NEED HELP! 2007 kx 250f

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5/8/2018 10:34 PM

just rebuilt the top end on my 07 kx 250f and I had the head shaved down a bit at a machine shop I got it running has a loud clattering noise rode it for maybe an hour then I took it home took it back apart and the exhaust valves had cut down into the piston slightly didn't really damage it bad would this be from timing or because I had the head shaved down? it also drips oil out of the breather tube. any help is greatly appreciated.


5/9/2018 5:23 AM

If the valves are hitting the piston, then yes. Make sure the valves aren’t damaged or bent. You’re lucky they didn’t bend or break and drop into the piston.

The valves need to be shimmed more.

Why did you have the head shaved? Was it warped?


If you're not mixing gas, you're not haulin ass.

5/10/2018 8:00 AM
Edited Date/Time: 5/10/2018 8:23 AM

Having the head shaved will throw off timing and you'll never be able to set it correctly unless you have cams with variable gears or you get the cam gear moved. Either way, you have to degree the cams. Shaving the head also will shorten the distance between valve and piston causing them to contact too. You could have set the timing one tooth off and it still run. Valves hitting the piston I wouldn't trust that piston, crank, main bearings, or valves. Especially after riding it for an hour. Dripping oil from breather tube is from excess crankcase pressure, could be caused by blow-by from the rings. An experienced engine builder can put it back together but shaving the head down made things much more complicated. How much was taken off the head?


5/11/2018 11:27 PM

it was leaking oil from a new head gasket so I took it to a machine shop and he said it looked a little warped so he machined it down and idk how much he took off but the valves left a slight indentation in the piston but on the exhaust side only so I'm not sure if I could maybe put a thick base gasket and bring up the cylinder up some to bring the piston down more or what I should do.


5/11/2018 11:32 PM
Edited Date/Time: 5/11/2018 11:33 PM

I also have an automatic cam chain tensioner and now I have to preset it and put it in half way out because my cam chain don't tighten unless i leave it half way out were it was shaved.


5/11/2018 11:38 PM
Edited Date/Time: 5/11/2018 11:40 PM

it has to be out of time from having it shaved how can I time it since my head is shaved down.