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What air pressure do you usually run in the back tire? Jon

Rear tire should be tubeless. If for some reason someone has put a tube in, 3.50-4.00/18 Jon

I think you didn't get any answers because we'll need to know the year of the bike. They used several types of CDI systems. Jon

Just think, you'll be an expert soon. The spear-like shavings (as opposed to the "fuzz" type) on the magnet usually are from gear teeth, possibly the idler gear. They are rolled off the end of the tooth face when gears get worn. Jon

Hi UncleJosh! I see you live in my home town. Spent many happy hours in High School surfing at Steamer Lane and cruising Beach Street during the cold, foggy nights of a Santa Cruz Summer. I would think that the split needle bearings in the tranny are only "consumable" if the previous owner was lax in changing oil regularly. The Pros need fresh oil as there is a lot of stuff to lube in the engine, but Dexron is relatively cheap. I agree that the kickstart idler gear should be checked as they don't take kindly to abuse. You also might want to see if the clutch basket has excessive play (there are two sets of caged bearings separated by a wire spacer). A problem with the K/S idler gear will usually be a clicking sound if a tooth is damaged, but I've heard one whine a little because it had excessive wear (the teeth will be somewhat sharp and have a slight "lip" on the upper part of the tooth face). Excessive gear lash may also be a function of a worn clutch basket gear and/or primary gear (on the end of the crank). As to the particles on the magnet, if they are like a little tuft of black fuzz you can wipe off with a shop rag, that is somewhat normal but if they are actually small pieces of metal, it might be more serious and an engine teardown and close inspection might be prudent. Jon

Andy, I'm guessing that there may be some binding in the movement of the arms the floats ride on. Sometimes the head of the float needle does not move smoothly on the tab on the float arms. There are only a few components on the fuel level regulation assembly: the floats, the float arm/pin, the thin rods the floats ride on and the needle valve assembly. Unlike the fuel delivery system that has a lot of disimiliar components that overlap in operation, the float level system is essentially digital and is on or off, so it could be something simple like a rough spot or manufacturing burr that is hanging things up. Jon

It looks like you got a rebuild kit for the rear master cylinder, not the front. Jon

I think it has a strong adhesive to hold it in. If you clip off about 10mm from the end of the wire, you will have a new, clean wire contact area for the plug cap to screw in to. Jon

Actually, that doesn't look too bad to me. Some riders use a file to straighten the sides of the fingers but that may cause a little more "slop" in the drivetrain. I polish the sides of the fingers and the slots on the hub (all the friction points the plates make contact with) with a rubberized abrasive called "Cratex" and I think it helps the plates move easier and results in smoother clutch operation. Jon

Nath, I'm not absolutely positive, but I would think the JTX320 is a direct swap as, to my knowledge, only the topend components are different. Jon

I'm trying to remember, but I think the hub nut has a very fine thread pitch and you may want to go a little less so as to not strip the threads, maybe 25 ft lbs? The locking "pressure" is carried over a larger area with the fine pitch. Red Loctite would be a good idea just to be safe. Jon

There is a line (like lightly hit with a chisel) on one of the spring towers and a mark by one of the spring tower holes on the pressure plate that need to be aligned. Jon

OK, well tore the bike down. Here are the findings: Clutch - lever returns nicely to the circlip, then there is some freeplay with the levler (looks good to me) - pulled off the clucth cover and put a dial guage on the clutch stack - as soon as the lever engages the clutch pack starts to move (good thing) - the maximum movement of the clutch pack is .035" (0.89mm) - pulled the clutch pack apart and measured the friction plates they are all about 0.013" (0.33mm) thick ***Those spec.'s do not seem too bad. You might want to line the springs up on a flat surface to see if any have sacked out, which would cause drag. - found one issue: the nut holding the basket on was not tight, I was able to turn it off with minimal torque. There was no locking tab either, although I am not sure how one can fit inside. ***I think only the 125/200 models of that year use a locking tab. - any idea what the clutch specs are for this bike? ***I don't have a plate to measure but the fact they all measure the same amount indicates they are probably good. Kickstarter - the shaft is loose in the casing, but quite snug in the cover - the cover bore seems OK - I cannot tell if the spring is distorted - not sure what to look for here - when I try to put the case together with the shaft, it is binding somewhat - I put the kick start shaft between to centres (on a lathe) and measured runout on the to bearing surfaces - .001" tops ***I don't think the 2000 uses a bearing on the case side of the kickstart shaft, just a machined recess. The spring spacer may be binding the spring operation or holding the shaft out somewhat. For a 2000 TXT parts list try http://www.trialspartsusa.com/tech.html and you can download the manual to see what the spring should look like. Jon

In my experience, the fan will vary speed according to engine RPM up to about 1200 RPM. Jon

(1) Very bad clutch drag. I know it could be anything from master cylinder, to the clutch line, to swollen discs - Suggestions on the easiest diagnosis? Make sure the M/C piston is returning back fully to the circlip, this may require backing off the adjustment screw on the lever. When pulling the lever in, you should get pressure soon into the stroke, otherwise the piston seal may be worn and need replacement or there may be air in the line. I'd also take the sidecover off (when you check the kickstart shaft) and check the clutch itself by taking it apart. (2) BRAND NEW Electric fan is intermittent. It started to overheat, and fan wasn't working, so I jumpered the thermostat in the field - still didn't work. Road the bike a bit, then it started to work. Drove more and it didn't. I guess its either the alternator, regulator, rectifier or the NEW FAN is busted. Suggestions on how to diagnose? If the fan runs on a 12V source, it's probably o.k. The fan module is probably the next suspect in line followed by the voltage regulator, thermoswitch and then the stator output. All components should be checked after making sure there are no worn wires, loose connections, corrosion etc. in the electrical system, of course. Intermittent operation of the fan is normal, otherwise you would not need the thermoswitch. (3) The kick starter does not return. I have to return it by hand, and it is a bit of a struggle to return it back to position (i.e. VERY sticky). How do I determine what part is bent? You will need to take the sidecover off and look. Check the spring for distortion and try to figure out where the assembly is binding, in the sidecover or where the shaft goes into the case. Jon

