jse

I'd look into an alignment issue ("stiction"), if the forks worked o.k. before the work was done. I'd loosen all the fasteners (especially the fork brace and axle) except the top triple-clamp bolts and work from the top down, pushing on the forks to "center" them with each new set of fasteners tightened. The fork brace is always last. Jon

This fork brace has been giving me good service for about 12 years now: Jon

dadof2, looks like it to me too. There should be a thin steel washer on the hub shaft and, like the kickstart shaft washer, usually sticks to the sidecase and clutch basket hub and falls off before reassembly. Based on the contour of the grooves and location, I'm wondering if a tang broke off the shift centering spring and got caught up in the back of the basket. It still does not explain the steel bits on the sump plug magnet, which will need investigation. And thanks for the compliment for the videos (and all the other info on his website) but they are made by Jim Snell, the parts importer for GasGas in the U.S. Jim has probably forgotten more that I know about the GasGas bikes.... Jon

Dark brown not bad. Reading plug color is only an approximation in a Trials bike due to variations in throttle and load. If you were running an engine under load and full throttle you would generally look for a milk chocolate color, but even that is only a few of the things you look for when "reading" plugs. Jon

I add a breather to all my Trials bikes, since the early Bultaco days. Never had a water ingestion problem. Jon

Might want to raise the needle one notch and go up a little on the pilot jet for a start. Jon

You guys have yet to catch up with me, I wander into a house and ask "Who's house is this anyway?".......... Jon

I agree and would add to drain the tank and carb completely. Fill tank with fresh premix (from the station, NOT an old gas can). The carb, tank and gas can lose the "high-end aromatics" in fuel that are there to aid starting and their effects are cumulative. Using fuel from a stored can, if plastic, means you are not starting with "fresh" fuel and may need to change your storage techniques. If this makes the bike easier to start, it could be your problem. Jon

I have more than serious doubts that a mixture change of one turn on the fuel screw had any overall effect on the engine damage situation (it has the most effect in the idle circuit metering to needle-draw transition) . The 150 vs 850 meters (jetting wise, a change of about 2300 ft., and a much bigger gap at the 1100 to 1200 altitude) could result in an overall lean mixture (if running well at 1100/1200 meters) and this may likely be a contributing factor. Experientially speaking, engine damage of this sort is usually a combination of several issues, a "perfect storm" you might say, of miss-adjustments (lean mixture due to main jet/needle adjustment, old fuel etc.). It would also seem that it is the responsibility of the new owner of any used bike (knowing-or should have known, for instance, the change needed in jetting due to altitude) to set up the new bike before use. Knowing the above new information, detonation may be the primary cause. Detonation usually announces itself with dramatic engine noise, which in this case was possibly ignored and/or misunderstood. Jon

Trials is a sport that always welcomes back riders who may have given it up for whatever reason, unlike most participant motorsports I've experienced. It must be the type the people that are attracted to it, they are a different bunch. I started in 1971 and was out of Trials for a couple of years some time ago and one of my wise Trials friends said to me then "Ya know Jon? Riding Trials is like smoking cigars or riding Ducatis, you may give them up for a while, but sooner or later, you'll be back!" He, of course, was right and I'm enjoying the sport more than ever...... Jon

Welcome back! I'm actually flying out your way for the weekend in a couple of hours. I also started riding Trials in the very early 70's (lived in San Jose at the time) and was a member of PITS. You'll really like this Forum, it's a world-wide hub of information and collective knowledge and there is something on here for everybody. Cheers! Jon

The trans breather hose is NEVER connected to the carb. Jon. ps. I'm not aware of a "TXTI" model. The 02' Pro was a "TXXI" model but known as the TXT Pro 03' forward.

Oh, and I meant a straight blade screwdriver. It's tougher with a Phillips blade......... Jon, wrong yet again.........

