jse

I'm not sure how the 250's are set up but from what I understand, the switch is essentially an on/off switch to toggle the CDI maps. The larger 05' models came with the two-mapping system but no switch here in the States. There were two wires under the front of the fuel tank (orange/black) and you could plug/unplug them to get the two maps. It was easy to add the 06' switch by just plugging it into the wires and mount it on the bars. You should expect a slight decrease in top end with the longer pipe but you should also see an increase in torque in the lower RPMs. Torque does the work and once you adapt to the change, the bike should be, in most cases, easier to ride. Jon

Good point. Altered noise level is often mistaken for power delievery characteristics (just ask a Harley guy). Head pipe changes often require jetting changes to achieve peak performance. A longer head pipe, in comparison to the one it replaces, creates longer wavelength pulses which tend to shift power output lower in the RPM range (all other things being equal). You might try a needle height adjustment to start with (always start rich and then try lower) as the pipe usually will affect the area monitored by the needle profile the most. Jon

Awwww, thanks. I find this forum quite valuable and I'm sure that others (like PeterB, for example, who has given me a lot of good pointers) will agree that being able to tap into the collective knowledge of riders from all over the world at the click of a computer key a really neat thing! Jon

Peter has a valid point and I could see where the aerated trans fluid might skew the air/fuel ratio. My Pro fan cycles on fairly constantly on warm/hot days and there have never been signs of engine overheating, so I'm assuming your condition is normal. As Peter says, the fan should blow fairly strongly and you'll hear it with a helmet on. "pinking", ah, yes, my internal spellcheck was on the fritz. Here in the States we call it "pinging", supposedly an "onomatopoeia", words that sound like what they are describing, but "ping" is not what it really sounds like to me. I guess it's a cultural/language thing. A friend in Japan assures me that cats absolutely do not "meow" in Japan, they do, however, "murr"....... Jon

Jan, Clint Eastwood, in one of his "Dirty Harry" films had a famous phrase that seems to apply here, "Well, how lucky do you feel?" Keeping the fluids up could buy you a little time and quite possibly no engine damage, but, in reality, Trials engines are built for competition and in competition we often push them more than we mean to, so given the choice, I'd opt to fix the problem as soon as you can just to be safe. The bigger jet and needle adjustment (by lowering combustion chamber temp and modifying flame front behavior) would address the symptom, but not the disease, if it is, in fact, carbon build-up and it would still be there. Let us know what you find. We're all just making educated/experienced guesses based on words on a computer screen, so any feedback will help us in the future. If it's your first time inside a Pro engine, you'll find it very interesting.... Cheers and good luck! Jon

The first won't fit, but the number plate type might be easily adapted, although it would probably make the steering very "heavy" when full. As I remember, before the Pampera used a different frame, it had a larger tank that fit the Trials model (see: http://www.gasgasmuseum.com/1994-1997gasga...sgaspampera.htm ), although the tank/seat assembly junction might need to be modified to fit, just a thought. Jon

Jan, I think that maybe the dealer was incorrect in the diagnosis. The Pro will not likely run "lean" if the crank seals are leaking as the inside seals are not exposed to "outside" air, but to transmission fluid on both sides. The knocking is probably a buildup of carbon in the combustion chamber caused by incomplete burning of the tranny fluid, thus raising the secondary compression ratio beyond the octane rating of the fuel and causing the "plinking", as the English say. I'd fix it as soon as possible as it will only get progressively worse and a reduction of lubricating fluid in any transmission is dangerous, especially in the Pro as the crank bearings are also lubricated by the same fluid. Jon

Alright, Mark! I just saw this and the next time we're at a Trial and you whine at me, yet again, "Joooooooon...which one is the brake and which one is the clutch?", I'm going to let you figure it out for yourself! Jon

Steve, Check the "starter jet" in the carb, which is on the brass tower with the o-ring. Some Pros came with a #60 (.6mm, a little lean for the starting circuit) and I've drilled mine out to approximately a #80 by using a .031" drill which has helped my engine usually start 2nd kick in any weather (I also have an 02' 280 Pro). The reason you normally don't want to open the throttle when using the "choke" is that the starter circuit is a seperate venturi, using the starter jet, and if the slide is up, air will not be drawn into the starter venturi and extra fuel will not pass through the starter jet. Be aware that you have a magnesium engine and sidecover so you want to use only distilled water (as you should with any alloy engine). Some riders use straight anti-freeze with good results. With the newer CDI systems, as opposed to say, the early MotoPlat, I've found they are more prone to just shut down, ie work well or not at all, when trouble occurs rather than deteriorate in performance (provided that the malfunction is internal and not grounding, frayed wires etc). You also might want to check your reeds (from what you describe, they have 6 years of hard use) and re-seal the manifold and reedblock in the process. Jon