Dr. Blair did do most of his research on the two-stroke from what I gather. I knew of him mostly through the software development. There is a lot of overlap in theory and practice between the two and four-strokes as the Laws of Physics apply equally, so I'm not surprized he would have also been interested in 4T valve systems. I started out working on both two and four-strokes but then specialized in four-stroke design as that was the dominant engine in the type of racing I was doing at the time (dragracing). Later, in the late 60's I also specialized in two-strokes as that was the predominant engine design for the racing I was involved in then (MX, dirt track, roadracing and Trials). I guess one's skill development follows one's curosity and interests. Walter Kaaden's theories seemed to be driving force in expansion chambers, kinda like Harry Ricardo was for combustion chamber design or Adolph Schnurle for two-stroke porting. Before their innovations, the two-stroke was just an underpowered industrial curosity from what I can see. Jon

I didn't know that. Very sorry to hear of Dr. Blair's passing, about a year go as I understand. He was a looming figure in the area of two and four-stroke engine development and I've read a lot of SAE papers he authored. I still use a lot of engine design software developed at QUB under Dr. Blair's supervision. Jon

I also have a 2002 280 Pro and use the GM AutoTrak II in it (350cc's). The earlier models cn use the GM or Dexron (which gives a little more "bite" to the engagement) and the 2006 upwards (with the thinner Belville spring) seem to be happy with the Type-F ATF which has little more heat tolerance than the Dexron. The lightweight motorcycle specific trans fluids work well, like the 75-weight (which is actually more like an engine-specific 10-weight as trans and engine oil viscosities are measured at different temperatures). I doubt that the one plate would produce your symptoms (the other two should release if that is the case). I think the fiber compounds/face patterns were revised in 2003 (I have a 2004 pack in mine, for the last 7 years, no problem). What did your clutch measure out as (clutch hub to finger height)? You might have a problem with the o-rings leaking on the top hat post that will not give you a full release when cold but will seal when warm and expanded. Jon

Hi Curtis! Jon here. As I mentioned in a previous post, I've not had research experience with Ethanol, but from personal experience, Methanol race fuel systems require a complete flush before any storage due to corrosion caused by any alcohol left in the system, so I wouldn't be surprized if the Ethanol is causing some component problems. When I lived in Northern California, we also had a big problem with another oxygenation compound, MTBE (Methyl Tertiary Butyl Ether) that contaminated the lakes and watersheds due to watercraft exhaust. If you were filling your tank and some of the MTBE vapor managed to sneak past all the anti-vapor attachments on the pumps required in California, the stuff would just about knock your socks off. My understanding was that it was used because it was cheaper than Ethanol and it that was true, yet another example of profit before responsibility. All the stations here in the Midwest proudly display large signs if they carry Ethanol free fuels, so it is apparent that the public has an affinity for avoiding the oxygenated fuels. As such, it puzzles me that the best and brightest minds in the U.S. Chemical Engineering industry can't come up with an emission reducing compound that solves the problems and the public wants. Jon

You must have read one of my articles. I'll count you as one of my 5 fans.... Like I mentioned in the article, the sidevalve is limited in higher RPM situations, but would be, for a 4T engine, just about perfect for Trials use. Last time I heard, they had brought in another engineer and were working on valve size/placement. I think the economy and the "iffy" reception the FIM mandate for 4T's in WTC received in the Trials world put it on the back shelf for a while. The design may look very simple, but to optimize it's potential, you have to really understand how they work. The engineers ought to get hold of one the old factory Harley flat track sidevalves (pre-XR750), those things were developed to within an inch of their lives and put out scarey horsepower. Jon

You can try a snap gauge and caliper, but at the tolerances that the piston/cylinder clearance is held to (.0015/.002") it's not possible to be accurate to any large degree. You can get a relative estimate of ring wear (and extrapolate that to cylinder/piston wear) by measuring the ring end gap of the old rings (square ring in cylinder about 10mm down from deck and measure end gap). Knowing that the newly installed end gap is about .1mm per inch of cylinder bore, you can get an idea of how much the rings (and the cylinder/piston relatively speaking) have worn. The piston kits come with a pin and new circlips. Be sure to check the cylinder for signs of excessive wear of the Nikasil lining. Usually about 10/15mm down from the top ("deck") of the cylinder on the exhaust side (known as the "thrust side" where maximum piston/cylinder pressure occurs during the combustion cycle) is a good place to start. The best way to measure clearance is a dial bore indicator and micrometer. I'd also look at the airbox/filter/boot areas as there may be a problem with grit passing into the cylinder and you want to fix that before installing another piston. Jon

1. Your frame is a 1993 if the VIN corresponds. The hydraulic clutch was introduced in the GT32 model in 1992. 2. We don't know without further information if, in fact, a later model engine has been installed. 3. You should be able to get gaskets for your model. Jon

Be sure you take the carb completely apart, not just blow things out, especially the float needle assembly. Sounds like something to do with the main jet as it dies just about the time the carb starts to draw from the main/needle jet system, although you said you cleaned that all out. Also look for any binding of the floats movement in the bowl. Jon

My guess is that we're actually in agreement. My recc' for 1/6 is for no weight on the bars so that the peg weight only is the static setting (which is the most consistant and repeatable setting) and when in riding mode (with weight on the bars) it should be in the 1/3rd range. I don't think we specified rider position when measuring race sag. Jon