1991 RM 250 Question

[2strokes4life]

Hello all! I just put a new top end on my 1991 RM 250. I had to have my cylinder replated as well. I rebuilt with a Wiseco piston and cometic gaskets/o-rings. It is all back together now and almost broke in. I noticed there is smoke coming out of the cylinder vent hose. I'm assuming this is normal being a straight tube to atmosphere. I bought this bike with problems, so I'm not sure if they all do this. It starts on the first kick, has great compression, and runs really strong. I just want to make sure all is good. Thanks in advance!

 

[bwood]

This is normal, it is a vent on the chamber where the powervalve lives.

 

[2strokes4life]

Alright here is my next question. I was really worried because it is not idling very well now. It did at first, but now it wants to die if I don't stay on the throttle. I performed a leak down test. It wouldn't even pressurize because the air was coming out of the vent hose. I pulled the clutch cover side off and looked at the right crank seal. It looked good to me, but I pulled it anyway. I just ordered the seals for the right and left side. The crank is tight. There is no play in the bearings at all. Does this sound right to you all. I am correct that air shouldn't leak out the vent tube during a leak down test, right? I haven't pulled the left crank seal yet because i don't have the flywheel puller yet. I have heard people say that the center seal can go bad also. Would that cause a poor idle? Like I said earlier it starts on the first kick. During the initial break-in it was idling good, but the idle started to become really high when I first started it and now it won't idle for anything. Thanks in advance for the help.

 

[dans9717]

Top end

Make sure you re-torque the head nuts. I just did the top end on my 89 RM250 and it either wouldn't idle or it would jump around alot. After I tighened down the nuts again, I had no issues. Also, a bad crankcase gasket could cause a bad idle. Try the head nuts first and see if that helps. Good luck! :cool: