Compression

Fooling with a Troy built Tecumseh engine. Manuals say that you can't take much stock in compression measurements on single cylinder, small displacement engines.

However with a proven gauge I get 60psig. I think it's shot with that and since it blows a lot of oil....smokes pretty good.

The manual as stated doesn't give a number. What do you guys get for compression readings on small engines?

Thanks,
Mark

The reason you can't check compression and no spec is given is because most all engines use a compression release to aid starting. It bleeds compression at low speeds. Kohler recommends belting the old K series to another engine to get accurate compression results, they have to turn more than 200 rpm to disengage the release.

That said, I have checked a Kohler K341 at starter speed and got about 60psi, and that engine had a broken ring. I have two Briggs single cylinder 16s and they run 80 psi at cranking speed and both run like a top.

I have gotten 60 psi readings off brand new Briggs and Stratton Intek engines.

That said, you still need at least rings and maybe more in your engine because it sounds like you are getting too much combustion pressure in the crankcase.

Appreciate the responses.

I didn't see any compression relief mechanisms in the Tecumseh manual but the BS manuals mentioned some kind of easy start they use on some engines.

Their methodology was in the grinding of the cam shaft whereby preceding the regular cam operation of the valves there is a ridge preceeding one of the lobes, forget in or out, which is about 0.010" higher than normal and that's just enough to crack the valve open and reduce the compression. At cranking speeds the shelf makes a difference, but they said at 3600 governed rpm things are happening so fast that it doesn't affect the compression. They said on engines with this easy start feature you turn the engine over backwards and the shelf won't interfere with the compression reading......but they didn't give a number.

I popped the head yesterday, old flat head, and the cylinder was heavily scored. The thing that caught my eye was the buildup of oil around both valves both on top of the block and down inside the ports and all along the valve. This smells of worn out valve guides and may have been the reason for most of the smoking.

So, I just figured this old antique can just RIP. If the engine is worn this bad the rest of it will probably show it's age too and it would just be a case of spending good money after bad or bad after good which ever way that sayin goes.

Mark