Originally Posted by
1200SportsterRider
Yesterday as I was preparing the Saito 182 twin for a run today I thought that one of the cylinders was soft on compression. I pulled the left intake rocker cover and watched the intake valve open the close. I flipped the prop, the left felt normal. The right did not feel right. I pulled the left glow plug, then the right felt normal. The compression strokes are so close together,180 degrees that the right cylinder feels, "funny". I checked the timing of both cams, they are correct. No leaky valves so all must be well.
A bit odd. Are you sure the throttle was open?
I've observed similar weak/mushy compression on glow engines that have sitting around for a while. The rings can get gummed a little but after a bit of running the snappy compression returns.
I'll be tearing down my preowned 220 for inspection tomorrow. It's down on power, turning a Xoar 18x8 at only 7400 on gas. It should be turning a 20x8 at near that same rpm. Bearings are smooth, valve clearances are correct, valves seal tight, timing is correct but compression is mushy and not improving with run time. Even though it was only bench run when I got it the thing wreaked of castor. It may have a stuck ring. I may just order an RJM ring for it since I'm right there anyway.