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

 

According to my 2014 Dyna Service Manual, a minimum of 125 psi with no more than 10% variation between cylinders is considered normal.

 

Ok Thank you! Some reason I thought it would be up around the same as a Sportster I was riding for a little while. That was 220 to 225.

 

Actually, the CCP in a stock 103 should be about 195psi (sea level); if above sea level that would need to be adjusted down. The number will vary a bit from motor to motor depending on the condition of the top end, actual chamber volume and deck height but it shouldn't vary much.

 

Thank You . Can you tell me where you heard 195 psi was the correct pressure? IdahoHacker's post is showing 125 psi as coming from the service manual. Is your number another figure from the manual? Maybe the highest reading the bike should show? The more I search this topic the more confused I get,LOL.

 

The service manual says a minimum of 125, with no more than 10% variation between the two, is normal.

The service manual is all about whether or not the bike needs service. So, if both cylinders are 130, no engine work would be considered necessary.

That's not the same as what compression you would see in a brand new engine.

 

I used my compression calculator and I have pulled compression tests on a couple of 103 motors that have been upgraded with the Stage IV kit; those will see 210-215psi CCP. Go online and look for a compression calculator, plug in the data and you can see for yourself. Remember, the numbers I posted are general and not specific to your motor as there may be some variances in tolerances but your actual numbers shouldn't vary much from those general numbers. Also remember to adjust for sea level.

 

check on bigboyz head porter site there a calculator there

 

Took a look at the Big Boyz calculator. But the amount of info they want imputed is a little over my head.

 

All you need to know to get in the ball park is displacement (bore/stroke), head gasket thickness, chamber volume and dome volume. Use the defaults for chamber and dome volume for a stock motor; you can ignore deck height. Use the OEM head gasket thickness and 30* for the intake valve close as the OEM cam for a '12 model is not in the cam selection list. Adjust for sea level and you have it.