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Piston compression psi help

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rush

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Hey I need some help finding the correct PSI reading when doing a compression test on a 2012 wide glide with a stock unmodified 103 engine. Anybody know what it is? All the searching I've done here and other places has only given me PSI readings on modified engines. Not a stock 103.

Thanks in advance for any help
 
Your engine is 9.6-1 ratio doing the math it brings it out to 141 psi.

The math: 1-1 = 14.7 psi... now the magic 2-1 = 29.4 psi... that is 2*14.7 = 29.4 psi.

:)

General rule of thumb 135 psi or better is good for gas engines.
 
rush said:
Hey I need some help finding the correct PSI reading when doing a compression test on a 2012 wide glide with a stock unmodified 103 engine. Anybody know what it is? All the searching I've done here and other places has only given me PSI readings on modified engines. Not a stock 103.

Thanks in advance for any help
Click to expand...

Welcome to The Forum
With a good gauge no leak down and throttle full open you should see 180 lbs both cyls +or - 5 to 10 lbs If you have ACR be sure they are working properly before you do a test
 
Thanks for the reply's, and I do appreciate the help, but the first reply is 135 psi the other 180 psi. So I'm still stuck on what I should be seeing for a reading.
 
My Twin Cam service manual does not have compression values, but both my Evo and Shovelhead manuals say compression should be over 90 psi. @ operating temp., with less than 10% variance between front & rear.
The 180 psi Jack mentioned is what I normally think of as good. This is for stock or moderate cams. Cams with a lot of overlap, can significantly change the numbers.
 
Ok I last heard 125 psi from someone who said they had a service manual. But that sounds low for a 103 engine. The psi for a sportster I rode for a little while was 220 to 225.
 
Sportster, Fatboy, 1200 cc, or 400 cubic inch, pretty much the same. It's psi, not total pressure.
 
rush said:
Hey I need some help finding the correct PSI reading when doing a compression test on a 2012 wide glide with a stock unmodified 103 engine. Anybody know what it is? All the searching I've done here and other places has only given me PSI readings on modified engines. Not a stock 103.

Thanks in advance for any help
Click to expand...

Stock 103" using the stock 30* intake cam and .045 head gasket...

.....static compression= 9.87:1
corrected compression= 9.43:1

Sea-level should Pump 196.7 PSI

signed....BUBBIE
 
rush said:
Ok I last heard 125 psi from someone who said they had a service manual. But that sounds low for a 103 engine. The psi for a sportster I rode for a little while was 220 to 225.
Click to expand...

125 would be the lowest reading before HD would be concerned with engine problems, the 96 motor calls out for 100 being the low number
 
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