2012 E-TEC Low Compression on One Cylinder

[InFeRnO]

Hey guys just need a little direction or input. I have low compression on mag side, its sitting at 90 lbs and PTO side is 145. I have checked Reeds, popped head off and inspected pistons, cylinders and rave valves. Piston and cylinders look great but the rave valve on the mag side is very slow and lazy. Any body else see this before? Would the rave valves cause that low of compression if they are gummed up? The running issue that I was having was around 6500-6700 rpm and it had a very good bog. Full wot is a little boggy as well and it idles rough. Still has decent power though. Top End?


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[ippielb]

Sounds like something let go, not a skidoo guy but it sounds like your rings are tired. Better play it safe and inspect it. Sometimes being safe will save you from losing bearings and having to re-nik a cylinder instead of letting it grenade at 7800rpm on a big pull. Maybe even get away with just doing rings instead of a whole piston if your cheap.

When you do your compression test are you holding the throttle wide open? Your exhaust valves control back pressure after the gases escape the cylinder. What makes your compression is the up stroke from your exhaust ports up. And there's only two things that can change that, your head isn't sealing, compression tester wasn't screwed in all the way and bled a little pressure, or your rings are letting some blow by.

Take my opinion for a grain of salt. Good Luck.

 

[sir boost a lot]

the ecu should pick up any rave problems! and for the low compression id re test it and if its still low refresh the top end! and have the crank looked at