overhauling an older xt350

I have recently returned after a ten year hiatus to the sport ,so naturally iwent out and bought the nearest fair size p.o.s It ended up to be a 95 xt350 with lots of experience so after taking it for a ride at 50mph i noticed it all but went into a speed wobble when the steering was even slightly corrected After adjusting the the front fork and wheel bearings it now seems better but still not 100% Also when reving the engine close to the redline ,and then closing the throttle it smokes badly [blue] Where do i start on this little cream puff ? Do you think its rings causing the blue smoke or valve seals ?Also after putting this thing through its paces i see oil seeping past a lot of the engine seals so i feel its likely blowby and therefore needs rings anyone have any thoughts on this Where is the best place to shop for aftermarket parts? thanks in advance

Sounds like your engine is pretty worn. :) Blue smoke could be rings, cylinder walls, valve guides, or a combination of problems. You really won't be absolutely sure till you crack it open and check. I think White Brothers might make a piston/ring kit for it, but I don't have my catalog anymore to give you the part #'s. White Brothers homepage

The first place I would start is to get rid of that P.O.S. A friend of mine had one. If you are looking to do anything more than street ridding with the ocasional 2-track thrown in then that aint the bike 4 you. The front forks are horible. We tried ridding his offroad and they bottom baddly on the tinnyist little thing. We ended puttin a few lbs of air in the forks. This helped some but that aint the answer. My buddy, who wasn't really into offroading or mx at the time, was not happy with his bike @ all.

I dont mean to mock on your bike. Its great that your ridding again. I just wanted to share my opinion of that bike.

Thanks guys your posts they have been most enlightning even you yz man, negative critisism is ok by me [say what you think thats what these boards are for]I intend to use this bike 95% on the the street, but i live in the the country ,so i think this bike will be more suited to my needs than a street bike I intend to antaganise my old riding buddies into maybe getting back into it. I would still like some more input from some of you as to how to make it go and what could cause the wobble at highway speed THANKS IN ADVANCE SPEEEEEEEEED

I ride a 1986 XT350 and have done a few things to improve it's capabilities. I changed the fork oil with a heavier weight which stiffened it up a little so that bottoming out wasn't happening all the time. I went with the Supertrapp IDS2 race muffler, dual stage UNI filter and am about to re-build the carb with some jetting changes. Are the fork tubes installed in the exact same position for left and right? The height of each tube in relation to the the other needs to be exact.

Sounds like a cool project. :ride:

The smoke is easy.

If it smokes MORE as the RPMs increase, your cylinder is worn. You will get cone-shaped pattern from normal wear on the cylinder. The higher the RPMs, the rings cant fill in the gap fast enough and oil blows by.

If it smokes when coasting the engine at any RPM (no throttle) that usually only means rings. Under load the rings are "press-against" the cylinder wall by the expanding gasses, thus they seal up to the cylinder wall and it wont let oil by into the cylinder.

If it smokes the worst right after starting it up it is valve-guides usally. Oil drips down off the valve-guides slowly accumulating....even when engine is off, thus the reason for more smoke when you start it. Under load the rings are "press-against" the cylinder by the expanding gasses, thus they seal up to the cylinder wall and it wont smoke under load

Why not try putting a set of rings in her? It would be better to bore it though and slide in a new matching piston. Not sure what that would set you back.

Maybe opening up the side cases (not splitting the case) for a peek? You will gleen much on the overall condition of the engine, clutch wear, etc, not to mention when you put her back together (new gaskets) you may fix some (or all?) of you leaks!. :banana:

This would take you and evening to do, not require any fancy tools other than a ring compressor and, if your like me, you would love every second of it!

Good luck, and post some pics!


The first place I would start is to get rid of that P.O.S.

I disagree. I had a 1987 XT350, which is basically the same bike. It was a great little trail bike. Furthermore, it had 6 gears and did well on the road. I went everywhere on that little bike. It was the last bike I used to ride 30 miles on-road to go trail riding then rode home. It was very reliable.

Here are pictures of my 1987 when I finally sold it in 2004. It ran great.




Yeah my '95 suits me fine. My clutch side gasket has been leaking oil as well. I hear this is a common problem. Hope your troubles aren't too major...

