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Donny p

06 478 engine noise

4 posts in this topic

ok i just rebuilt my bike after it was sitting for about a year with a broke valve and searious head damage.. anyways i got all new valves, springs, ect. and i put the cylinder works 478 kit on it. Well when i was puting the piston & rings together i skiped the steps of making sure the ring gaps were correct, completed the rebuild and when i fired it up i could tell there was not enough ring gap, It wouldnt stay running and it felt like il was tring to kick start a tractor anyway i fixed the ring gap problem and now my motor is super noisy i think it might be piston slap!! i need a second opinion please and thanks.. Didnt mean to write a novel lol.

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Maybe octane ping. Big bore with a high compression piston will not sound like a stocker. Also most aftermarket pistons have shorter, but thicker piston skirts and IMO makes more of piston slap noise than stock setup. If you are still running the stock carb jetting, you maybe running lean. Thats all I got, have a good day.

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What did you set the ring gaps to? What is the piston clearance? Who manufactured the piston?

What are the chances your noise could be excess valve clearance or perhaps an aftermarket skid plate?

While it's true that several aftermarket pistons are somewhat noisier than stock, it's because of their clearances and the shape they are cut to, and not their length (pistons must be "ground" to a precise oval/barrel contour to minimize friction and control the rocking the takes place when they reverse directions).

I imagine that the noise you hear is at idle and/or while running in neutral. It is extremely improbable that such a noise is in any way related to fuel octane, as detonation typically occurs under a load.

One last thing to consider is that working on your own bike always improves your hearing acuity, even if you are a fairly competent and confident mechanic. It's quite common actually.

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k it is the cylinder works kit it came with a wiseco piston/rings not a high compression piston i was told no need for race fuel i dont remember the ring gap i set but i used the paperwork that came with the piston/rings and the formula to convert inches to mm, i wrote it down ill look for it,

i went ahead and rode my bike today, runs good, pulls real strong, starts first kick everytime, it does sound alot like piston slap when i revv the the noise gets louder and as the motor decels the noise kinda pauses then gets quieter. Im gonna check the valves tonight ill let u guys know whats up with that part.

This might be a dumb question but if it is piston slap what are my options to correct that?

Thanks for your opinions and time

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