Small engine shaking too much when running, Why?

GoceKU said:
The frame of this generator has steel feet at the bottom of the frame, which leave deep scratches as it moves around, i'm very surprised so many of you think is normal, because the shaking is so bad i can't keep the extension cord plugged in the socket on the generator, i've used tape even that failed, i'm sure the phone with which i filmed it can't show it as in real life. I do drive diesels, not even the old mechanical diesels shake so much.
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i first thought you were running the engine alone on the floor -and of course it would dance everywhere. however i see it's in the frame (and it appears on rubber mounts) so i say YES that is unacceptable. i don't think anyone would accept a generator they have to chain down in three directions

timing, point gap, carb, are all immaterial.

you have, i believe, a rotating mass consisting of a crank, rod, piston and flywheel (and timing gear) (you stated you ran it with the gen end off)
i would think it wouldn't run well with a busted piston so
bent crank at flywheel end - easy check
bent rod
issue with the flywheel
it would be easy to pull the head and see how far the piston comes up - not an exact check of the rod tho'

my first thought would be a bent rod but i am here and you are there so that's just a guess.
 
GoceKU said:
I've taken the head off, one of the first things i replaced was the head gasket, here is a link: https://www.hobby-machinist.com/threads/old-gasoline-generator-repairs.66014/
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from those pics it appears the piston comes up enough. you said it did the same with the gen end off so it has to be somewhere in the rotating mass of the engine.
flywheel appears to have no damage, from the pic,. can't think of how the crank end could get bent while assembled with the rotor and the rotor stabilized with the end bearing. too far off and the magnets would be scrubbing the coil. my thinking it keeps pointing to piston or rod
 
I’ve rebuilt several of those engines. Timing of points is crucial. Along with air gap to magneto. For proper timing you need a DI reading piston position I believe .035 before tdc. Then you set points I believe .020. All these numbers are for a hs40.
If that motor has been opened up by a previous person there could be other reason for vibe.
You really should download the Tecumseh manual readily available has everything you’d need to do a complete evaluation to tear down.
 
This is really weird. There isn't much in the crankcase. Piston, con rod, crankshaft and camshaft. Perhaps a rotor oil pump. Did someone work on it and not time the camshaft correctly? There should be timing marks on the stator and and its mounting boss, then point gap at 0.020". Even if the wrong fly wheel it should affect the mass and not the balance since they are both balanced.

Is it running at 3000 rpm?

David
 
Had an engine like that on my big paint pump it had to have flat tires and be against something or it would walk off
 
As i've stated earlier, i've been thru every system on this engine and set it as per the service manuel, only ignition timing is untouched, i may need to make a jig to hold a dial indicator in the spark plug hole to time it as per the manuel.
 
Does your model have the timing marks on the stator mounting flange and its mounting boss?

David
 
David S said:
Does your model have the timing marks on the stator mounting flange and its mounting boss?
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Don't think so, service manual shows timing it with a dial indicator at 0,889 mm btc
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