Backwoods M Max
New member
So this has been playing in the back of my mind for a little while, and I wasn't able to get back to my notes until today.
Back in 2011 when I bought my mountain max I compression tested it when I put her away for the spring with the intention of doing it every spring. We'll I've never gotten around to checking it since but this is what I'm wondering? In May 2011 my sled pulled 140/135/137 pto/ctr/mag compression with 5300 miles on it. I have read enough forums where people have asked and the standard response of 115-120 for a healthy redhead has got me wondering, did someone peel the head gasket or base gasket previously? I know that there is variation in testers, hose length ect but what do the engine experts think?
I will admit 2-stroke internals and tuning is my weak spot, so that's why I'm asking. I have always run 91 octane anyways because of the manual requiring 88 and not feeling great about 89 with ethanol lowering the quality.
Back in 2011 when I bought my mountain max I compression tested it when I put her away for the spring with the intention of doing it every spring. We'll I've never gotten around to checking it since but this is what I'm wondering? In May 2011 my sled pulled 140/135/137 pto/ctr/mag compression with 5300 miles on it. I have read enough forums where people have asked and the standard response of 115-120 for a healthy redhead has got me wondering, did someone peel the head gasket or base gasket previously? I know that there is variation in testers, hose length ect but what do the engine experts think?
I will admit 2-stroke internals and tuning is my weak spot, so that's why I'm asking. I have always run 91 octane anyways because of the manual requiring 88 and not feeling great about 89 with ethanol lowering the quality.
an easy way to tell is to look at the tab that sticks out between the head and cylinder top, if the rivet is gone from the hole in the tab, the gasket has more then likely been peeled. The gaskets are 3 layers stock and yamaha puts little rivets in the tabs to hold them together.
you can also check the squish clearnace and youd know.
you can also check the squish clearnace and youd know.
Backwoods M Max
New member
I won't be able to look at the sled until Monday. What's your thoughts on those compression numbers? Has anybody pulled compression on a sled with a peeled gasket?
dsc577
VIP Member
my tester read 130 stock.140 after i put in a single layer