Hi Ken,
Below 70 PSI: This is generally considered too low, and indicates a significant issue like worn piston rings or a scored cylinder. It's unlikely the saw will start or run well at this compression.
90-130 PSI: This is a good range for a smaller 2-stroke chainsaw, and it should start and run reliably if other factors (fuel, spark) are also good.
If your compression is significantly below the recommended range, common causes include:
Worn piston rings
Scored cylinder wall
Blown head gasket (less common on small 2-strokes, but possible)
Crankcase seals leaking
This Chainsaw has some bad reviews online
https://www.productreview.com.au/listings/mcculloch-m3414-m3616-m3816-m4218-m4620-m3616Some people are just buying a new Giantz 62cc Chainsaw $135.with free delivery online as most shops these days
just want to sell people new saws.and won't fix older saws. and these McCulloch saws are usually discontinued making parts
more difficult to find.
As Bruce mentioned if compression seems a bit low," it's likely you have a compression issue that falls below the usable range. You'll likely need to investigate the piston, rings, and cylinder for wear or damage.
Cheers
Max.