I've not had to bleed the system in the Pro as there don't seem to be any major high spots that would trap a bubble upon refilling. If you fill the coolant up to the top of the filler neck, a little coolant will dribble out the overflow when the fluid normally expands and some riders mistake this is a sign of overheating. I always like to re-check the coolant level after running the engine a short time whenever I start with an empty cooling system (let it cool down and if necessary add coolant just to the bottom of the filler neck). Due to the two "sets" of slots on the primary crank gear, the waterpump shaft pin can go in two ways. If the pin has not aligned with the gear slots, the cover will not fit flush with the case at the front (if the pump is attached to the sidecover upon re-assembly). If the shaft pin has not gone down into the gear slot, forcing the cover on will most likely cause some damage. I try to never force things when assembling engines as I've found that when parts do not fit together with normal pressure, they are usually trying to tell me something, and ignoring their pleas is usually an expensive process. To align the pin with the gear slots I like to use the lower waterpump screw holes (the one that takes the slightly longer pump mounting capscrew) as a reference. I align the crank gear slot with the bottom W/P mount hole in the sidecover and then turn the shaft on the pump so the pin aligns with the lower mount hole on the pump body, add a little grease to the thin o-ring and it usually slide in with no problem. Jon

It's a possibility, if vibration was the base cause to begin with. Modern carbs with Viton tipped float needles are a little less prone to overflow due to vibration. If the carb float bowl rests on the engine case (or the carb body contacts metal around it) engine/frame harmonics can cause vibration and frothing in the bowl, resulting in aeration. Keihins have a slightly lower hanging bowl than the Dellorto, so it's something that needs watching. Some of the earlier TXT models (97 JTX320, I think, for example) used an extra reedblock spacer (maybe 4 mm thick?) and this wedge spacer looks exactly like one of those that was set on a belt sander and what would have been the "top" part had pressure put on it so that part ended up about 2mm thick. An extra spacer gasket and slightly longer screws were used to mount the wedge in between the reedblock and manifold. The wedge would tilt the carb up a few more degrees and raise the carb body up a couple of mm's due to the added length of the manifold reedblock assembly. Jon

Steve, As far as I know, a short stint with vinegar should be o.k., I haven't tried it myself but my chemist buddy says that a normal 5% acetic acid dulution of vinegar (or ethanoic acid, glacial acetic acid, ethylic acid, methanecarboxylic acid or vinegar acid and it's also known) should be safe as long as it's not left in contact with the aluminum for any length of time. Let us know how it works. I know the malty stuff goes well with chips....... Jon

A small wedge shaped reedblock spacer is also available from GasGas but I don't have the part number right at hand. Fit between the reedblock and manifold with the thick part at the bottom, it tilts the manifold slightly upwards enough to raise the carb angle to prevent fuel frothing in the bowl due to engine vibration. Jon

My last bike was a 1996 JTR370 (it's actually a 338cc engine, despite the "370cc" cast in the cylinder base). Your son's bike has the Ducati ignition and no points to re-set. Make sure you have fresh premix in both the carb and tank. If it's been stored for any length of time, the high-end aromatics boil out of the vent and they aid starting. Use the "choke" lever at the top of the carb (straight up is on) and do not touch the throttle when kicking it over. Use body weight rather than leg muscle, this is a high-compression monster and just jabbing at it with your boot will only make it mad. http://www.trialspartsusa.com/tech.html is a website with a lot of good info on it. You can use the 2001 parts manual as it is essentially the same basic engine. Jon

Just a guess, but make sure the loop on the return spring that sticks out is indexed to the proper machined hole in the sidecover. Also, there is a thin machined washer that fits on the kickstart shaft, before attaching the sidecover, and 9 times out of 10, it will stick to the inside of the cover when removing it and then fall off and get lost as it also has a knack to fall off in the area of the ground where it will be the most difficult for it to be found..... Jon

I understand it's a DOT mandated safety feature to prevent motorists from even thinking about following too closely..... Jon

It's a standard right-hand thread with a plastic washer. You can use a sharp centerpunch towards the outside part of the bushing and coax it out. Be aware that there is a thin washer on the shaft you don't want to lose in the turbine blades. Keep exact track of the capscrews when taking them out as they are different lengths and go in certain places on the sidecover. Don't just slap it back on but carefully align the pin on the waterpump shaft with the slots on the crank gear. Check out: http://d-mis-web.ana.bris.ac.uk/personal/H...f/media/gasgas/ before you do any work on the Pro engine, it's a quite different engine than any other and can be easily damaged by a lack of knowledge. Jon

That's what the factory spec.'s are that GasGas sent to me, so it will be light and less then half a kilo more than what my 02' mag engined Pro weighs. I'm not exactly sure what the criteria for measurements are and they depend on the marketing angle. "dry weight" in past other brand releases have been exactly that, no oil or coolant of any kind, including in suspension components but I would imagine that GasGas is more prone to release "running weight", which usually means no fuel, but otherwise containing the appropriate oils and coolant. Can't wait till mine gets here..... Jon

