thats_a_five

The engine was basically the same from 1994 to 1998. There were different capacities 125, 250, 270, 321 over the years.

Wow, what a gorgeous bike. It reminds me of when I had a '94 and my riding buddy had a '95. Probably the best trail (trail, not trial) riding bike I ever owned. Also a good trials bike. Jordi Tarrres won some world championships on them. 50:1 is too much oil but OK for break-in use. After 1 or 2 tanks, switch to 80:1. Keep your eye on the transmission fluid. Those motors had common water pump seal failures that leaked coolant into the trans. If the fluid gets milky, there is coolant leaking. The wire you mentioned is the signal wire for the small electronic readout located just behind the fuel fill cap. I have never seen one that actually worked. I have a parts manual and electrical diagram I will try to attach. Parts manual is about 8 megs. I have to agree with Oni Nou. That bike is too nice to actually ride. Know that being new to trials, you WILL drop the bike, scratching the paint, denting parts, etc. The bike will never look that new again if you ride it. I strongly recommend you see about trading,or selling, it to someone who wants a museum piece. Then go get a newer bike that already has been ridden. Don't misunderstand, I DO want you to ride trials. It is a blast! I just would hate to see such a perfect piece get damaged. Take it to the local GasGas dealer, the local club events, post it on CL. You might be surprised at what you get offered. 1995_Trial_JT25_Parts_Manual.pdf

I am not exactly clear what you mean by " feels like it needs a good clean " but there are only a few moving parts so here is a rundown of what is possible: 1) remove the lever,clean all pivot points, lube and reassemble. 2) Bleed the hydraulic system as suggested by Maxwell Smart. 3) Clean the friction plates inside the clutch. Remove the side cover, remove the 6 screws and take out the pressure plate, steel plates and the discs with friction material. Clean thoroughly, lube with transmission oil and reassemble in the same sequence of disassembly. Probably a good idea to change the transmission fluid while you are in there. Make sure you know what fluid you plan to use before taking things apart. Montesa recommends a special oil.

I removed the metal heat guard, then wrapped my pipe with header wrap. Stainless steel wire wrap to hold in place. Reinstalled the sheet metal guard. Haven't melted any pants since.

Hey Dan, that’s not fat, it is “traction enhancing body mass.” For all you youngsters posting, here is a link to video of one of our club members, Bill Thompson, who not only competes at the USA National level, but wins in his “over 80” class. He has been an inspiration to me and I hope he will inspire others. Truly a great man.

How does your spark plug look when the bike acts up? I have been noticing my plug getting sooty, black more and more. Cleaning the plug or changing the plug fixes the running problem. First I noticed that when the air filter got dirty, the plug would foul as described. New filter, very lightly oiled helped. Recently it has been getting harder to start and the plug is fouling when letting the bike warm up at idle. I have heard that this could indicate the valves need adjustment. I have not had time to do so. Once the bike gets warm and with a clean plug, it runs great.

As far as I know, USA GG's did not have turn signals. Therefor, no need for a flasher. I do recall recently seeing an add for a flasher with adjustable flash rate that is intended for using LED lights in vehicles that originally came with incandescent bulbs. I think it was on eBay. Perhaps they will meet your needs. Good luck.

That plug looks pretty good, maybe a tad lean as mentioned by Scot_Taco. The carb has 2 screws. One is idle speed, other is idle mixture. Idle speed screw is central to the slide bore, mixture screw is offset and usually smaller head size. Adjusting the mixture screw out and it will richen the mixture but mostly at idle - minor effect at higher speeds. Other ways to richen the mixture are to adjust the little needle in the slide up (put the clip one groove lower - beware those little 'C" clips are tiny and always try to fly off into the nether regions of your shop). It is counter-intuitive but reducing the oil percent will richen the mixture but I wouldn't go less that 50:1. Regarding upgrades versus original, I have to ask about how aggressively you ride. Reason is, many of those original parts (Tank, headlight rim and bucket, switches) which look really pristine on your bike are worth big money as spares. Ride aggressively you are likely to drop the bike, damaging those and reducing their value significantly. So you might want to consider looking around for some used parts or upgrades, so you can take the pretty parts off and keep them pristine. If the shocks are OEM, they might be sacked out and upgrades might be worth it. You might want to take a look at Bob Ginder's site B&J Racing. He has some cool info and stuff for TY's. Enjoy!

