Kx250f valves hit piston

kelal9698
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kelal9698
Edited Date/Time 11/12/2022 6:06am
Rebuilding 2011 kx250 everything new je piston head crank timing chain, valves are hitting piston. Piston is at tdc timing mark is on marks any ideas cams marks seem to be a hair off. Either way I turn motor over valves hit without turning it much.





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kelal9698
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kelal9698 11/5/2022 11:52am
11/5/2022 11:52am
captmoto
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captmoto 11/8/2022 8:21pm
11/8/2022 8:21pm
Aren't the timing marks supposed to be straight up? One cam looks to be off by one tooth.
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EAmato88
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EAmato88 11/10/2022 7:18pm
11/10/2022 7:18pm
Did you change the valve springs?
Wrench
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Wrench 11/12/2022 6:06am
11/12/2022 6:06am
I had a KX250F same year come into the shop with the same problem. I would line up TDC and the cam dots and it would contact valves to the piston. I figured out that the cam had spun in the sprocket. The cam lobes were the giveaway. They are supposed to be up and out basically at a 45 degree angle. I believe it was the exhaust cam. I would time it all up and check angle of the lobes. New Hotcam did the trick. Best of luck.
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btroxler
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btroxler 12/7/2022 11:30am
12/7/2022 11:30am

Show us the cam lobe position at TDC. That will help 

Tumic
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Tumic 12/12/2022 5:37am
12/12/2022 5:37am
Wrench wrote:
I had a KX250F same year come into the shop with the same problem. I would line up TDC and the cam dots and it would...
I had a KX250F same year come into the shop with the same problem. I would line up TDC and the cam dots and it would contact valves to the piston. I figured out that the cam had spun in the sprocket. The cam lobes were the giveaway. They are supposed to be up and out basically at a 45 degree angle. I believe it was the exhaust cam. I would time it all up and check angle of the lobes. New Hotcam did the trick. Best of luck.

Yes, gears spinning was a thing on those engines.

I ran a JE piston in one of my bikes back then and ended up with a extra washer for the spark plug. That JE piston hit the plug and took away all the electrode gap.

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