Yeah, don't believe the nay-sayers. I had a 1992 that I put 4000 miles on before it was stolen. Everything from fire-road exploring and city commuting to a 250-mile day trip on the freeway and then into the bush and home again. Nice simple design, and easy to get at most parts. I've got a Yamaha service manual that doesn't have a bike to go with it anymore.. I'll sell it cheap if you want.

My "POS" only lasted 17 years and something like 30k miles of serious abuse - mostly offroad. So don't sweat the negativity. For one thing because that post is right about the forks. The forks really are junk.

The cylinder head is the most fragile element in the engine. So check the valve clearance regularly. They don't need adjustment often, but when they do you must take care of it. That also means watching the cable adjustment on the auto decompression.

You might want to replace the front wheel bearings rather than "adjust". They had issues with some of them. Mine spit all the bearings out of one side of the front wheel at high speed one night when it was only a few months old.

Make sure the top of the fork tubes are flush with the top of the triple clamp. That was the factory setting. Mine came setup from the dealer brand new with the fork tubes up about an inch and it wanted to tuck and would even headshake.

I second moving up from 10wt fork oil to 15 or 20. I used 15wt and made preload spacers that helped with bottoming. I never did run air pressure. But there is no cure for them being too small and having pathetic damping.

I also second opening it up having the cylinder honed or bored and slapping in at least new rings and maybe a forged piston. Also, since it is shim and bucket valve adjustment that requires a special tool or cam removal to adjust the valves anyway, you might want to let a shop replace the seals and readjust the valves while it is apart.

If you do the disassembly and assembly work yourself you can freshen the top end for very little money. To me, anything over $400 or $500 in repair cost says start shopping for a new beater. That was why I parted mine out the last time the top end grenaded. With the head destroyed it was going to be pricey.

Hey guys, I'm the guy who had the XT overheat on me going down the highway. I'm still not sure what made it overheat, but I know that engine ran really hot. So hot I was scared to let it idle at long stoplights. Anyway Mine always did have a high speed wobble. I blamed it on a bent front rim. It could also do that if the bead was not set right on your tire. Mine also had a lot of leaks around the top end. I am currently rebuilding my topend , and The parts are mainly pretty cheap. Just keep in mind the 350 is a 250cc cylinder that is bored out to a 350. This means the cooling fins on it were designed for a 250cc. Think about that before you go and bore it up to a 400 or something. Don't overwork it and maybe look for an oil cooler. I never would have guessed that mine would let go on me like it did.

Where did you get this info??? :applause:

"Just keep in mind the 350 is a 250cc cylinder that is bored out to a 350. This means the cooling fins on it were designed for a 250cc." :bonk:

Corky :prof::D:prof:

A Yamaha technician warned me of this issue. He said these bikes were never really designed properly due to lack of cooling ability for the output of a bigger bore. And that is why they stopped making 350's. Same for Honda and Suzuki

A Yamaha technician warned me of this issue. He said these bikes were never really designed properly due to lack of cooling ability for the output of a bigger bore. And that is why they stopped making 350's. Same for Honda and Suzuki


Honda XR 350 were only made for 3 years 83,84,85.

They did have some heating problems on the 83 &84 when going slow on tight trails. This was mainly due to jetting to lean.

85 Honda went to a dry sump motor and solved a lot of heat problems but were generally still jetted to lean.

Fatten them up and heat problems went away.

Also many riders didn't know how to start 4strokes and when stopped they didn't stop the engines= overheating.


DR350 was bullet proof. It came jetted to lean for all conditions. Damm ECO- RATS. Jet them correct no overheating.


Yamaha 350 was made from 1985 thru 2000 with no changes except for the color of the plastic.

The Yamaha enginers know more than most motorcycle shop wrenches.

I think your Yamaha tech is wrong.

The barrels on the 250 and 350 are different!!

Again these bike are most all jetted to lean=overheat.

The EPA freaks cause the manufactures to jet them lean to get approval to sell in US.

I got a little windy, I have ridden XR 350 & XR 350 motorcycles in Baja at near race speeds for hours at a time in 100 + degree heat an had no problems.


