# Tecumseh 10 hp compression



## montyrhody (Mar 1, 2005)

What should the compression be for a 1969 10 hp tecumseh motor? The compression in this motor is 60 psi. Does this sound ok? Thanks for your help.


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## roperdude91 (Nov 10, 2004)

thats low, pull the head, and replace the head gasket and look the cylinder walls, if you can see visible scratches or a ridge in the cylinder wall then you will have to get it honed
also check for burned,pitted or sticking valves, you have to turn it over by hand to check that
if the headgasket doesnt help if the cylinder walls and valves are in good condition, then you should look into a new set of piston rings


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## bugman (Aug 12, 2004)

my guess is bad sealing valves if its that old and if it hasn't been used much. if the cylinder wall most of the time it will look good but have a deep wear ridge at the top, this means honing it out 10 thousands over and installing 10 thousands over sized rings if it isn't worn bad. what is the engine on exactly?


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## bbnissan (Nov 7, 2004)

That sounds exactly like the 1970 Briggs & Stratton engine I fixed a few weeks ago. It ran, but it was really hard to start and the compression was right aroudn 60 psi. I checked the valves and found that the intake valve wasn't closing all the way. I popped it out, filed it down until it was back in spec and put it back in the engine. That bumped the compression up to 105psi and made it much easier to start. Not bad for a 35 year old engine :thumbsup:


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## bugman (Aug 12, 2004)

yeah thats what i am shooting at the valves. they must close fully and have a nice wear ring all the way around the back of the valve and the opening.:thumbsup: not hard to fix.


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## montyrhody (Mar 1, 2005)

How can I tell if this engine has a compression release. This motor is on a Wheel Horse garden tractor.


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## bugman (Aug 12, 2004)

it should have one.


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## scrench (Dec 8, 2004)

if you can crank it over backwards it will eliminate the relief , or do a wett dry check the compression then put a little oil in the plug hole and if the compression jumps up its the rings if it dont then more than likley the valves aint seating


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## bugman (Aug 12, 2004)

yeah you can do a oil down the plug hole to see if the compression jumps, if it does like scrench said it is the rings, but in the case of it not being a used much engine it might be the valves. if it is the valves you are in luck, because thats a easy to fix process. sometimes you can eliminate this easily, if its a horizontal the wear ridge will be all around and that will tell you, also if its a virtical the wear ridge will be more at top. also i'm wondering, are the plugs fouling not long after you put one in. because a valve would cause compression loss but many times not fouling, but a worn out bore and rings will cause fouling.


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## scrench (Dec 8, 2004)

does it smoke ? if it does it could be the crankcase breather ,the rings ,or the valve guides , also you can set the valve clearance without taking the valves out or taking the valve springs off , with a small flat file


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## bugman (Aug 12, 2004)

yeah i would also like to know is the plug wet, not with gas now, if its smokes black smoke its gas, usually oil smoke is white or blue, but is the plug wet with oil, if it is it just might very well be what scrench said above, most of the time it might be as simple as the valves being out of wack and if it smokes the breather needs replacing.


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## montyrhody (Mar 1, 2005)

For some reason when I re-checked the compression it was 115 psi. I was told this engine was rebuilt not to long ago. This mower isn't running yet, I just got a new coil and hopefully it will run know.


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## bugman (Aug 12, 2004)

may be that you didn't have the checker in right or etc. you didn't try it with oil down the hole did you?? if you didn't then you will be alright with that much compression. oh and try some marvel mystery oil, it'll help with rebuilt engines, put it in the oil and gas. you'll love it.


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## bbnissan (Nov 7, 2004)

Make sure the choke is off and the throttle is wide open when you do a compression check, otherwise the compression reading will be on the low side.


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