I just replaced the head gasket and intake valve seal. I had a stuck float valve and fixed that. I also replaced the muffler and muffler gasket. I set the valves at .005" when the piston was at past top dead center on the compression stroke when the piston drops 1/8" down from it's high point. Now the engine runs rough and backfires alot. This seems like a timing problem but I didn't change the valve timing, I didn't open the crankcase, and I don't see any way to change the spark timing. This engine looks as good as new. When I had the head off, the cylinder liner looked so good I could still see the original hone marks from the factory, there were no linear scuff marks on the liner that I could see. The valves weren't burned or pitted. I have a good spark and all filters and oil were changed. I'm stumped! Can anyone help?
2007-05-05 03:53:28 · 5 answers · asked by garyn 1 in Cars & Transportation ➔ Maintenance & Repairs
If this is on a mower, someone hit something while mowing.
There is an aluminum square sheer key under the flywheel to the crank shaft.
If the engine stops sudenly, the flywheel tends to cut the shear key in half and throws the ignition timing way off.
The shear key only costs about a dollar, but replacing it can be a challenge as the flywheel needs to be removed. As well as all the cowling around the engine.
ADDED:
Holy Cow, 16 HP single cylinder engine?
That bugger must realy vibrate.
The engine cooling air intake screen should come off fairly easily.
Then the fluwheel nut. (big nut) You may need a 1/2" air impact wrench
If you're able to get the nut off, look down the crank shaft and flywheel. You should be able to determine if the key has sheared or not just by looking at the small notch on both. They should be lined up.
2007-05-05 04:04:01 · answer #1 · answered by Mr. KnowItAll 7 · 1⤊ 0⤋
I think you might have a bent crank and that blade is off balance. Check and see if that blade runs dead level as you spin it. Remove the spark plug first. This sort of thing causes an engine to run rough.
On backfire, Chances are that is the magneto doing that. Im not sure if you have points on this thing, maybe not, but if you do, they can be oil laten or misfunctioning and cause a backfire.
Id pretty much rule out valves on this thing.
2007-05-05 04:31:37 · answer #2 · answered by James M 6 · 0⤊ 0⤋
Pull the flywheel and check the shear key. Also .005 sounds a little tight for a valve clearance. Did you get that spec out of a manual for that engine? If so, OK.
2007-05-05 04:11:19 · answer #3 · answered by Ron B 6 · 0⤊ 0⤋
I would remove the carb and clean it throughly and put a rebuild kit in it. If you had the flywheel off did you torque the nut when you reinstalled it? That flywheel is heavy and will shear the key just by starting the engine if it isn't torqued properly.
2007-05-05 05:14:19 · answer #4 · answered by renpen 7 · 0⤊ 0⤋
i would suggest getting a manual or contacting a repair shop
2007-05-05 04:04:36 · answer #5 · answered by smokey 7 · 0⤊ 0⤋