Chainsaw Repair

I have found at 120 psi they start and run ok.
At 115 psi they start getting alittle hard to start.
At 110 psi down to 100 psi they become difficult to start or it may not start at all.
Below 100 psi down to 90 psi you might get it to start on priming it thru the carb and it will not run right and will probably die.
Below 90 psi I doubt that it will start at all. 

At work all I do is work on 2 cycle engines and if I find one that is hard to start off the carburetor and has below 120 psi I let the customer know that there is a major problem and I do not proceed any further.

I was working on a guys 272 Husqvarna. He tells me the coil is bad because when he runs it for a bit it just dies. So I listen to him and swap the coil, fire it back up and it runs but wants to stall. Its hard to re start. Difficult to keep running. I'm adjusting the carb and its way off where stock settings should be to keep it running.
So I decide to comp test it and the tester reads 100psi. I pulled the muffler and we have scoring on the piston.
New piston and ring installed, clean up cylinder, carb back to 1 full turn out on the H and L. Now she purrs like a kitten.
Lessons learned. Don't listen to the customer and low compression saws are hard to tune and when they get warm, they drop more compression and go below the required comp to run.

The really, really old Devils will start and run fine at 70-90 psi.  But, that is smack in the 'normal' range for 1958.

I truly believe they were designed to run on Coleman fuel in a pinch.