F100 Won't start, need ideas

[Supernaut]

I have an old lawn boy that I'm trying to get running for the year but its just not happening. I took apart the carb, inspected it and reassembled it. Set the adjustments according to the manual and pulled and pulled the cord to no avail. Not even a single combustion event. I started tweaking the altitude adjustment and the governor but it was all for not.

Last fall this mower broke the throttle shaft and ran ungoverned for 2 min. I jury rigged it back together and the next time mowed my lawn. However it came apart and ran in an over speed condition for maybe 5 min. After this I borrowed the nice old lady's mower next door for the final 2 sessions while I was waiting for a new shaft for my mower.

I have spark. As far as I can tell the carb is the way it should be. The only other thing I could think of is damaged valves or crank case seals? Maybe the ignition came drastically out of time some how? Any other thoughts?

I think I'm going to buy another cheap used mower so I have something working in the mean time till this is figured out. There are some in the Edmonton area for $50 give or take that claim to work properly.

 

[Fireman 123]

The flywheel key could be sheared, causing it to be out of time. I doubt the reed valves are damaged. Have you tried spraying fuel mix directly in the combustion chamber? Seals could be bad causing insufficient compression to run. Good luck.

 

[turfboy1997]

I'm with Fireman. I think its the flywheel key. i bought a 7271 a few months back and it had a flywheel key sheared. i pulled and pulled and nothing. i changed the flywheel key and it fired on the first pull. It has very low hours because they gave up on it after they couldn't start it. i got it for $5 but it was missing the handle and the BBC cable was cut. i purchased those two items and i have a almost new mower minus the deteriorated paint.

 

[Supernaut]

I got a replacement key for the mower. Once I took it all apart and the flywheel off I was kind of disappointed to find that the old key looked perfectly fine to me. I changed it anyway and put it all back together. I sprayed out the carburetor with carb cleaner and put that together. Then when I pulled the cord it started right away. I couldn't believe it.

 

[Supernaut]

Bah! Well this isn't all so cut and dry. Tried to start it again and its back to square one without a single pop. At this point I think the thing might as well be rebuilt. Yesterday I think I just got lucky when it started. Just the right amount of fuel in the carb, wind was blowing the right direction, planets were aligned and I held my mouth just right.

One thing I would like to be able to do is modify it so that the engine could be started using a cordless drill. I don't see a real practical way to do that however.

 

[Fireman 123]

May be a silly question, but have you sprayed fuel-mix directly into the carb opening, or cylinder to see if it starts? Ignore this if I asked earlier. You say it's a F100, which is an older engine. It should have the same on/off switch as the old D series. Make sure you check every wire connection. Then check it again. Also check the plug wire for good connection at both ends. I bet this is something small. I personally wouldn't rebuild it unless it has very low compression, and then seals may be all you need. Good luck.