# Old Tecumseh H70 Engine



## gsnod (Sep 2, 2013)

I've got an old Tecumseh H70 engine that was missing the carb, so I rebuilt one laying around the garage and put it on. I've not had this engine running, so I don't know what (general) condition it is in. Took it off a snowblower. Anyway, can't get it started...it sputters a bit and then dies, so I know it is getting gas.

I'm thinking either a sheared crank key, or perhaps valves that are (way) out of adjustment. 

Any suggestions or agreement with my thoughts?


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## AriensProMike (Dec 2, 2014)

Valves are not adjustable on that engine. They would be worn or partially stuck. Sounds like the issue would be more carb related based on what your saying. What carb adjustments have you made so far?


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## unknown1 (Dec 13, 2015)

Sounds more like a fuel supply problem to me too... that carburetor you put together probably needs to be re-checked and cleaned. 
When everything is an unknown quantity it's hard to be 100% certain but... if it splutters then you have at least some evidence confirming spark and compression... assuming that the spark is consistent and that the compression is consistent... that just leaves irregular fuel supply.


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## 10953 (Sep 4, 2017)

the valves are adjustable,just it's a big job, R&I the head ,R&I the valves, grind the valve stem till you have the correct spec.when dropped back in with out the spring , put the motor back together, only flat heads i know of that have built in adjusters are on the old kohlers


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## ELaw (Feb 4, 2015)

What others have posted about the valves is true: _adjusting_ then can be difficult. But... _checking_ them is very easy!

Start by removing the crankcase breather... you may have to remove the carb to get access. Inside the compartment under the breather, you'll see the bottom of the valve stems with springs etc. and the tops of the tappets that ride on the camshaft.

Then turn the engine over by hand and you'll see that at certain parts of the engine's cycle, the tappets/valves move up to open the valves. For each valve, rotate the engine until the valve is lifted to its maximum, then rotate the engine 1 more turn so the valve is at its lowest lift. At that point you can use a feeler gauge between the tappet and the valve to check the clearance.

I don't have the correct clearance values on hand but they should be able to be found with a web search. Offhand I'd say look for around 0.008" on the intake valve and about twice that on the exhaust. If the clearance is off so much the engine won't start, you might find it's zero.


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## cranman (Jan 23, 2016)

Pop the flywheel...check the magnets....clean the points, or replace....button it up. Check to see if runs on ether. If it does and the spark and compression is OK, order a new carb from e-bay for $12.


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## gsnod (Sep 2, 2013)

Had a couple of minuetes tonight after work to pull the breather off, and found that the intake valve spring retainer was not seated on the valve. So, I'll need to reseat the retainer which I can do. 

If the retainer is still good, this will be easy - if the retainer is broken, then Jackmels.........I'll be looking for one!


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## classiccat (Mar 1, 2014)

Removing the head (_for a complete valve job_) is almost as easy as removing the breather... unless you break-off a head-bolt in the process :biggrin: . (_i've removed a bunch...never broke a head bolt_).

Grab yourself a new head gasket.

With the head off, clean-up the carbon then lap the valves (_you need more than zero tappet / valve-stem clearance_).

You'll also get a good view of the bore...I mic the bore and inspect for deep scoring & a ring-ridge at the top of the ring travel.

I don't adjust the valve stems until I'm done lapping the valves since it closes the gap a bit.

Torque the head bolts to spec & in the proper order (_reference the tecumseh L-head service manual_). 

Retorque the head bolts after a few heating/cooling cycles (_when the head is cool_).


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