Lawn mower does not run smooth at higher rev

[durkinnj]

See video first part is max rev and second part is lowest rev. Also backfires. New gas, new spark plugs, new coils, cleaned carb.

 

[slomo]

Backfiring to me is a flywheel key that got sheered. Ignition timing is off?? Cam timing or a flat lobe on a cam or 2???

Sounds like one cylinder is dead.Something isn't right......... Sounds waaaaay off. No musical harmony at all.

Rocker arms, push rods and valve clearance need looked at.

 

[slomo]

The real experts will need your engine numbers to assist in the diagnosis.

 

[durkinnj]

The real experts will need your engine numbers to assist in the diagnosis.

Model 44s677
Type 0008g1
Code 160216yg

I don't think it's anything too serious because it does mow the grass just fine. And it doesn't backfire constantly just every 3 to 10 seconds. Just doesn't run the greatest.

 

[slomo]

What I see again is the throttle lever/linkage hunting at higher revs. Seems to smooth out at lower revs. Main jet needs to be cleaned out. NO drill bits required here. Simple solvent and some fishing line work great. Run the line through a couple 20 times LOL. Make sure the tank is CLEAN and you have good fuel delivery AT the carb. Dirty carb alert!!

Ignore for now, what I wrote way up top. Clean the carb first.

So now I'm thinking the backfiring is a lean mixture from a dirty main jet inside the carb.

 

[durkinnj]

What I see again is the throttle lever/linkage hunting at higher revs. Seems to smooth out at lower revs. Main jet needs to be cleaned out. NO drill bits required here. Simple solvent and some fishing line work great. Run the line through a couple 20 times LOL. Make sure the tank is CLEAN and you have good fuel delivery AT the carb. Dirty carb alert!!

Ignore for now, what I wrote way up top. Clean the carb first.

So now I'm thinking the backfiring is a lean mixture from a dirty main jet inside the carb.

Well either I don't know how to clean a carb or it's something else. I've taken the carb apart and cleaned it twice now. Used nearly a whole large can of carb cleaner on it. Just cut my grass. Looks good. Runs okay but still backfires and does the same thing where it can't find a sweet spot for the revs.

 

[bertsmobile1]

Well for a start, carb cleaner actually does not do what it says on the can .
Secondly the engine sounds to be out of time & out of tune + it is surging
So time for a full service
So the valve lash on both cylinders .
The remove the carb and clean according to the instructions found at outdoor power info
It also sounds to be a touch out of time so check the timing key in the flywheel
A visual should be fine
Both slots should align PERFECTLY to make a square

 

[durkinnj]

Well for a start, carb cleaner actually does not do what it says on the can .
Secondly the engine sounds to be out of time & out of tune + it is surging
So time for a full service
So the valve lash on both cylinders .
The remove the carb and clean according to the instructions found at outdoor power info
It also sounds to be a touch out of time so check the timing key in the flywheel
A visual should be fine
Both slots should align PERFECTLY to make a square

Okay I will do this. Thank you!

 

[bertsmobile1]

Remember that the engine has to be stone cold and rotated to the right position for each cylinder
Have a good look at the head / cylinder joint for oil dampness