Low Compression Tecumseh H70 130003 - Snowblower Forum : Snow Blower Forums
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post #1 of 37 Old 02-12-2015, 01:44 PM Thread Starter
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Low Compression Tecumseh H70 130003

Good Afternoon,

I am trying to bring back an old snow blower. Its an Ariens snow blower with a Tecumseh H70 130003 engine. I have replaced the Carb, head, exhaust and intake gaskets, cleaned the valves; lashed and lapped them. Before i lashed and relapped the valves i got 88 PSI compression, however now i get about 60 PSI and the engine wont stay running at all. Before i got it running but at high speeds it would sputter and backfire, thats when i lashed the valves based on someones recomendations(exhaust to .012 and intake to ~.010) However now it wont run and my compression greatly decreased. Any help would be awesome.

Thanks,
Tim
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post #2 of 37 Old 02-12-2015, 01:56 PM
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Welcome to SBF Tim!!!

is that 60psi using the recoil? if so, that's not-terrible / not-great...on a starter, you could do better.

Did you coat the new metal head gasket? I've been using the Permatex Copper head gasket maker...2 coats is plenty. Also, make sure you torque to 200 inch-lbs and in the proper order...then re-torque after a few heating/cooling cycles.

For the bad running, have you had the flywheel off to make sure you don't have a sheared flywheel key...throws off the timing? It could also be that the carb just isn't set properly...I understand that it's tough to set it properly if it won't run long enough...I would try leaning-out the mixture a bit to see if it performs better. Idle-jet is in play when you're not under load & the governor is set properly; high-speed / no-load throttle position should be barely off of the idle throttle position. That throttle is probably bouncing around like crazy...again making it tough to tune.


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Last edited by classiccat; 02-12-2015 at 01:59 PM. Reason: Added carb stuff...
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post #3 of 37 Old 02-12-2015, 02:03 PM
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Hi gr
Welcome to the Forum. Make certain that your cylinder head bolts are properly torqued to 200 inch lbs( 16.5 foot lbs.). Also, recheck yor valve clearances. You lapped your valves. Did you check your clearances at top dead center with both valves closed? You are leaking somewhere. You need to retrace your steps. MH

1960 Ariens 45-10M
1961 Ariens 10M55
1977 Ariens 22000
1972 Ariens 10000
1990 Ariens ST724
1987 Toro 724
Murray Ultra 522
MTD Single stage
8 hp MTD hybrid plow
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post #4 of 37 Old 02-12-2015, 02:13 PM Thread Starter
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That 60 PSI is with the starter, was 90 with the starter. I had the fly wheel off when i rebuilt the magneto, and the key looked good. It was also stuck in there, couldn't pull it out with my fingers but didn't try with any tools because i didn't really need it out.
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post #5 of 37 Old 02-12-2015, 02:15 PM Thread Starter
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Quote:
Originally Posted by motorhead64 View Post
Hi gr
Welcome to the Forum. Make certain that your cylinder head bolts are properly torqued to 200 inch lbs( 16.5 foot lbs.). Also, recheck yor valve clearances. You lapped your valves. Did you check your clearances at top dead center with both valves closed? You are leaking somewhere. You need to retrace your steps. MH
I did lash the valves and lap the valves at TDC
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post #6 of 37 Old 02-12-2015, 02:25 PM Thread Starter
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Quote:
Originally Posted by motorhead64 View Post
Hi gr
Welcome to the Forum. Make certain that your cylinder head bolts are properly torqued to 200 inch lbs( 16.5 foot lbs.). Also, recheck yor valve clearances. You lapped your valves. Did you check your clearances at top dead center with both valves closed? You are leaking somewhere. You need to retrace your steps. MH
I didn't torque the bolts just did hand snug, but i was going to go get a new crank case gasket in case that was in, maybe i will get a new head gasket, (Ive opened it up like 4 times now) and try to torque them down.
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post #7 of 37 Old 02-12-2015, 02:26 PM
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Like I said, you will need to backtrack. Everything you did should have improved compression...or at least left it the same. You erred somewhere....most likely on your valves. Did you end up grinding your valve stems to get the proper clearances? MH

1960 Ariens 45-10M
1961 Ariens 10M55
1977 Ariens 22000
1972 Ariens 10000
1990 Ariens ST724
1987 Toro 724
Murray Ultra 522
MTD Single stage
8 hp MTD hybrid plow
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post #8 of 37 Old 02-12-2015, 02:34 PM Thread Starter
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Yeah I ground down the valve stems. The exhaust was at about .004 and the intake had no clearance.
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post #9 of 37 Old 02-12-2015, 02:53 PM
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thats a little strange that the intake valve had less lash then the exhaust to start with. I think .010 is a little big for the intake. You probably have a leaking head gasket. Replace the head gasket and torque to correct inch pounds and in the correct sequence.
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post #10 of 37 Old 02-12-2015, 02:55 PM
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http://www.asos1.com/tecumseh4hp/Tecumseh.pdf

Change out the head gasket and torque in proper order to specs. MH

1960 Ariens 45-10M
1961 Ariens 10M55
1977 Ariens 22000
1972 Ariens 10000
1990 Ariens ST724
1987 Toro 724
Murray Ultra 522
MTD Single stage
8 hp MTD hybrid plow
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