From what you describe, the seeping is a result of a malfunctioning clutch cover gasket and replacing it will solve the problem. Jon

Actually, I have an 02' 280 Pro as my personal bike and with a couple of updates, it's been great. I like the 02' handling and lightness (the 02' has the Magnesium engine, like the Raga, 03' on up are aluminum). The nice thing about the Pro is that just about all updated parts retrofit the earlier models. I could probably have a new bike if I wanted (actually I have my order in for one of the new 4T's when they get over to this side of the pond) but I tend to develop a close, personal relationship with my bikes and hate to give them up. A "quick and dirty" way to check the straightness of the shifting forks is to put them back-to-back on a shaft and rotate them back and forth. The fingers should slide past each other closely and easily, if they scrape or there is a gap between the fingers they are most likely bent. The usual way to check forks is to look very carefully at the wear pattern on the tips, it should be even. If it's worn on one side or other of the flat surface that contacts the collar, it's bent. The sure giveaway is that if there are slight contact marks at the bottom of the "U", between the fingers, the collar has been scraping there. The forks are a really tight fit, with little clearance, in the shifting collar ring, so any misalignment usually shows up as contact marks. Jon ps. Thanks for all your posts, PeterB, I always learn something extra from them.

A hint to help keep the tube contour consistant is to wrap the sandpaper on a piece of bar stock or other hard, machined, flat piece of metal and sand around the tube (not in just one spot) rather than lengthwise, kinda like the same reason to use a sanding block rather than fingers. The level sandpaper surface will smooth down just the high ridges rather than make a depression. I've used SuperGlue with good results and the tubes are fine after several years of use on my TY. Jon

Generally, the clutch should be fairly easy to bleed (unlike rear brake systems, yipes!). The color of the top of the clutch reservoir and the writing on it will tell you what to use (unless a previous owner switched to DOT-5-Silicone, for instance)-black will be DOT3 or 4 and green will be mineral oil (not the drug store kind but a fluid just made for clutches). If you have the servo cylinder off, you'll want to fill it with fluid before installing it on the sidecover post (known as "bench bleeding") as a bubble usually gets trapped there due to the "step" where the post ends and a pocket exists. Then using a fluid filled syringe to pressure bleed from the bleed fitting on the sidecover upwards gets most of the air out. If the lever still feels a little "spongy" there are generally three places where bubbles hide: (1) the servo cylinder pocket mentioned above and laying the bike on the left side and working the lever will usually push the bubble up into the post bore and then into the second hiding place. (2) The bleed fitting, where using lever pressure and cracking the 7mm bleed bolt will usually get that out or up in the system to #3. (3)The loop in the line after it leaves the master cylinder. Turn the bars so the M/C is at a high spot and lightly work the lever to force the bubble to rise up into the reservoir. Jon

Steve, I don't know what the "max" serviceable life would be in terms of end gap but I would guess that at 2 or 3 times starting end gap (.6mm-.024" or .9mm-.035" for instance) the ring would have lost a fair amount of wall contact tension and you would be giving away some low RPM power. This is just a guess and I've seen some engines with a surprizingly wide end gap run fine and others with a fairly tight gap lose some compression. Trials engines are a funny animal and sometimes seat-of-the-pants analysis works better than a caliper. I like to use a thin, fine grit stone rather than a file to dress the end gap, it takes off less at a swipe (easier to not go overboard) and leaves a better finish. If you want to do it the scientific way, after proper break-in, take a compression reading (plug out and grounded and throttle WFO) and record that number. When in checking it later, you might want to look at replacing rings when compression drops off 15% of that number if you want to keep the engine in top notch shape. Most of us go a little past that point till our seat-of-the-pants gauge tells us somethings off, but that's how you would maintain a Pro's engine. Cheers. Jon

Steve, As your bore is about 2.86", I'd probably opt for a little more clearance, maybe a little less than .3mm. As can be the case, my eyes glazed over a little when I quickly proofed my post on how to measure ring end gap (we have two Nitromethane-powered 10 year old twin Grandkids visiting for a couple of weeks) and I left off a decimal point. The free ring should be down about .15mm from the top of the bore when measuring gap, or you can use the bottom most part of the bore where the circular lining is continous (no ports). The idea is that you want to measure the gap at a point in the cylinder where it will be the closest, which will be an area that will have the least wear or "taper", the very top or very bottom. It's not such a critical thing in a Nikasil lined cylinder as the taper is usual minimal (pistons wear faster than cylinders, normally) but you want to be as accurate as possible when taking any engine measurements. The idea behind using a "Dykes" top ring is that exhaust pressure acts to push the ring out against the cylinder wall, helping sealing. They are usually too heavy and have too much drag for high-speed engines like roadracers, but work really well in under 10K RPM two-strokes. Jon