# Compression check on a Honda



## orangputeh (Nov 24, 2016)

Checking the compression on my machine it only registered 80 pounds. Thought it would be around 120 or so.

then i watched a u-tube that shows you have to disconnect a rocker arm because there is a compression release on the valve?

this is confusing because if there is why would mine register 80? this guy did his and it showed 80 pounds and then he released rocker arm and it registered 120.

so how do you check compression on your Honda? the shop manual does not show what the compression should be.

what is a healthy compression?


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## YSHSfan (Jun 25, 2014)

I don't have my HSXXX Manual handy but my HS55/HS80 manual has instructions for compression check and all it states is:

- remove spark plug
- install compression check tool on spark plug hole
- crank engine several times with pull cord 

Spec on this engines is 
85-121 psi @ 600rpm (when decompressor is engaged).

My feeling is you need to pull the engine cord faster or more times (unless you have a tired engine).

I've checked compression in the past on two of my HS621 (gx160 engines), the compression on them was at about mid area of the spec range. (I do not believe that you need to do anything with the decompressing mechanism to be able to do a compression check as the spec supplied should take the valve into consideration).


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## drmerdp (Feb 9, 2014)

The decompression release bumps the exhaust valve open slightly to make the engine easier to pull start. It is integrated into the cam on most engines, I believe Honda is the same. It's active until centrifugly disengaged as engine speed gets to operating range. 

Id imagine that the service manual spec accounts for decompression psi. Loosening the exhaust rocker will give you the accurate number.


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## orangputeh (Nov 24, 2016)

drmerdp said:


> The decompression release bumps the exhaust valve open slightly to make the engine easier to pull start. It is integrated into the cam on most engines, I believe Honda is the same. It's active until centrifugly disengaged as engine speed gets to operating range.
> 
> Id imagine that the service manual spec accounts for decompression psi. Loosening the exhaust rocker will give you the accurate number.


thanks. will try.


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