Ok, well I got my 250r back today from the shop. I really wanted to race sunday, but its not fixed. They put new crank seals in it, and said that it needed them, charged me 70 bucks, and then told me they didnt fix the problem. I picked it up, and got it home, still smoking like before. Its obviously more than a simple jetting problem, I havent seen anything smoke this much in my life. I checked the oil which I just changed a week ago, none in there. Its burning the engine oil. My question is, how the heck does this happen? And how do I fix it? My mechanic thought maybe a middle case gasket? Could this be? How hard is that to put in? I am not wanting to pay another 60 bucks for labor or more.
Thanks everyone

 

the piston rings might be bad.

 

For $60 they had to only replace the crank seal on the fly wheel side. The crank seal on the clutch side is the one that lets the tran oil into the piston. If you are using tran oil, the seal on the clutch side needs to be replaced. To replace it you must split the cases. Ffirst I would check and make sure that you are using tran oil, before you go and split the cases. Fill it with the correct amount of oil and run it and then check the oil to see it it has used any. I would be thinking about finding another shop to have your work done if they tried to fix it for only $60. ASk them what seal they replaced? The one on the flywheel side does not cause trhe quad to smoke, just lose power. If this is you problem.

 

They told me they replaced both sides. However, when I called the guy I bought it from, he told me that he had just replaced them before I got the motor a week ago! So I KNOW THEY WERENT BAD IN THE FIRST PLACE!!!
I am not givin that shop my business any more, thats for sure.
I was thinking that the rings could be bad, or maybe that the floats on the carb are sticking! That just may be it, I left the gas on all evening and when I went out there fuel had leaked out. So I am thinkin thats my problem! Thank god.

If you have any other ideas, feel free to let me know as this may not be it.
Thanks everyone

 

I agree with TPRENDER's post - you need to determine IF you are burning transmission oil or NOT. That will determine where you need to investigate next. Bad rings will NOT make a 2 stroke motor smoke!! There should be no oil in the crankshaft/connecting rod area, except what is mixed with your gas!

 

I dont buy that bad rings dont make it smoke. I broke both rings on my right cylinder and the right was smoking pretty bad. Not as bad as his sounds like its smoking. But it did run like crap. I cant belive the shop said they changed the seals for 60 bucks. They must have a great secret (or screwed him real good).

 

I know WV250R said that bad rings will not make a 2-stroke motor smoke, because that doesn't change the amount of oil in your mixture. I can agree, but it may however determine whether your are running leaner (less smoke) or richer (more smoke).

First determine what the smoke is. You can definatley smell the difference between 2-stroke burning and tranny oil burning.

I just rebuilt my 250R top end 3-months ago and it ran fine until one day it started smoking, well I put in a #148 (getting a little nervous too). After running it, it was still bad, so I pulled the head and cylinder out (30 minutes) and in my cylinder were 2 large gashes in the cylinder were the piston pin circlip had came out and the pin was machining down my cylinder. With a Fatty pipe, the thing is so loud I couldn't hear this happening. Check this. It will take you 30 minutes if you are a mechanic of any kind, which I see your postings on here and you seam to have some mechanical skills. If not, grab a manual and a freind and follow it step by step and you'll be o.k.

Once you fix the problem, post again.. I would like to know what it was.
Nick

 

What do you guys think about the idea that it might be the floats sticking instead of an internal engine problem? The way its running ok on the top end of 5th and 6th sounds like maybe its just getting too much fuel from the carb possibly. Then with it leaking fuel from the carb while sitting with the gas on, I think its possible. It did this before, but it didnt smoke so badly then.

 

I think that is possible. You will be able to tell that as soon as you pull the bowl off.

 

CTBANSHEE, In your case you are right. With a two cylinder motor, one set of rings could be bad & the other set OK. The cylinder with the bad rings would smoke more, because the gas & oil mix wouldn't be burning completely, due to the loss in compression. However, with a single cylinder, like a 250R, if the rings get real bad it won't run or will bearly run. Also, Rhino99 said, "I haven't seen anything smoke this bad in my life." Which leads me to believe we are looking at a lot of smoke!