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How common is a little bit of oil/gas mix leaking from power valve cover?

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So after 5 hours of riding pretty hard but with a lot of 1st and second gear technical stuff, there was maybe about 2 table spoons or less worth of mix (I am guessing that is what this is) leaked out of the cover on the right side of the motor from that flimsy rubber gasket which is the bottom of the power valve linkage cover I believe. How common is this? I hear it is pretty common and with that small amount coming out not much to worry about really. I did however just order the oil seal for the powervalve shaft but it looks like I will have to pull the motor to install it. Like I said it barely leaks so if I do have to remove the motor to replace the seal is it safe to just ride until it needs a new top end then I will just clean and rebuild whatever needs replacing in the power valve? I just replaced the gasket to the power valve cover and the flexible rubber gasket at the bottom that is shaped like an "L"-the guy I bought the bike from is kinda not smart to say it nicely and he said it was leaking water as in coolant and I told him that its not coolant its mix. My local bike shop mechanic I know pretty well said it is pretty common and not really anything to worry about with minor seepage. What do you all think? The new top end has about 10hrs on it so is it safe to ride until it needs a new top end and then replace the power valve stuff to stop the leak or does it need to be taken care of ASAP?

Edited by YZF1825

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It's really common. Caused by a worn alum hole where the PV shaft bears on the right side (under your linkage cover). The little seal cannot cope with the enlarged hole, so premix oil leak through. The linkage cover never seals perfectly and shouldn't have to if that upper seal was ok. The fix is to get a machinist to press a brass bushing in that hole. Which is bit of a hassle to get done, but the good thing is it's fixed for the life of the cylinder and the PV shaft wont wear either.

A semi-fix is to try find/make a fiber washer which can go in there instead of the seal. Get one with the right OD, ID and thickness then push it into the space, and it'll seal surprisingly well and also take some of the pivot load if you get a 2mm thick washer. Just replace every 50 or 100 hrs or so.

Either way you need to remove the cylinder. But not the whole motor.

BTW: You can make your motor produce much less black oily mess by fixing the rich jetting. So the premix oil will burn properly.  Then you can lug around a lot and have no black spooge leaking out the exhaust from anywhere. I'm not super fast and don't rev the motor much and use thick 800T or 927 castor premix oil at 40:1 and no spooge. And my motor is not jetted lean. Not rich either. This is possible with the zook NExx needle. Don't think you can run the Yam needle and have good power and no spooge.

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it isnt spooging anymore since I switched to Yamalube 2R. How do I do this bushing fix? And if I don't do the fix and just replace the entire cylinder when it comes time to do the top end can I go that route? There is easily 50+ hrs left on this top end.

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Make sure the vent tube on the left isn't blocked. Most excess pressure/oil will come out of it if its unobstructed 

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