Tecumseh won't run past half throttle

[38racing]

Ok so I have the engine on the bench. First thing I noticed and this is new, that there was oil on the top of the piston. Not sure why and it wasn't there the first time I removed the head. Just thought I would mention that. At TDC the valve clearance was .010-.011 on the exhaust and .080-.090 or the intake. Manual say .040-.010 for both is the range.
I was told by a friend that also works on small engines I should at least lap the valves why I have everything open.

.080-.090 or .008-.009? .040-.010 0r .004-.010? My manual (692509) shows all H35 before and after 83 as .004-.008 on both valves. Same whether point or solid state ignition. What manual do you have?

https://outdoorpowerinfo.com/engine_spe ... e_gaps.asp

with clearance so large new valves are likely your only option. I see some on ebay.

[Arkie]

While you have it on the workbench, READ page 70 of the Service manual about if the magneto is the external type with points it will not run correctly if it has a electronic flywheel key. Ignor this if yours is the internal mag. (inside the flywheel)

I do not know for sure but I suspect the electronic key will allow the points flywheel magnets to be just little bit out of SPARK time as the magnets are entering the magneto even though you have all else correct.

Lots of oil on top of the piston is not a good thing. make sure it's not too full of oil. After I got the valves lapped and re-installed I would do a leak down test while it's on the bench (actually getting a leak down percentage leakage, not just listening to the air flow)) and I would also do a compression test when I got it bolted down, check the compression when the cylinder is clean and non-oily.
I suspect you have been flogging a good carb.

Is the magneto OUTSIDE the flywheel on that one?

I just look at your engine parts list and appears your magneto is internal inside the flywheel, therefore dis-regard the about about a flywheel key.

If you do not find anything seriously wrong and it's still doing the same thing pull the flywheel and install a $20 Magneto. I've seen magnetos do the same as yours is acting. (I've also seen a measley condenser have similar issues. Both indicating good spark until under stress of running.
I thing the part number for your may be
Tecumseh Magneto 611002

[Roadrunner123]

yes those are typo's . I messed up zeros.

[Roadrunner123]

do I have to be concerned with Keepers? I've seen video's of people taking out the valve without removing the spring and then reinstalling them without any mention of keepers. They had the exact same setup as me.
https://www.youtube.com/watch?v=tWH_mkUbMUE
this link shows exactly what I have and how he does it without a spring compression tool. I actually have the same tool he's using.

[bgsengine]

the keepers are what fasten the spring to the valve. you have to at least disconnect the keeper so the valve can come out, does not mean you have to remove spring (and keeper) entirely, but you'd have a hard time checking valve clearances, etc with springs still in the box.

[KE4AVB]

But is so much easier to remove those key hole keepers if you use the correct tool. Just got to make sure the key hole in the right to unlock the valve. Plus some engines especially OHV ones that I work on uses split keepers

And engine clearance should be checked the valve loaded by the springs. And having install the valves several times to progress of the grind will cumbersome otherwise. I had just done a Kawasaki valve job with the same keepers and I removed the valve 6x before I got the .006 max clearance.

[Roadrunner123]

reason I asked this was I saw keepers on a video that there are two halves of a keeper and the person put grease on them to keep them on the side of the valve stem so he could reinstall them. I wasn't sure if I had these two pieces in addition to whats on the bottom of my springs. Those two pieces looked like a pain to put back on.
I haven't had a chance to take mine out yet but will be doing that today. Need to buy a lap tool and some compound and the local Auto Zone first.

[Arkie]

Oil on top of the piston:

Inspect the intake valve stem seal (wiper), make sure the rubber still has life and feels snug (little bit of friction) when sliding on the valve stem. If it's dried out and not sealing (wiping) the engine will suck oil up the intake valve stem. Also check the valve guides. Since that engine looks almost new with maybe low hours of use I doubt if you find any serious valve train problems, but being the engine being old and not used much the intake wiper needs inspected AND make sure that a valve is not too tight in a guide and possibly sticking. (doubtful but good time to pay attention to all when inspecting)

See if the intake valve indicates maybe oil coming up the valve stem due to bad wiper, but a bad oil wiper won't keep a engine from running, just causes one to produce oil blue smoke and carbon on piston and foul the spark plug.
Also when you first start lapping pay attention to the lap ring on a valve and the valves seat. It should be at the same place all around the valve. If a guide or valve seat is cocked the valve won't seat/seal good when the engine is running. make sure a seat is not loose in the block. (not likely on that engine but needs checked)
Spitting back through the carb you mentioned as the engine is dying is suspect of intake valve erratic issues or spark timing changing. (firing with the valve partly open)
Also make sure the flywheel is still torqued down to specs while it's on the bench, (not loose)

You asked if you need to be CONCERNED about valve keepers. YES, especially the two piece wedge type type you mentioned that grease aids in the re-install. Your keyhole type are more user friendly.
Make sure your keyhole keepers slot is ok (inspect the keepers) and do a close visual of the Re-install and if ONE is still cocked little bit you will usually see such as compared to the other valve spring.

On a OHV (over head valve) engine the keepers are VERY important, valve going through the top of piston usually if they come loose.

[Roadrunner123]

Ok so I removed the intake valve and included a link to show the carbon on the underside.
I see no rubber wiper that you're talking about.
https://photos.app.goo.gl/FaiWfnB74nTufCyk8
There was on evidence of anything rubber being in there.

[Arkie]

Appears maybe your engine does not use a intake seal.

Does the valve face and seat look ok? (any burned hard pieces of carbon around the intake valve seat/fact?

Does the intake valve's guide and valve stem appear snug doing a wiggle test?