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Chris727

Tecusmesh timing

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Chris727
Hi. I a tecumseh HH120 on a 1968 Sears. It was running very erratically, even after trying several working carbs on it. This was after I had a guy do a valve job. The valves had too much clearance, almost 2 times what its supposed to. This is unusual right? Usually its too little and they need to be ground. I removed the valves and measured them up to some other HH120 valves and these are not too short. They should have plently of length. So I figured it was the cam or tappets which were the problem. I opened up the engine and like an idiot I forgot to check the timing match marks on the cam and crank before I removed the cam. Now here is my main question. A guy once told me he thougt some of the HH120's with starter generators had the timing mark advanced by a tooth so as to have compression release. Does anyone know if that is right? It does appear to have a mechanical compression release on the cam. Thanks in advance. Chris

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D-17_Dave
If it's missing any legable timeing marks, you might go by this. Every single cyl. engine I have ever seen the valves were open the same amount when the piston was at TDC on the dead or exhaust stroke. I have seen some tech. engines with the mech. comp. release but have NEVER heard of setting the timming off for any reason. On these small engines even 1 tooth off changes the timeing very dramaticly. High performance race engines only change the timeing a few degrees. Changeing the cam a tooth would probably jump it as much as 10 degrees. Or you could get smart and boat anchor it and replace it with a Briggs. JMO.lol

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Chris727
quote:
Originally posted by D-17_Dave
Or you could get smart and boat anchor it and replace it with a Briggs. JMO.lol
Dave, I'm going to sell this one so thats not really an option. But I'm not tecusmeh's biggest fan. Thats why the Suburban I plan to keep is one that came with a 32000 series 14hp CI Briggs from factory.So for now I need to fix this up as it is. I had been looking at my Massey service manual which covers the HH100 and 120 used on the MF10 and 12 tractors. It had said the valves were both supposed to have .10 clearance. I guess it was wrong because my tecumseh manual calls for .20 on the exhaust and .10 on the intake. So in reality I didn't have so much of a problem with clearance as I had thought. It may not be off at all, I won't know till I get the valves back in. BLT, it did start acting very funny after the valve job. The head had also been milled at that time. After first getting the engine back and putting the head on, I got it to start but wouldn't run smooth. The head was leaking around the edge by the intake valve. I checked with a straight edge and the head is ok but the cast iron block is off just a little from side to side. I know the head was drawing down tight. I had torqued them in sequence several times also had cleaned the headbolt hole threads up with a tap prior to installation. I'll put it back together with the cam timing mark and crankshaft mark lined up as normal. I have also decided to try using two new head gaskets and some head gasket sealer to make up for any inaccuracies in the block. I need to get this thing going good enough so that it can GO and make room for an AC. Thanks for the tips. Chris

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