Comp test after rebuild

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Simba
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Comp test after rebuild

Post by Simba » Thu Oct 01, 2020 9:57 pm

Hi all,
I’ve just fully rebuilt my KR1S engine and have found the compression test results to be just above 90 psi on both cylinders (disappointing).
I initially rebuilt the top end with standard base gaskets, and the squish was around 0.6mm. Assuming the head had been skimmed ( and concerned the compression would be to high) I fitted a thicker base gasket to give me a squish of 0.8mm. (I was expecting 130 ish psi).

Just to add, the head looked bog standard. And I compression tested it by kicking it over a few times quickly. It has new mitaka pistons and re-plated cylinders and crank rebuild.
I did phone BDK who supplied all parts and rebuilt crank, the guy I spoke to said that it’s fine and what he would expect.
I’m interested to know what the opinion of the experts on this forum think, as the manual says compression minimum should be over 106 psi.
If it’s going to run nicely and be reliable like this no problem as It’s a street bike. Cheers

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JanBros
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Re: Comp test after rebuild

Post by JanBros » Fri Oct 02, 2020 10:13 am

I've never done a compression test on a 2-stroke.
I only measure the effective squish with the engine complete and cut the head to the compression I want.

besides, your engine is new and the rings need running in. I'de measure compression again after 1000 km's or so.
My ultimate goal is to die young as late as possible !

Simba
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Re: Comp test after rebuild

Post by Simba » Fri Oct 02, 2020 11:07 pm

Thanks for the advice. I’ll do that

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