Evo Compression test
Evo Compression test
I have a 94 FLSTN. I'm rebuilding the motor due to a base gasket that is common on the EVO. I've decided to put some KB 10.5:1, .030 over stock, pistons in while I'm that far into the motor. It has flat top pistons in there, and I belife they are stock.
I tested the compression and it was 150 psi on the front and 140 on the rear cylinders. Can anyone tell me what is the normal PSI should be on an EVO motor? Most of my other bikes have been around 90 PSI
I tested the compression and it was 150 psi on the front and 140 on the rear cylinders. Can anyone tell me what is the normal PSI should be on an EVO motor? Most of my other bikes have been around 90 PSI
Seasoned HDF Member
Joined: Jun 2010
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From: Upstate New York
My '94 FLSTN (stock motor/stock "N" cam) reads 150 PSI front/150 PSI rear hot. I feel the service manual recommendations are way too generous.
Ten percent allowable variation sounds about right though.
Ten percent allowable variation sounds about right though.
Road Master
Joined: Oct 2011
Posts: 957
Likes: 2
From: Carlsbad Springs Ontario
Above values are as described " pristine mother Harley values " .
If your press. values are within 10 - 20 lbs. you should be ok.
Its not the high lps. you should be consirned with but the dif. between each,.
If your press. values are within 10 - 20 lbs. you should be ok.
Its not the high lps. you should be consirned with but the dif. between each,.
Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
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From: Coromandel Peninsula New Zealand
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Ok guys. thanks for the input. The motor is back together and is at 175 both cylinders. I've also rebuilt the carb so I just have a few minor things to fix and she's back on the road!
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Feb 1, 2016 02:08 PM