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Discussion Starter #1
The old 4hp needs a rebuild I think, I've got all the ignition parts, I've replaved them befor seems like low compression?I can turn it over with my hand? Do I need rings, do i need oversized 10 or 20 piston? is it valve lash? it runs for 5 min then just stops, and had no power, (1973) is this something I can tackle do I need a machine shop? It's one of these I get parts when I can get up some money?
 

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Sounds like valve lash could definitely be a problem. Google "Tecumseh l head service manual" to find out how to measure and correct it if necessary.

Likewise, the manual will tell you how to check the ring gap. Needing rings is much more likely than needing a piston.

If you have the measurement tools or are able to take the engine to a machine shop to have measurements taken, here's the best process for those parts:
1) Remove piston & rings.
2) Measure cylinder bore for size and out-of-round - check against specs.
3a) If bore is worn and/or out of round, have it bored oversized and install an oversized piston and rings.
3b) If bore is okay, follow manual procedure for measuring ring gap, and if it's excessive replace rings with new standard-sized ones. If piston is excessively worn or damaged replace it with standard size, otherwise reuse it.
 

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Discussion Starter #4 (Edited)
Ok so off with the head and check the wall, if it's shinny hone it, if it's scrached or out of round bore it. So I'm looking at $100 or $200 to get that back to making power,
It was throwing 25 feet back in the day, and I neglected the oil ?
 

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Discussion Starter #8
Yes still working on this little pain in the a--, is it a good idea to just pick up some new valves and use compound on them or is it more complicated, I guess I have plenty of time to get this running now that the worst New England winter in history is over!!!
 

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Your on the right track if you need to keep it original, myself I'd pop a 99 dollar (this weekend sale) Predator 6.5 and and have a quieter more powerful engine on there. That is, unless it's a two shaft job, then the rebuild is the way I'd go as well.
 

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Just remove the valve cover, stick a feeler gauge under the exhaust valve...Any clearance when closed? If not, a quick head off, valve out and stem filed down, reassemble and you maybe surprised with new found power..!
 

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Just remove the valve cover, stick a feeler gauge under the exhaust valve...Any clearance when closed? If not, a quick head off, valve out and stem filed down, reassemble and you maybe surprised with new found power..!
That one fix has transformed 2 of my machines into like-new. Need a head gasket, muffler gasket, and 2 valve cover gaskets. These parts are cheap.
 
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