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poor compression

Daves79x
Posts: 680
Joined: Sun Aug 09, 2015 8:13 pm
Location: Knox, PA. USA
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Re: poor compression

Post by Daves79x »

Hate to disagree, but neither of my two recent bore jobs (R50 and R69) had 'taper'. Both bike had great compression from the get-go and the rings seated perfectly very quickly. Others obviously have different experiences. My R50 cylinders were bored to .0025 clearance and the R69 cylinders were bored to .0030.

Dave
Dave

dellatorre6708
Posts: 62
Joined: Fri Oct 27, 2006 3:00 am

Re: poor compression

Post by dellatorre6708 »

Thanks for all the replies and suggestions. Haven't had time to ride lately.
Frank.
NYC.
Frank,
NYC

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malmac
Posts: 796
Joined: Sun Jun 29, 2014 2:10 am
Location: Toowoomba, Australia.
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Re: poor compression

Post by malmac »

An interesting thread.

I was interested in the question of bore taper. I always made the assumption that bore taper was a bi product of machining equipment that wasn't rigid enough to make for a parallel bore. So given there was going to be taper in one dimension or the other, better to have the tight end nearest the cylinder head.

Well after reading the thread, I thought is taper actually required?
So I went and did a search. Here is a link to a rather long technical article on blow-by.
Did it answer my question? Well not categorically, but I now know that I don't know much.
Well where to from here, I don't know.

https://www.enginebuildermag.com/2017/0 ... nder-blow/

Mal
mal - R69s
Toowoomba- Australia

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