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Marshmellow 12-27-2010 04:02 PM

Piston Replacement Help
 
My 1st thread here, be easy on me for asking the questions I do. :-)

So I'm actually working on replacing the Pistons on a old 4 Stroke 400CC Bike engine, the previous pistons are well over the wear mark. Upon looking up for replacement pistons sadly I came to know none of the manufacturers make the pistons I'm looking for anymore, wiseco etc.

So now the best replacement pistons I have found from a different bike engine look to be identical EXCEPT the pin to deck height which is a mm shorter than the original stock pistons. I can make up for the difference of height by shaving either the bottom base of the cylinder or the head gasket surface area. Now I'm just unsure if it will cause any issues in the stroke or performance. Also if I can go ahead with the shave idea, what would you recommended to shave, the base of the cylinder or the top?

Thanks.

dgcantrellsr 12-27-2010 07:36 PM

Wouldn't it be more feasible to order oversize and have it bored, if the pistons are wore I would assume the bore is also.


Quote:

Originally Posted by Marshmellow
My 1st thread here, be easy on me for asking the questions I do. :-)

So I'm actually working on replacing the Pistons on a old 4 Stroke 400CC Bike engine, the previous pistons are well over the wear mark. Upon looking up for replacement pistons sadly I came to know none of the manufacturers make the pistons I'm looking for anymore, wiseco etc.

So now the best replacement pistons I have found from a different bike engine look to be identical EXCEPT the pin to deck height which is a mm shorter than the original stock pistons. I can make up for the difference of height by shaving either the bottom base of the cylinder or the head gasket surface area. Now I'm just unsure if it will cause any issues in the stroke or performance. Also if I can go ahead with the shave idea, what would you recommended to shave, the base of the cylinder or the top?

Thanks.


matt167 12-27-2010 08:05 PM

send the specs to Egge machine, and they can make a new 1..replacement pistons that are otherwise unavailable is most of what they do

1800guy 12-27-2010 08:22 PM

Maybe bike engines are different from a car engine - but if the piston is in good shape, why not sleeve the cylinder? A sleeve has to be cheaper than a good quality custom made piston.

Marshmellow 12-28-2010 02:19 PM

When assembled the Piston sits approximately 1.5mm below Cylinder deck on TDC inside the bore. Would you suggest to just let the cylinder be and call it a day without worrying about detonation or gas octane? Because that would be absolutely wonderful if true.

Also how much would you believe It would hinder the performance of the engine if no corrections are made to the Cylinder?

I believe the Cam chain tensioner has enough travel left in it that it will tension the chain tight without any slack, the retard timing causing the engine to peak out at higher rpm's I can deal with as well, provided I am recommended to shave the cylinder, if suggested not to then both the above would become irrelevant.

The only confusion that keeps me right now is to shave the cylinder or not.


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