thats_a_five

Check that the baffle in the silencer is not plugged. That will choke up even the best running bike.

Ben, search this forum back within the last year. There was a thread about a very similar looking crack right along the weld. I don't recall the final conclusion, sorry. You already got good advice about checking with the dealer or importer.

Its better to have the fan on all the time rather than to not come on at all. If you are going to ride before it is completely fixed, wire it on the "On" position.

The middle section and the silencer section are assembled to each other in a slip fit. If you look inside the tube, you can see 2 grooves for O-rings. There should be red O-rings (usually high temperature compound, not cheap black O-rings) in each of those grooves. You can also seal the joint with some high temp silicone seal. Looking at the pics, I see 2 problems. 1) the tube needs to be welded to the housing. 2) the mounting tab has a crack that also needs to be welded. Find a good welder, take the bike there so the parts can be aligned correctly for welding.

US$3650 is way too much for a '94 Gasgas. I only paid about US$1200 for mine 6 years ago. I just picked up a 2005 Montesa so am planning to sell mine in the US$1000 range. If you can afford the EVO, that is a much better value for your money. Have fun. Keep your feet up!

That is a 1994 Contact JT25. I have one just like it. Great bike, very rugged and reliable. Not as light or responsive as the "Pro" models but a great learning bike. 2 common issues are: 1) the seal in the water pump goes bad and coolant gets into the gearbox. Seal replacement is a relatively easy job. You can tell by pouring a little of the trans fluid out. If it is milky looking, it has water and should be drained and refilled with fresh ATF, and coolant added to the radiator. 2) the cast subframe (holds the rear fender in place) breaks if hit too hard. Hard to repair. If you have metal working skills, a replacement can be made out of aluminum plate and bar. The rear tire in the pic looks to be pretty worn. It would be OK for practice but for real trials, I would want a newer tire. Have fun!

Good that you may be able to adapt a kicker from a different bike. You said the water system was dry. I would recommend to drain then trans oil first and check for water. The water pump seals often fail and the water end up in the trans. Water is not a very good lubricant so get it out and replace with ATF. No doubt the carb needs a complete teardown and cleaning. Once you get the kicker fixed, pull the plug and check for spark. If there is spark, re-install the plug, add some fuel, BUT, before you try to start it, get the bike on a stand with the back tire off the ground. Clutches often stick to the plates when they sit for a while. If it starts with the tire on the ground, you may be in for a thrill ride with no way to stop. Oh, and make sure the kill switch is wired up correctly.

Which part of the kick starter is broken? The shaft coming through the side cover or the arm that comes up from the pivot outside the cover (kick lever)? If it is just the kick lever, I would look to change that and not have to risk getting the shaft and seal to work correctly from a different bike. If you are going to alter the shaft and side cover, I hope you are a good machinist.

There are two ignition timing curves. One for dry one for wet. Dry is a little more explosive, wet setting is a little less so.

I run tubeless on my modern bike and the hand-me-downs get used on the TY.

I recall a thread here a while ago about this. What I recall is that the IRC tires have a slightly larger inside diameter then the Michelin. As a result the IRC tires come off the beads on some tube type rims unless they are run with more pressure. I have an IRC with a tube and rim lock on my '74 TY250 that I run at about 11 PSI and have never had the bead come off. I don't compete with that bike, it's just a play bike for me and a buddy bike for new riders to learn on so the higher pressure is not an issue.

I don't know specifics on your bike, but most shift shafts are made from soft steel so straightening is OK. Usually can be done without heat, using a flat anvil and a couple thumps with a 2 pound sledge hammer.

You say "where the power doesn't kick in for almost a half turn of the throttle." Check the free play in the cable. If the cable has too much slack, the carburetor will not open when it should. This will also result in the engine not being able to rev up as high as it should. Net result not much power. My '94 JT25 (250) has a 10 tooth front and it also revs out so I ride many sections in second. Of course, the 250 has more torque than your bike.

Wow, sorry to hear that. I don't know about where you are, but in USA you can send your bad barrel and get a redone barrel and piston on an exchange program. Cheaper than buying all new.

I changed my front to 11 tooth. It is still a bit high for real trials riding but I do still ride it on the street a little. This is a great forum, many helpful people so ask your questions here. I know there used to be a club in NW Connecticut - I think there is still one in Rhode Island.

A few seconds at high RPM should not damage the engine. Watch some of the pro riders clean theirs out before a big splatter - they rev to the moon. If the bike was upside down when you shut it off, some water may have run from the exhaust into the cylinder. This in itself should not be a big problem. If the O-rings were in good condition and in the proper grooves, the chance of getting coolant into the piston is quite limited. I would be concerned about the low compression. Get the jug off and look very closely at the rings and the ring grooves in the piston. I fractured ring might have broken a piece of the piston off.

