OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Tecumseh / Kirby Engines Compression test

How much compression should a TVS90 or TVS115 have to be considered servicable.


Do they have decompressors????


Cheers, Bob.

no decompressor as such but I would imagine they would have a similar thing to briggs and strattons easy spin starting.

Whats a good compression pressure to aim for??? I dont want to bother with them if its too low. Getting about 60 in one and 40 in the other. Bob.

Those sound rather low, Bob. Did you have the throttle open when you tested it? If so, the next step is to put a spoonful of engine oil in the plug-hole and repeat the test. If it increases noticeably, you will know what is wrong (or at least part of what is wrong). If it doesn't improve, you might need to take a look at the valve seats. You need to check the tappet clearances anyway.

Carbs off and clearances checked.

One came with the carb off, the other i took the carb off to get at the cover plate.


I pulled the head of the lower comp one, TVS90 with pressure lube, nothing looked out of place. No bad lip in the bore.


Im thinking that they might have to go in the Tecumseh parts pile. Not having much luck with the Tecumseh motors. Only been able to fix two so far.



Cheers, Bob.

Did you try the oil-in-the-plughole test Bob? I think if the tappet clearances are OK, the low compression pressures will be either worn rings or poor valve sealing, and both are probably fixable. Rings can wear out on those engines without a noticeable lip forming at the top of the bore.

Could well be the latter i think.

If it's just leaky valves, it doesn't cost anything to fix. You can normally tell just by looking at the valve seats: if they are black, they are probably not sealing. If you have a good contact mark the whole way around, they are sealing. Unless they are badly burned, you only have to lap them to get them sealing properly. Then check the tappet clearance, of course: lapping the valve removes metal, and that reduces the tappet clearance.
I always recommend doing the oil test before taking the head off, because once it's off, you can't tell if the rings are any good without putting it back on again.

Ive side lined the pair of them.

Did a couple of two strokes, they are easier.

I will get back to them.


Bob.