Compression test

[Fisherking]

This is going to sound dumb, but I'm asking anyway,lol.
When doing a compression test do you need to take the air filter off? If you don't how will it effect the result.
I have a K&N filter .
F.K.

 

[NCBILL]

This is going to sound dumb, but I'm asking anyway,lol.
When doing a compression test do you need to take the air filter off? If you don't how will it effect the result.
I have a K&N filter .
F.K.

I sure wouldn't think so. You're testing the rings in the cylinders, not any part of the intake.

 

[tourbox]

No, but make sure your throttle is all the way open for max. air.
tourbox

 

[dolt]

Won't hurt but not necessary.

 

[Fisherking]

Won't hurt but not necessary.

Thanks Guys .
Apreciate it.

F.K.

 

[Jeff Klarich]

+1 on what tourbox posted.

 

[Lobo1]

The 05 FLHTCI I just bought this past March has 46,377 miles on the clock. When I did a compression test on it shortly after getting it both cylinders had 140 PSI. I know that's great as for the +|- 10% rule between the two, but how does 140 stack up in comparison to the factory specks of a 2005 T C?

 

[dolt]

The 05 FLHTCI I just bought this past March has 46,377 miles on the clock. When I did a compression test on it shortly after getting it both cylinders had 140 PSI. I know that's great as for the +|- 10% rule between the two, but how does 140 stack up in comparison to the factory specks of a 2005 T C?

Should be about 155psi at sea level, so if you are at a higher elevations, compression will be less. Remember, both plugs out, battery fully charged, throttle held wide open and a know accurate gauge. A weak battery will show poor results.

 

[Lobo1]

Well according to the city limit signs here we are 635 ft above sea level. I did put a new battery in shortly after I did the test. Old one seemed a little tired like it had trouble getting past that first compression stroke.
I did have both plugs out and grounded. Throttle wide open. My compression tester is Matco brand and is a good one. Maybe I need to do another test now that the battery is new. Don't really know how to calculate the 635' above sea level though.

 

[dolt]

Well according to the city limit signs here we are 635 ft above sea level. I did put a new battery in shortly after I did the test. Old one seemed a little tired like it had trouble getting past that first compression stroke.
I did have both plugs out and grounded. Throttle wide open. My compression tester is Matco brand and is a good one. Maybe I need to do another test now that the battery is new. Don't really know how to calculate the 635' above sea level though.

635' above sea level will only make about a 2 psi difference in CCP; see the attached calc sheet from the BigBoyz website. Factory tolerances come into play here as actual deck height, chamber volume and piston dome volume can vary. I have seen TC88 head chamber measure close to 90cc but they typically will measure 85-86cc.

Check again with the new battery and see if there is a difference.

http://www.bigboyzheadporting.com/TwinCamComp.htm