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Model 28S707 1149-E1

History
Ran when put away last fall
Forgot to turn off fuel and gas all ran to crankcase
Starter will now only spin engine with plug out


Have done the following
Drained oil/gas and replaced with fresh oil
Three different starters tried with same result as above
Adjusted valve clearance.. 004 Intake 006 Exhaust
Starter will now turn motor with plug in but backfires and will not start
Gas tank not currently attached.. Pouring small amount of fuel down throat of carb.

????????

How is the spark? What is the compression at? Backfiring thru muffler or back thru carb?

Spark is good.. Compression 150.. Backfiring through muffler.. Also have checked flywheel key and it's in good shape.

I know you already set valve lash but I think you should check it again. I would set both in/ex at .004". Not sure on this engine but many have a built-in compression release to ease the cranking. Be very sure on the exhaust adjustment. It stays open or re-opens momentarily when the intake is opening. If the clearance is too much it won't allow compression release and will hold exhaust emission and cause fumes in hot exhaust system to fire.(backfire) Try setting exhaust and checking in several spots as you rotate the engine to be sure. gregjo1948

Will do.. Just came in from checking again and it was a tight .004. It gives one heck of a backfire when choke is activated, then that's it. Will advise after checking gap at different rotation.

Checked gap at several stages of rotation to make sure .004. Same results.. One loud backfire from exhaust when choke is activated.

Could head gasket cause these symptoms ?

Take the valve cover back off, and take the plug out, and carefully watch the valves while turning the flywheel by hand. Also make sure that the valves
are both coming up to the same height when the rocker arm isn't touching them.

Did you replace spark plug?

Spark plug was changed... Went ahead and pulled head. The gasket looks in pretty good shape with no apparent blow by. Both valves appear to be making contact with seats. The exhaust is very gummed up with carbon and took some effort to extract from head. Will replace gasket, lap valves and see if that may have been the problem.. Anything else I might look for while head is off???

Could have been just a slow or sticking exhaust valve.

Hope that's it. Will advise when put back together

Thanks

UPDATE..

Cleaned and lapped both valves and replaced head gasket. Fired right off and sounded good until it sheared the flywheel key. Could not getting flywheel nut tight enough cause key to shear ??

Oh, yes!!!!

Thanks Fish,

Chart is showing 100 ft. lbs. Seems a little stout. Does that sound correct for 28S707 1149 E1?

Doesn't matter, tighten it up good enough to hold!!!!!!!

Runs like a new one. Believe the exhaust valve carbon build up was causing it to stick.

Thanks to all who responded.....

Glad to hear it!!!