Take a very small Phillips screwdriver, place the tip in between the overlapping strips and twist. Jon

That's a new one for me. I can understand the impellor stripping, actually fairly rare from my experience as usually caused by the rider taking the brass plug out of the pump to drain the fluid and the thrust washer falling off the shaft end and into the housing and binding the impellor to the housing (it also allows the shaft end to sit into the housing too far and the impellor scrapes the inside of the pump housing, and I don't see signs of that here). Obviously it's hard to see details in the photos, but I don't see any obvious signs of detonation but the rings seem to be seized in the lands (could have happened due to excessive heat, and "after the fact" of the main cause). The hole in the combustion chamber is unique, however, and may have been a surface fracture that let loose and a possible cause of previous overheating issues-chamber gases pushing into the cooling system. I think that's the first one of those I've seen. You could not have normally predicted a material failure of this sort unless you carefully inspected the chamber for cracks while the engine was torn down (not a normal proceedure in my experience other than in high-end racing applications). It does look like the engine was stopped (locked up) when the chamber wall came apart (and the piece got stuck in the squish area) but it also seems that this engine was run beyond the time it should have been shut off when the first overheating symptoms were noticed. First rough guess is material failure in the head chamber. Jon

The answers are probably "no" and "yes". Jon

" He sent me some pics of the cylinder head which has what looks like a melted hole in it, another pic of the piston which seems to have a piece of metal stuck to it and another pic of the cylinder inside which has a big gouge in it (I think from the metal that is stuck on the piston)." I don't think I can remember knowing a rider who would continue to ride a Trials bike, with the obvious symptoms of distress the engine undoubtedly exhibited, to the point of this type of damage. I think there is more to the guys story than he is telling you..... Jon

With no leaks noted, one would suspect an inner crank seal allowing trans oil to be sucked into crank area under vacuum (especially if you noticed an unusual amount of smoke from the exhaust). I would always look at the simple things first, that being the trans breather (I'm assuming this is a Pro). It's the small right-angle fitting and hose in front of the countershaft sprocket (the hose goes up and loops under the tank), be sure that it is clear, otherwise pressure can build up in the trans casing and force some oil past the crank seal lip. Excess trans casing pressure symptom is usually weeping from the outer seals but not always. The crank seal is vunerable due to the normal pressure differentials it encounters. Jon

You were correct. Jon

Thanks Martin! I'll pass it on. Cheers! Jon

Generally the clutch system will not "suck" air as it is usually under pressure. What can happen, and it's not uncommon, is that the rubber boot at the M/C will get torn, loose or for the earlier models gets enough brake fluid (DOT 3,4,5.1) on it to deform and allow fine grit to enter into the piston bore. This will wear the o-ring and piston (like grinding compound), which will allow a little air to pass by the o-ring under the slight vacuum it experiences at times and wear the outer lip of the piston seal. As the bore of the M/C can/will be worn to a slight taper, eventually the outer diameter of the seal will become smaller from wear and not start to seal when traveling down the bore until it reaches a smaller diameter of the taper. This is usually noticed after the bike has not been used for a while as the piston seal lip "relaxes" from the normally curved profile it assumes while in use. Jon

Chris, If the stock shock is on your bike, it's undoubtedly a Sachs unit and not normally rebuildable. Make sure the Heim Joint at the top of the body is in good shape (it should not be loose at all) and lube the suspension linkage well. Some shops can drill the shock body for a Schrader valve and replace the oil and Nitrogen. I'd suggest taking the shock off, removing the spring and checking the damping quality for a start. On the linkage, make sure you also get the two needle bearings up in the swingarm, they are often overlooked. Jon

My experience also. The finger height is the defining measurement, rather than the clutch pack width, which is an approximate. Jon

If you don't see a cut and welded flap on the backside of the mid-muffler, the previous owner may be making it up. The rewards of a quiet exhaust compared to any slight increase of power (and loss of power at lower RPMs, where you will spend most of your time) is much greater. Your fellow riders will throw fewer rocks at you..... Jon

Sometimes that will work but only if the lip on the bearing-puller collar can catch the edge of the bearing. It's a very tight fit. I use a long, thin drift and dress the end flat so that it has a sharp edge. Lightly tap the inside bearing outer race, rotate the drift a third rotation, repeat. Works a treat. Jon