QuestionI just bought a 1986 yz125s with no manual,i have rebuilt the cylinder and put in a new piston but i dont think the exhaust power valve is working.It starts up and idles good but when i crack the throttle it seems pretty boggy.I also took off the cover on the side of the cylinder where the power exhaust arm goes into the cylinder and started it up to see if that arm was moving at all! and it is not,maybee just a little bit but i think that is just from vibration,All the power valve parts to it are there and in good shape.Also i have no back rim for this bike (it is craked,spokes are looooose! lac of maintenance so i can't run it through the gears)? How much should that arm be moving and is there a certain way that the power valve should be timed with the piston? Also anyone with info on a back rim for this with spokes and or hub would be greatly appreciated! 1.85 inch rim
PS. The dealer where i got the engine bore at said the power exhaust valve was in good shape.
PPS. I think it was in such great shape because i don't think it was working at all for a long time in it's previous life! Old school dirt rider wanting to ride again!
AnswerWell, I could go into a long discussion about the power valve, but you have the opportunity to do the following first: bring it back to the dealer!
If you paid to have a dealer do an engine bore and he checked the power valve and told you it was good - then bring it back and show him what it is doing.
Otherwise, you will need to undertake adjusting and inspecting this valve, which is very precise and needs to be in perfect tune with the piston action. If you start doing this, then you can't bring it back to the dealer to complain - kinds of voids his work.
There is a big possibility that your problem lies in the carb/fuel area.
Also - get a service manual from clymers if you attempt working on it yourself.
I believe I answered what you're looking for, if not let me know. Please leave me feedback ratings.
thanks
Anthony
'Ride Today - Live Again'
