Chainsaw Repair

Thanks again for your quick response.  I bought the compression tester on ebay i.e.
http://www.ebay.co.uk/itm/Automotive-Motorbike-Petrol-Engine-Compression-Test-Gauge-Tester-Car-Accessory-A-/182569770506?rsta=en_GB(en_GB)&cnac=GB&mail=sys&e=op&unp_tpcid=email-receipt-auction-payment&ppid=PPX000608&calf=cb4ae1889e04b&calc=cb4ae1889e04b&pgrp=main:email&unptid=9ec553f2-42e8-11e7-9dad-441ea14e5960&mchn=em&t=&s=ci&page=main:email&cal=cb4ae1889e04b&cust=
The compression tester I received had no brand written on it, the details said Neilsen Tools...which I have never heard of.  The kit looks ok, but does it give the right value?  Tomorrow I am going to ask my neighbour if I can do a compression test on his stihl saw.  Its an old saw but still works very well, so I presume it will be over 110 psi.

I will remove the decomp valve tomorrow and try and order a decomp plug.

Thanks again