Compression Tester

[Ricko]

Hi,

I'm using a Clarke compression tester from Machine Mart. Is this suitable for use on chainsaws to get an accurate reading?

Cheers

[spudulike]

You need a compression tester that has a very light spring rate Schrader valve in the bit you screw in to the plug hole. 

Usually the Gunson Hi Guage is the weapon of choice.

The only way of knowing that the Clarke unit is OK is to test it against something like the Gunson unit.

If it has the end of the valve sticking out, a very light push should push it in. If it is like a typical tyre valve, it will read low.

I modified mine with a presta valve as I was destroying Schrader valves daily on ported saws!

If your tester is reading 150-170 on a mid size saw, it is likely to be OK. 80-120 and it is likely to be not suitable.

[Ricko]

Funnily enough I bought the Clarke one to replace an old Gunson one, I didn't throw it away and realised the Schrader valve wasnt holding air to keep a reading. I replaced it and put it back in the cupboard, I'll give it a go on a decent saw to see how it performs.

[spudulike]

The Schrader valve must have a very low opening pressure. Just putting in any old tyre valve won't work. Snapon white valves work.