F100 Won't start, need ideas

S

Supernaut

Member
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
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