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Yz250x low compression on rebuild


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So I threw a new wiseco piston and rings on my bike a few months ago. The damn throttle got stuck initially and went wide open. I finished the break in per wisecos instructions and but the thing had zero power. Started up fine but couldn't even lift the wheel except in first. Figured I toasted the ring and glazed the cylinder. I just now got around to putting a new ring in and scotch brite on the cylinder walls. Compression test before I pulled it apart with the bike warm and throttle open was about 160. Well I just did the first heat cycle on it and it's exactly the same. I won't be able to ride it until tomorrow after I finish the break in to see how it feels but I'm guessing it's still down on power. When I was googling what it should be it seems most people are around 200 or more with 180 being low. Im wondering if anyone can give me suggestions to what may be wrong.

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Can the powervalve cause this issue? When I did the first rebuild I found the powervalve was stuck open,it had went too far open and went off track. I'm not sure how long it was like that for, I was used to how it felt with the first 3 gears needing to be careful to keep the front wheel down which I'd expect out of a 250. From my little understanding of powervalves it seemed to function right when I had the cylinder off. I could turn it by hand the first portion which opened the main port then I needed pliers to twist it farther and open the side ports. I would have to twist it all the way closed to seal the main port since there was no spring action for that which I believe I read was normal.

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All compression testers read a little different in my experience.  The only way to really know is to take a "before and after" test with the same gauge, or use the same gauge to test both bikes (for comparison).   My YZ144 reads about ~160psi hot as well, my old KX310 read abbout 220 fresh.

The powervalve not functioning correctly can absolutely effect when and how the power comes on.  If it doesn't feel right, I'd probably inspect that.  Also make sure you don't have any air leaks.

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So I pulled the plate off and I checked that the linkage moves and opens the valves by looking thru the exhaust. However when I rev the bike up there's no movement of the linkage. Last night I pulled the reeds off and checked there was nothing wrong there and that all the bolts were tight. Ive also had an issue since the rebuild that the bike revs extremely high on first startup and I have to immediately hit the kill switch. As soon as I start it back up it idles like it should. The bike kicks over like it has compression despite still having a low reading. Also starts up in 2 or 3 kicks from completely cold. 

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^^ or you can always compare your tester against another known one.  But regardless, re your bike's comp, the effort required when you kick it over tells the tale...

Re your linkage, its going to be way more efficient for you to search this most-excellent forum, its been well-covered many times over.

Re the revving at startup, if you have the choke on when it does this, I have never been able to solve it, stupid as that sounds.  Ours did not rev completely out, but it was way too high for a cold engine to have to endure.  Workaround was palpating the killswitch with our rt hand while turning off the choke with our left...obviously SOMEONE knows why this carb only does this on YZ's, but I never was able to solve it...

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So I took the case apart to see what was going on and the governor basically fell apart. The ball bearings fell into the case lifting it out. Somehow the retaining pin for the governor came off. I'm in the process of figuring out where it went to but maybe it came out when I drained the oil at some point. I've never tore the bike apart farther than this so I'm not sure how far that pin can make it into the engine and if it needs a full tear down now. I did find a plate of metal that was lying loose on the bottom but I can't figure out what it's from. Can anyone help me identify it?

20211014_002645.jpg

20211014_002635.jpg

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