YZ250 Power Valve issue

[BigYZ]

I ride an 84 YZ250 (Don't laugh) and up until now it has run great. Now all of the sudden the power valve seems to be having issues. There is a small retainer that holds the power valve from moving around right under the power valve cover. For some reason the thing keeps snapping that retainer and the bolt that connects the two pieces of the power valve together keeps rattling out and the power valve stops working correctly. I finally made a retainer that is stronger than the stock one and used that for a while and haven't had that same problem. Now all of the sudden it just seems as though I have no power band, like the rpm just stops climbing when I reach certain point. I am going to take the valve out and clean it up and make sure it's aligned properly and I am hoping that will do the trick. Do any of you know why it would be doing any of this? What would cause it to constantly break the retainer? Do I just need to get a new power valve? Any help on this matter would be great.

Thanks

 

[Jeff Howe]

My 85 YZ 250 did the same thing way back then. I don't remember how I fixed it, but I do remember getting a new powervalve and don't think I had the problem again. I bought all the parts related to it including that new travel limiter on the left side of the jug(shifter side). I also recall it being kind of spendy.

Ask Eric Gorr, he might know the answer to that one.

 

[jacksoj]

My neighbor's '85 YZ250 had the same problem. We fixed it with a side plate from a chain link. It was just the right size. I can't remember if we had to put a washer under is to shim it out and let the powervalve rotate freely or not. For your lack of power issue, make sure the powervalve is rotating with the keeper you've made. If I remember correctly, we could keep the right side powervalve cover off and watch it move as the engine RPMs changed.

Are you using threadlock on the bolt that keeps the two halves together and making sure to torque it properly?

 

[BigYZ]

Originally posted by jacksoj
My neighbor's '85 YZ250 had the same problem. We fixed it with a side plate from a chain link. It was just the right size. I can't remember if we had to put a washer under is to shim it out and let the powervalve rotate freely or not. For your lack of power issue, make sure the powervalve is rotating with the keeper you've made. If I remember correctly, we could keep the right side powervalve cover off and watch it move as the engine RPMs changed.

Are you using threadlock on the bolt that keeps the two halves together and making sure to torque it properly?

That's really funny that you say you used a side plate from a chain, cause that's EXACTLY what I used. I am also almost convinced that I did indeed pinch the valve so that it doesn't move freely. I will have it out tonight, I will clean it up and see if I can find a washer so that it will move freely.


Thanks to both of you who replied, this really helps.