Corky :D:applause::prof:

Well if thats true then explain to me why the 650's, 400's, and 250's don't overheat(I'm sure some do but not like the 350). my DR650 doesn't get anywhere near close as hot as that XT did. That bike used to just about burn my legs, with the DR I can't even feel any heat coming off it. I'm sure the lean jetting didn't help, but the xt has a lot bigger problems then lean jetting. All in all it is a bike to be avoided, trust me I know. I'm not even sure why I'm bothering to rebuild it. By the way Corky we have the same birthday :applause: Only I'm a good bit younger than you.

The XT350 overheats because:

a: it came jetted too lean

b: it is a wet sump engine

Too me, the only serious engine design issue is the overly complicated head. Shim and bucket valve adjustment in a low power DS bike is just plain stupid. A lot of people end up never adjusting the valves because of the complexity and/or cost. Which is why you almost never see XT350 heads on eBay. However, the up side is that the engine can be made to scream without compromising reliability.

As to the wet sump design, like I have said before I changed the oil after EVERY ride. And I only ran full synthetic. Even though the clutch cover got about as hot as the surface of the Sun, mine still had the original clutch and the cases had never been split after 17 years and 30,000+ miles. I did plenty of riding with the throttle pinned and grinding though ridiculous amounts of mud in SC heat with no reliability issues from heat.

That said, I wouldn't put much money into rebuilding one that I bought cheap. I kept mine going because I had bought it new and modified it to suit my taste so it had sentimental value. But starting from scratch I would buy a better bike to start rebuilding. IMO, both DR's and XL's have better suspension and an easier engine to work on.

weisco still lists the pistons for this bike. I'm using mine mainly on road and set the valves every 6000km as recommended by the service tec. mine is a 2000 xt350 so i only have 10,00km on it currently. the xt225 i had previously was starting to exhibit these same symptoms when i sold it with 18,000 km on the little bugger. she needs the jug hogged out one size with new piston and rings. bro is doing this to his xt250 currently. just order the complete gasket kit when you get it (bout $50.00 Canadian) and it will have all the gaskets to fix all those other oil leaks. check all wearing parts while you got it stripped (timing chain, clutch etc) and you should have it back together for under $500.00 without labor if shes not too bad. if she is part her out on ebay as the head should make a killing cause its that rare.

as to the front rim shake carefully replace the bearings as i have just broken 2 hubs doing this on my bike. then check it with a dial indicator for out of round and side to side movement. i think Yamaha spec is like 10 thou or something ridiculous. get it as close to "0" as you can and it should make a huge improvement.

I have been beating on my 86 XT350 for 5 years and have put over 4000 hard off road miles on it. Besides damaging some of the street worthy stuff it has been great. I over maintain the machine so that I can always get home and continue to dig DEEP sand and mud with no huge worries. I actually rooster tailed so much mud last season that my license plate blew off somewhere on the trail. Key is to maintain before a problem occurs and you will continue to enjoy.

Where did you get this info??? :applause:

"Just keep in mind the 350 is a 250cc cylinder that is bored out to a 350. This means the cooling fins on it were designed for a 250cc." :bonk:

Corky :prof::D:prof:

That isn't right. They are different cylinders. The 250 has an extra oil passage on the cam chain side. You can see this for yourself on one of the many sites out there that show engine blowaparts. That said, much of the 1984 XT250 and the 1985-2000 XT350 are identical (including the bottom end). In fact, I could be mistaken, but I think the only significant difference between an '84 XT250 and a '00 XT350, besides the cylinder, is the front end (forks and front disc).

On my '89, I farmed out the head rebuild and the cylinder boring, got a Wiseco piston and rings and put the top end back together myself for around 300 bucks total IIRC (maybe less than that). All told I put another couple of hundred maybe in it over the 2 or so years I had it. Sold it last month for a good price. It was a great dollar to fun ratio.

Pay attn to carb boot leaks and anything else that gives you a lean condition, because that will make it run very hot. If you keep it cool, it will go forever. It may not be a motoxer, but it's a pack mule in the woods.

As far as the wandering on the highway, body placement on the seat and not keeping a stiff grip on the bars alleviated that. A tight hold, and sitting way back in the saddle caused it to oscillate and feel vague.

In many ways, it was better than my newer DR 650. Well, except for all the extra oomph. :applause:

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