1-2-3-4 While you have the tires off, may I suggest a couple things? Check the wheel bearings. If your current rear tire holds air well, do not remove the rim strip. They can be a P.I.T.A. to reseal. If you do remove the rim strip, put a drop of oil in each of the spoke nipples and see if you can loosen and retighten them. Better to keep them working then have them corrode to the point they are seized. If you replace the rim strip on the rear, the ones with the molded in nipple are easier to seal. Also, the new tubeless rear tire can be very difficult to mount and get the beads to set. A lot of guys use soapy water to help the rubber to slip on the metal rim. I do not recommend that because soap is alkaline. Alkaline loves to eat (corrode) aluminum. I use a real tire mounting lube but a little vegetable oil can help. Also, a warm tire mounts easier than cold (set them out in the sun for a couple hours first.

JonV8, true that many people have switched to pre-mix. Like you, I can't tell from the pic if the cable is still in place but I think I can see the hose from the pump to the cylinder which is why I brought it up. Between us, hopefully JohnnyJazz learned more about his bike and can make good decisions. FYI, my '74 TY250A still runs the oil injection pump. That way I only have one fuel can for all the bikes. Cheers!

I had a similar situation with a previous bike. This may help you diagnose your bike. After doing a water pump change and some other maintenance I went riding and after a while and noticed steam coming from the radiator overflow tube. Rechecked my work – all looked OK. Topped up radiator and next time riding, same steam. To learn how much was escaping, I zip-tied a small plastic bottle to the frame and ran the radiator overflow tube into the bottle. Rode the bike and it spit 5 – 10 cc’s into the bottle once hot. If I topped up the radiator, it would spit the same amount. If I didn’t top up it would not spit any. Conclusion: The cooling system needs a little air space in the radiator to allow for normal heat expansion of the coolant. Bike never overheated but if I overfilled, the bike would spit the excess. Removed the bottle and relaxed, knowing there was no real problem. I hope this helps you.

One more comment. FeetUpFun is correct that screaming the bike for long road runs will cause the top end to get hotter than desired. Increasing the main jet will allow more fuel which will help cool it. On the other hand, adding more fuel will reduce the relative amount of oil being injected (assuming you are still using the automatic oiling system) which will affect the lubrication of the bottom end. So it is a trade-off depending on how you will be riding the bike. A way to check: After riding on the roads back home, shut the bike off, let it cool a bit (so you don’t have to deal with hot pipes and plugs) remove the plug and inspect the ceramic insulator by the spark tip. Bright white = too lean. Would benefit from bigger jet for more fuel and cooling Black and oily = too rich. Would benefit from smaller jet. Light tan = Perfect. Do yourself a favor and always carry a spare plug and wrench to change it. Even well jetted bikes will foul plugs from time to time (usually at a very inconvenient time). Spare plug and you are back riding in 5 minutes. No spare plug and you are pushing the bike 20 to 45 minutes for 2-3 miles. Not fun.

