the problem lies on the outside of the engine, not inside.

The video for the Pro W/P repair at http://www.trialspartsusa.com/youtube.html should help you. On a 2002 model you should probably replace the W/P shaft also. Not sure what you meant by the thermostat blew off, but make sure the overflow tube off the radiator is not pinched by the underside of the fuel tank. Jon ps.Just remembered something else (when I posted the above, had just got home from a long 2-day event). If the small brass plug on the side of the pump has an Allen type center, you probably should replace it with the updated bushing (it is the outer support for the impellor shaft) that will have a Torx type center. Also check the W/P shaft where the seal lip rides with your fingernail to feel if there is a groove there and if you find one of more than a slight indentation, you probably want to change the shaft to the newer type. If you don't replace the shaft the new seal lip will ride down in the groove and contact tension will be lessened and the seal's service limit will be decreased considerably. The fingernail is surprizingly sensitive to small depressions/scratches on surfaces and is good for finding pits/cuts on fork tubes that are easy to overlook with the eye. I updated the pump on my 02' Pro with the newer parts years ago and have not had a problem since. ps, ps (still waking up....) There is a very thin o-ring on the pump housing to keep oil from weeping from the trans. Be sure to grease the o-ring and put a little on the housing (and don't forget to index the pins on the W/P shaft to the slots on the crank primary gear). Carefully install the W/P housing in straight in order to not damage the o-ring, which is relatively simple without the hoses attached. If the hoses are attached, they will pull on the the right side of the housing a little and the pump will be canted so you will want to push a little on the left side of the housing and pull a little on the hoses to keep the pump straight while it slides into the sidecover. If you just push the pump in and it's not straight, when the o-ring (which is very thin) slides past the first part of the machined bore of the sidecover, it will shave/cut off part of the o-ring and cause oil weeping around the W/P eventually. O.k., now I think I'm done......