QuestionPlease explain the difference/relationship of ring seal, crankcase and exhaust sealing. Reason: I've got an echo chainsaw that I want to try and fix as a project. The compression is 60psi with 5 pulls. If I add a teaspoon of 30wt oil, I can get it up to 90psi with 5 pulls. I'm assuming the rings are shot or the cyls are scoured. However, I've heard there are other sealing issues with 2 cycle engines.
1. How do I test for crank case sealing? Are crankcase seals replacable?
2. Same question for exhaust sealing.
3. If my only problem is ring seal, are there slightly oversize rings available that would fix ring compression problems?
4. Are there ridge issues with 2cycles when replacing rings?
Your help/advice will be much appreciated......Johnny
Answer
pistons
A leak anywhere in the crankcase will affect the engine's performance, as the air/fuel mix is pulled through the crankcase.
Testing properly involves blocking off the intake and exhaust, and pumping 5-10 lbs. of air pressure and see if it holds pressure, the same for vacuum.
Normally, there is piston scoring, or melting, which pins the rings down, and there is the loss of compression. I have seen
however, just plain worn out rings, and in those cases, just replace them.
Most rings are held in position by locator pins, and the rings can
only be installed one way.
I snapped a pic of the pistons for an 028 I am working on, the left
one is the badly scored one, the right, the new one with only the bottom ring on.