Hi JohnnyJazz. That is a very pretty bike. If you did the restore, great job! A couple thoughts, facts, and questions. Words in italics below are from your posts. August 8. I only want to potter around the back streets of Brooklyn where the average street speed is 25-35 mph getting to some off road places I know to practice trials. Sept 8 . . . have found with the current gearing of 12/53 I really am struggling to keep up with traffic even on slower roads. let me state that I am well aware this isn't a road bike and isn't geared as such and I am not a speed freak at all, I’d just like to not be a hazard to others! I’m only riding 2-3 miles to get to a few industrial construction sites where I can practice trials. . . . . . I find with the 12/53 I am lucky to get maybe 35 mph tops and if my sums are correct the difference between a 12 and a 14 front is 16.9% so that's nowhere near 60! The bike seems to be running very well, a lot of torque and smooth but just as slow as a steam roller. . . According to the Yamaha ad material for the 1974 TY250, it has a top speed of 100 kph (62 mph) with 14/53 final gearing. Going to 12/53 is 14% reduction (14-12, divided by 14) which should net you a top speed of 51.6 mph at redline (Yamaha did not post how many rpm that is but max torque is 15.2 Ft# at 5500 RPM so it should turn at least 5500). First question: Are you getting into 5th gear? Fifth gear is a 0.656 overdrive, where 4th gear is 1.0. Fifth to 4th is about a 48% reduction which would net you top speed of about 32 mph. Second question: Are you getting full opening of the slide in the carb? If not, you will not get max power or rpm from the engine resulting in lower top speed. Solution could be a simple as a throttle cable adjustment. Meanwhile: Learn to use that rear view mirror and move right to let faster vehicles pass. At most it will delay your arrival to your riding location by a couple minutes. Riding in and around Manhattan, you are probably spending more time than that sitting at stoplights. Learn to pull away from lights in second or even third gear. That will get you up to speed faster so less bothersome to cars behind you. Observations: It looks like your levers are located fully out toward the ends of the bars. You might try moving them further in toward the center of the bike. This will increase the leverage you have on the clutch and brake, while also reducing the chance of breakage if/when the bike falls over. Is that a bulb horn I see in the picture just above the fuel cap? It brings back decades old memories since I had one on my bike. I suggest relocating it so you can honk it with your thumb without having to take your hand off the grips. If you need to honk, you will probably also need to work the clutch, brake and or throttle at the same time while hanging onto the bars with both hands. Have fun!

Check to see if your throttle cable has moved down and is being hit by the radiator fan.

That is great to hear it just needed a good cleaning of the carb. A five hour ride is always a good day. And certainly a good test that all is well with the bike. Have fun!

Problems like this rarely fix themselves overnight sitting in the shed. No disrespect intended but are you sure the shop knows what they are dealing with? Look under the engine and see if the bash plate is bent up against engine. There should be some space (maybe a rubber pad to absorb some of the impact). Pull off the bash plate and look for any signs of damage, such as cracks, bent housings or unusual gaps in the gasket surfaces. While reading the description, my thinking was, either: the crankcases got cracked or broken, allowing air to leak in, and moving some parts inside the transmission (thereby preventing shifting into 5th and 6th gears) and something inside the clutch cover was hitting the clutch basket, or the broken case was being hit by the crankshaft as it turned. OR, the shift shaft took a major hit, damaging the seal on the shaft and breaking parts in the shift lever inside the clutch cover. OR some combination of these. I strongly recommend you to have another knowledgeable person to make a thorough inspection of the underside of the bike and check inside the clutch cover before you ride it again. Broken pieces inside are expensive but if they are allowed to move around they damage other parts and the repair cost goes up exponentially. I hope I am wrong and it was just your imagination. To me, spending another $50 to have it checked is a great investment to avoid creating a $1000 fix in the future. Good luck.

Generally 2 stokes don't have super hot exhaust but on long uphill pulls they will definitely burn off the excess oil. Here is a thought. If you can find another rider with the same model, pick up one of the electronic non-contact thermometers, ride up a long hill and compare the temps of the two exhaust systems. It might even work with a couple cheap oven thermometers, hose clamped to the muffler. One thing I like to have when solving problems is data. Glad to hear you fixed the vacuum leak.

It seems that you have the mechanical skills, why not fix the vacuum leak at the reed block? You know it creates a lean mixture which makes 2strokes run very hot. Also, do you want to risk unfiltered air getting directly into your motor? It sounds like your pipe is burning off excess oil during uphill pulls. This is fairly common with trials bikes due to a lot of slow running. Oil builds up then burns off during hot running. Do you have a spark arrestor or other screen that might be clogged? You also might need to clean out and repack your silencer.

I am not an expert on your bike but I think that is a weep hole designed in. When the water pump seal fails, the weep hole leaks the water outside the case rather than have it just leak into the transmission. It also helps you know there is a problem before it becomes a big problem. Huski's post above is exactly correct.