Good to hear that you got it running. Keep your feet up!

Coolant Leak Water will always drip down so the leak could be up higher, just running down and dripping off the bottom of the engine. The sequence that you install the hoses should not matter. Were the hoses new or did you reuse the old ones? Reuse is OK – just make a habit of inspecting them for wear from rubbing or age cracks or splits. Check that the hose clamps are tight. How big was the puddle on the floor? Every time I top up the radiator on my bike it will spit some out the next time I run it. Not much but it was concerning until I collected and measured the amount. About 1 spoon full, so I stopped worrying and now only top it up every couple months. If you use colored coolant, you should be able to see where the leak is. Fill the rad, run the bike up to temp, shut it off and watch as it cools. Use the paper trick to follow the drip up to its source.

Choking What year is your bike? The rear silencer has changed over the years. You removed just the rear silencer, right? You can run the bike without it to test. It will be loud but if it revs freely you will know the plugged exhaust is the problem. My bike is a “TXT Edition” not a “Pro” so my silencer is different although the basic principles are the same. To clean it, you have to remove the rear cap. I had to drill out 4 rivets, yours may be held on with bolts. Take off the cap and look for a metal screen. It is probably very plugged with black, oily soot. Soak the screen in solvent (petrol, diesel fuel or parts cleaner – no smoking!) then scrub with a wire brush until you can see through the mesh of the screen. There is a perforated metal pipe that goes through the silencer to the inlet. This pipe is surrounded by “packing” that quiets the noise. This packing is probably also pretty saturated and the holes in the perf pipe may also be plugged with soot. I would clean the pipe and replace the packing while you have it apart, although these will not cause the choking, just the plugged screen will do that.

If you make the change from a 300 jug and piston to a 250 set, how will the insurance people know that the bike is now a 250? If they look at the serial number of the bike or motor, it will still indicate 300. I would hate to see you go to a lot of work and expense and then the insurance people still say it is a 300 based on the serial number. Maybe they will just look at the bike. In that case, you don't need new jug and piston, you just need new plastics.

Coolant Leak. The cooling systems on Gassers are pretty simple. Radiator, cap, hoses, hose nipples, water pump, thermoswitch and head o-rings are all there are to leak. If the leak is not visually dripping, you can use paper to help find it. You can use newsprint, paper towels or even toilet tissue. Refill the system with water, dry off any spillage, then push the edges of the paper against any place that might be leaking. A little water will be very visible as the paper soaks in the water. White exhaust smoke Is the white stuff smoke or steam? Steam will disappear quickly while smoke will hang around longer. If you use anti-freeze in your radiator and it is steam, you will smell a very sweet odor. 99% chance that would be from bad o-rings under the head. If it looks and smells like 2 stroke oil burning, it is most likely a plugged exhaust baffle or spark arrestor. Those are usually located on or in the end of the exhaust system. This will cause smoking and choking of the engine. Remove and clean the screen. Good luck. Let us know how you get on.

If you are not going to strip it down I would not suggest sand or bead blasting because of the risk of forcing abrasives past the seals. You could use heat or chemicals but I would pull the engine out of the frame to be able to get at the surfaces well. Heat with a scraper and wire brush works good but be careful to keep it away from anywhere there is a rubber seal or gasket. Chemical strip will remove most paints pretty well. Make sure you rinse it off very well because most chemical strippers are pretty alkaline. Aluminum and alkaline do not get along very well. The key to good paint adhesion is clean, clean, clean surfaces. Any oil on the surfaces is bad, WD40 or silicone oil is the worst! Stop by your local auto paint shop and they can recommend some solvents. For the lower end, most good quality spray paints will be OK. Auto parts shops usually carry engine paint in rattle cans. It is pretty good paint and comes in different colors. For the fins it would be good to use high temperature paint.

FIns - I have never used araldite: I understand it a filled epoxy resin type adhesive. I would not recommend using it on the fins. Materials expand and contract with heat. Metals and plastics have different expension and contraction rates, so I would be concerned about the materials eventually coming apart. My recommendation is welding. Paint stripping and repaint. There are three primary ways to strip paint, heat, chemicals and sand or bead blasting. What are you planning to strip? Just the fins? The cases? Are you planning to disassemble the engine from the frame? What level of painting are you looking for? Show quality, or rattle can?

Measure the inside diameter of the bars to be sure you order the right size bar ends.

Many trials riders install bar ends that prevent the throttle from getting jammed like that. I ran them for several years and have recently changed to "bark busters" and I like them. Bark busters protect my hands when I misjudge a tree along the trail, they prevent the bars from driving so deep into the ground (jamming the throttle tube) when I fall, and they also protect my levers from breakage. All good things. Keep your feet up and the rubber side down.