The Forestry Forum

Hi fellas, I am trying to sort out a sickly running Sthil 021.

I did a brief search of compression testing and couldn't find a sequence of doing this correctly by someone in the know, eg best hot, cold, throttle on, off etc. I know it's not rocket science but if someone could help out that would be great.

Thanks

Al

I haven't done a test on any of my equipment before, but I think its pretty simple like you said.  I belive you would do the test cold: attach the guage to the spark plug hole and pull the saw over until the guage stops going higher.  The highest reading should be your compression.  The throttle should not have anything to do with it, but I would leave it on normal(idle) with the ignition off. 

cold
throttle position is irrelevant
pull until it stops climbing

Thanks fellas. I have mate of a mate who is big in the motorcycle engine reco industry. I might suss him out to see if we can somehow work out the accuracy of the gauge.