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Miker-1

Tecumseh HH120

By Miker-1, in Engines

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Miker-1    1

Miker-1
Posted
On ‎12‎/‎19‎/‎2016 at 8:36 PM, tbarnhart said:

You're right, .020 is correct specs for the exhaust. The compression release will not open the valve very far. Probably only a few thousandths. Most likely the operating pin on the cam is worn. If the lift is less than the valve clearance, it won't open and the compression stalls the starter. That's why putting a feeler gauge in the gap makes it work again. You could try lowering the clearance to .015 and see how that works, but its not simply an adjustment. You're looking at one of the methods I described above. I have a 16hp ohv Tecumseh that has some of the same issues at times. Mine calls for .010 ex valve clearance, but I keep it a tiny bit closer to help the compression release work properly.

Would you know length of tappet and  exhaust valve. I measure .025 on length of pin on camshaft and measure about .004 lift on ACR stroke. I hope I didn't shoot in foot again! I seem to do that often

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tbarnhart    240

tbarnhart
Posted

No, I don't know the length of the original parts, but your measurements would seem to make sense. 0.025 of lift on the decompression mechanism with a 0.020 valve clearance would leave approximately 0.005 of valve lift for decompression. That is probably enough to get a small compression reduction, but may not be as much as originally intended. I would see if I could get that valve clearance down to about 0.015. You may have to build up the end of the stem with weld or lightly grind the valve/seat to lower the valve in the block.

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woodchuckfarmer    333

woodchuckfarmer
Posted

Id recut the valve seat or have the valve lightly reground before welding up the stem.    Wayne

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tbarnhart    240

tbarnhart
Posted

That's certainly the best way, especially if the valve sealing surfaces are a bit worn anyway. If it's all really good, or the valve is already thin, I've built them up with a hard weld deposit and never had any problems. I'm not looking at it, so I'm just trying to put all the options out there. Want to keep a good Tecumseh going.

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my new toy    2

my new toy
Posted
On ‎12‎/‎18‎/‎2016 at 11:35 AM, Miker-1 said:

If I'am filing valve wouldn't that give me less clearance. putting in feeler gauge increase's lift right. It makes  the ACR open more to reduce compression? Pulled head not much carbon.

I have a hh120 with the original engine it is a Tecumseh 12hp. I think they couldn't get Koehler engins for about 2 yrs. so they switched to Tecumseh Engines

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