Things you can say about your video game console, but not your girlfriend. Boy, this thing has a lot of memory Keeps getting real hot and going down on me. So what if its 11 years old! 4 people can use it at the same time It never works, I have to input everything oh, that was easy to turn on I can play with it whenever I want. I wish this piece of **** would work Wow! This only costs $60 a year. I'm bored. Time to get some new content Oh boy, there's a mute button. i need to blow her to get her working that has a shiny box Next year I'm totally upgrading to the new model for better graphics and an overall more enjoyable experience. I had to line up for hours to get one So light I can carry it around. I lent it to a friend I'm taking this back to the store. I would like a system that's a bit younger. I could play with this for hours. I feel a sense of satisfaction when I beat things on it. I can turn it off when it over heats and stops working I feel satisfied after playing with you. The piece of **** is too big and hardly even runs anymore.

Here is the link to the thread started by Zippy. It has some pretty good information about what can be causing these issues.

Gotta agree with Zippy on this one. Looks like it has been ridden and could use some love. Bent rim might be repairable if you are skilled with a torch and press or even a mallet. If you ride serious enduro you probably have experience with this sort of damage. Worst case if you try to repair is that you crack it and need to replace the rim restring the spokes. Not uncommon for spoke nipples to have corroded and seized to the spokes and you need a new set of spokes and the skill to restring the wheel. Take a look into the sight glass by the kicker. If it is milky, there is water getting into the trans fluid. Common cause is failure of water pump seal. Easy fix, just do the seal and shaft at the same time. There are 2 throttle tubes available, fast is black plastic, slow is white plastic. Pull the grip away a little and you can see which is installed. If the bike is too “quirky and twirky” you might want to use the slower throttle tube. Hard to see in the picture but looks like the tip is broken from the clutch lever. Get a spare set of levers. You will need them. Ride it and have fun. Be advised that many of the things you learned to help you go fast will need to be un-learned so you can go slow. Most important: Have fun.

Based on this info, it seems logical to conclude that the problem is associated with air intake, not the carb or exhaust or timing. I just looked at my ’74 and confirmed my memory that the air get into the airbox through 2 holes on the left side of the box. These are behind the oil reservoir. If they are completely blocked, the bike will not run. If they are partially blocked, the bike could run at low RPM but not get enough air to run faster. I suspect that something happened to the airbox or the oil tank leaving too small a space for air to get to those intake holes. Good luck. Let us know what you find out.

Interesting read. Thanks. You got my curiosity up so I have been thinking and reading about bearings for a few minutes. What I have learned there is a difference in failures between bearings in a relatively clean environment and bearings that get submerged in water frequently. Bearings in clean environments fail mainly from high vibration due to out of balance equipment or loss of lubrication (either not enough or too much grease as described in your article). Bearings that go in and out of water regularly fail due to water causing corrosion of the bearing surfaces. I excerpt some info from the “Bearing Buddy” site. “The hubs on a boat trailer can heat up during long trips and when they are dipped into cool lake water, the sudden temperature change creates a vacuum inside the hub. This vacuum will draw any condensation, moisture, or impurities directly into the bearings, which can cause premature bearing failure.” I think this could be more like the bearings on a trials bike. They get heated when riding and applying the brakes. Then dipped in a stream or even being washed with a stream of cold water from the garden hose or pressure washer will create that vacuum, sucking water into the bearing, leading to corrosion and bearing failure. Regardless how the bearings fail, I think the message is clear. Check them periodically, at least yearly. Pop the wheel off the bike, stick your finger into the inner bearing race and see if it turns smoothly. If it is stiff or rough feeling, replace it. A few minutes in the shop will keep you and your bike happy in the field. Cheers all!

I am glad to hear you have solved the problem. From what you described, I can imagine the bearings were getting very hot as you rode. That heat would transfer to the disc and ultimately to the brake pads and caliper. That heating and cooling would lead to expansion and erratic brake performance. So, did you pack those new bearings with grease before you installed them? Factories put minimal grease in when they assemble bearings. A good packing will not only lube the moving surfaces but also prevent water from getting to the bearing surfaces and causing them to corrode. Ride on! And thanks for reading through my post and posting your answers.