Tecumseh horizontal shaft engine won't start

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  #1  
Old 12-29-13, 11:12 AM
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Question Tecumseh horizontal shaft engine won't start

Hi guys,

Newbie here and have been searching the engine posts for a similar issue I'm having, but found nothing close. A friend gave me an older Airens snow blower since it did not start. I know its from the 1960s since I have a similar looking one, but bigger. It also has an electric starter - the kind that plugs in with an extension cord. The first problem I found was the engine had no spark. Took off the shroud and saw the flywheel key was sheared off. Got a new key and put flywheel back on and now it has real good spark. Engine has great compression too. I think my friend used the electric start and the engine kicked back, thus shearing the key. I am now trying to pull start it, but no success. Popped a few times but thats it. Fuel system seems OK. Tried using ether to get it going but that didn't work.

Question: Could the shearing of the key cause the engine to go out of timing? Would that be the reason why it is not starting? I figured the points have to be OK if I got spark...but if it sparks at the wrong time it won't run. Right? Any suggestions?
 
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Old 12-29-13, 11:29 AM
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The key sets the timing to be in time by positioning the flywheel on the proper spot on the crankshaft so that it is in time with the opening of the points. The only way to get a small engine out of time is to move the position of the camshaft, which is impossible.

If you have a crisp blue spark that will jump a decent sized gap, then you have good spark. If the spark is weak, that's usually poor connection at the points or a weak condenser. Neither is "easily" accessible on a Tecumseh.

You say it "pops", so I'd suggest you go easy on it with a bit of starting fluid. Don't be afraid to use the electric start, assuming it still works. The flywheel was probably sheared by hitting a large hard object like a brick or something which would jam the snowthrower and kill the engine abruptly, kind of like when your lawnmower hits a tree stump or something. That's often how keys get sheared... from the abrupt stop.

People who don't know what they are doing usually screw up the carburetor settings, so if it doesn't start... that's probably the most likely scenario. Figure out what carb you have, what the proper amount of turns should be on the needle. And go from there.
 
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Old 12-31-13, 11:47 AM
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Xsleeper, thanks for your reply. I'm of the impression that if I spray some starting fluid into the carb, the engine should start and run briefly - that is if everything else is correct. When I say "pops" it does just that, pops. It does not run at all. I've tried adjusting the carb and that does not help. Before I give up on this thing altogether, I'm trying to figure out if the timing could have been messed up by the flywheel bumping the coil (coil is beneath it), which could have moved it. Since all I have is time invested in it so far, I'm going to call it quits if it is not a simple fix. I don't have the time or tools to tear the engine down and rebuild it.

I also suspect the key was sheared when he was trying to start it. As I said before, the engine has a lot of compression and I noticed it kind of locking up when using the electric starter. This is why I was only using the rope starter.
 
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Old 12-31-13, 12:50 PM
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Like I said, the "timing" cannot be changed, provided you've got the key in the right place. The armature air gap could only change if you loosen the adjusting bolts on the armature. If you haven't messed with them, then the armature to flywheel magnet gap has not changed and it should be fine. (.10 to .14... .125 is ideal) You already said it has "real good spark" so one would think that your no start problem has nothing to do with the points, condenser, coil, armature, air gap... or timing. It also would not be the kill switch if you have spark at the plug.

So either it doesn't have "real good spark" like you think it does, or the problem is elsewhere. One thing that would be easy to do is to clean the interior of the magnets and the face of the armature with emery cloth or sandpaper. After all these years there has got to be some rust there that could be giving you a weaker spark than what you think/need.

Does your carburetor have a float bowl and a choke? Have you remove the float bowl and determined if you have fuel in the bowl? Many times the needle will stick to the seat... no fuel. When you try to start it with starting fluid, you will get a pop, but when there is no fuel coming through the carb, it isn't going to run or even try to run.

I don't recall if that motor has a breather valve cover over the valve springs, but if it does you could remove it and see if you have the proper clearance between the tappets and the valve stems. Too much clearance might mean the valves aren't opening enough. But that would also be very unlikely. You could remove the head and examine the valves to see if there is excessive carbon... and remove the muffler to see if there is any sort of blockage in the exhaust causing back pressure, but those would also be pretty unlikely. Removing the head usually means it's a good idea to replace the head gasket- when the head goes back on you should torque the head bolts the right amount and use the proper bolt tightening sequence.
 
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