Briggs and Stratton 2HP model 60201 backfire

This engine is from an old Ariens cultivator. It began screeching badly at the end of last season. I pulled it out a week ago and realized that it was the clutch of the recoil starter that seemed to cause the problem. A clean up of the clutch and the balls seemed to have fixed it so I started the engine and let it run for a few minutes, everything seemed fine but then the screech returned. I realized I forgot to lubricate the shaft the clutch rides on so took it apart again, lubed the shaft, reassembled everything and now it will no longer start but will occasionally backfire through the carburetor. The plug shows apparently good spark and it is receiving enough fuel to backfire. I've checked the shear key on the flywheel shaft and it looks good. I've sanded the flywheel free of rust. I've even cleaned the carburetor jets and all seems good. Cleaned the plug (but did not change it yet). And still it does not run but only backfires. I must have done something wrong when I reassembled the clutch and rope assembly but I'll be darned it I can figure it out.

Any help would be greatly appreciated!

 

Did you pinch the spark wire when you reassembled the fan shroud onto the engine?

RR

 

No, I don't think I pinched the spark plug wire because I get good spark with the plug removed. Still, I just checked the wire in case I nicked it somewhere but it looks great. I even repositioned the wire in case it was arcing somewhere but I still get the backfire. Any other ideas?

 

Sure does sound like the flywheel key. How did you check it?

 

The screech is from the clutch sticking to the crankshaft. You would need to remove the clutch and clean both the stem of the crankshaft (the part above the threads) and the inside of the square clutch shaft. The crankshaft stem should be clean, dry and polished. Do not lubricate it, as that makes it sticky and will only attract future dirt and dust. The lubricant can also run down the crankshaft and get inside the aluminum cap/cover for the points and condenser, which is usually bad. You might want to disassemble, remove that cover and see if your lubricant found its way inside. if so, clean it out, as that area needs to be both clean and dry.

While you have the flywheel off, you can check that flywheel key.

 

Bingo and thanks to you both, Cheese and XSleeper. My original "check" of the key was insufficient. From the angle where I sat, I saw the key stock in the groove of the flywheel and "assumed" it was in the key way of the shaft too. Turns out it is rotated 180 degrees and only when I turned the shaft around for another look, did I see the actual shaft key way. DUH! I knew the timing had to be off but stared right at the key and check it off as good. As I tell my kids, "good judgement comes from experience, and experience from bad judgement"! Thanks for the tip and "experience".