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Craftsman LT1000 with Briggs Intek 17 won't start, backfires. Engine model info: MODEL 311707, TYPE 0132-E1
CODE 990615Z0. I found the exhaust valve way out of adjustment, set both valves to .004, no luck. Changed coil because a mouse chewed the wire up, set gap to .010 and cleaned magneto, no luck. Poured gas in carb, no luck.
Removed ground wire from coil, no luck. Shop sold me the wrong spark plug so haven't changed that yet, but it looked good. Any ideas?

Laneman said:

Craftsman LT1000 with Briggs Intek 17 won't start, backfires. Engine model info: MODEL 311707, TYPE 0132-E1
CODE 990615Z0. I found the exhaust valve way out of adjustment, set both valves to .004, no luck. Changed coil because a mouse chewed the wire up, set gap to .010 and cleaned magneto, no luck. Poured gas in carb, no luck.
Removed ground wire from coil, no luck. Shop sold me the wrong spark plug so haven't changed that yet, but it looked good. Any ideas?

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Did you possibly hit something hard with the mower? If so, I know its a pain but maybe its worth the time to remove the shroud and pull the flywheel nut and see if the flywheel key is sheared.

If you accidentally put the magneto coil on upside down, then it wouldn't get fire either. Also you can sometimes get a new part and it too will be defective! Like the other mechanic said, go ahead and check the key to see if it is sheared by removing the flywheel.

I did hit something hard, but it was a few mowing sessions ago. Guess it's time to check the flywheel key, which I have never done. I already have the shroud off from changing the coil. Any tips on how to do this next part of the job? How do i keep the engine from turning, is the nut left hand threads, etc.

Laneman said:

I did hit something hard, but it was a few mowing sessions ago. Guess it's time to check the flywheel key, which I have never done. I already have the shroud off from changing the coil. Any tips on how to do this next part of the job? How do i keep the engine from turning, is the nut left hand threads, etc.

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If you have an impact wrench the nut will spin off quickly enough that you don't have to hold the flywheel down very hard. The nut will spin off counter clockwise (lefty-loosy). If you use a socket wrench it needs to be sizeable or use a breaker bar if you have one. You'll need to block the flywheel from turning by putting a large screwdriver or breaker bar into one of the teeth next to the coil mount. Once the nut comes off if theres a cup underneath it just lift it up and look underneath to see if the flywheel key is in the correct spot. If there's nothing under the nut then you just have to look underneath it at the top of the crank. There is a keyway cut into the crank that holds the flywheel key in place and the same on the flywheel. Inspect very closely as it's sometimes difficult to tell if a piece has been broken off. Sometimes it's VERY apparent and other times not so much. If you just can't tell for sure post a good quality picture and we can make a more informed decision together. If it is sheared we'll advise on how best to remove the flywheel and broken key and install a new one. Good luck and let us know what you find.

OK thanks, will let you know what I find.

This is just a thought. I know that the mag spark is really weak from hooking up an auto timing lite. If you know where TDC is you could rotate with a timing lite and observe spark relative to piston. Might save the effort of flywheel pulling?

OK, the flywheel has not shifted. I pulled the nut and can see the keyway is perfectly aligned with the slot on the crank. I'm out of ideas now. Only thing I haven't done yet is put in a new plug because the store sold me the wrong one. Getting back to the exhaust valve, when I pulled the cover a small disc had fallen off of the valve stem, goes between end of stem and rocker arm. I put the disc back on and adjusted both valves. Method I used was to turn crank until one valve was fully compressed, then set other valve to .004. Turned crank again and did the same to other valve,set to .004. Both valves open and close normally. New coil installed, also tried putting some gas in carb, it won't even try to fire at all.

Just got back from lawnmower shop with new plug, still doesn't work. I took plug out and held my finger on spark plug hole while cranking to check compression. Felt like almost no pressure. Beginning to think i have a hole in piston.

OK,think I found the answer. The exhaust valve clearance had a huge gap in it when I looked. I was reading that this can be caused by overheating, which causes the valve seat to come loose and get caught under the valve. It is commonly caused by a mouse nest built around the cylinder cooling fins. I did have a lot of mouse nest debris on the cylinder. This would explain the lack of compression and the large gap. Now I hope I didn't bend a push rod when I reset the valve clearance while the seat was still under the valve. Planning to pull head next. Could use some info on how to remove head, seat the valve seat and put it all back together.

Laneman said:

OK,think I found the answer. The exhaust valve clearance had a huge gap in it when I looked. I was reading that this can be caused by overheating, which causes the valve seat to come loose and get caught under the valve. It is commonly caused by a mouse nest built around the cylinder cooling fins. I did have a lot of mouse nest debris on the cylinder. This would explain the lack of compression and the large gap. Now I hope I didn't bend a push rod when I reset the valve clearance while the seat was still under the valve. Planning to pull head next. Could use some info on how to remove head, seat the valve seat and put it all back together.

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To pull the head you will need to do several things. The shroud needs to come off. The muffler will need to be removed. On alot of mowers there is also a heatshield around the muffler that will also need to come off. The carb will need to come off. Remove the magneto. You'll need to remove the valve cover and loosen up the rocker arms and remove the push rods. The steel rod is exhaust and the aluminum one is for the intake. Once they are off all you'll need to do is remove the head bolts and the head wil come off. Check the head gasket and replace it if it is damaged. The common method for setting the gap on the valves is to bring the pistion to TDC on the compression stroke. At this point, both valves will be closed without any pressure on them. In lieu of a manual I normally set my valves at .005 each. Hope this helps.