2015 yz 250f big bore kit cylinder works

Jarrod458
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Jarrod458
Edited Date/Time 6/15/2015 10:04am
My friend bought a big bore kit for his 2015 yz 250f. Had a very trusted mechanic instal it. The bike had 4 hours on it and ran fine. Then with the big bore kit on it's making a clapping noise like a valve is hitting the piston maybe? I haven't heard the noise so not positive. Just trying to find someone that intalled a crank works big bore on a 2015 yz 250f. Any help is appreciated. Thanks!
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Slosh 112
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Mackay QLD AU
Slosh 112 6/12/2015 6:23pm
6/12/2015 6:23pm
If the piston was hitting a valve it wouldn't run for very long...
adub274
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Las Vegas, NV US
adub274 6/14/2015 10:16am
6/14/2015 10:16am
Cam chain slap maybe ? Tensioner stuck or guide not installed right ?

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harescrambled
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harescrambled 6/15/2015 10:04am
6/15/2015 10:04am
Does the noise you describe get quieter when the bike is hot? Was the piston to cylinder clearance checked prior to installation? If it's excessive, the noise is piston slap, which will eventually break the piston skirt, and destroy both the piston and cylinder at minimum.

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