TO-30 popping

tafossa · Jul 27, 2015

Hi, I'm out brush hogging the pasture and when my TO-30 is under load going uphill it starts popping, jerking, and backfiring. When it idles is sounds normal. Any ideas what to do, clean the carb? I opened the main jet from 1 1/4 to 2 turns, but no effect. The glass gas filter is clean. Any help would be appreciated. I tried reving and pulling the choke, but no effect. Thanks, Tim

1948jr · Jul 27, 2015

probably points and condenser

tafossa · Jul 27, 2015

thanks, it has electronic ignition.

Steve@Advance · Jul 27, 2015

Could be weak spark, plug wires, cap and rotor, coil, loose connection.

Backfire out the exhaust is typically ignition related.

Back fire out the carb can mean too lean, but pulling the choke rules that out. Might open the drain plug on the carb, see what kind of flow you get, best if you can check it when it's doing it, also catch what comes out in a clean glass, look for water and rust.

A steady, continuous popping out the carb under load can be an indication of an exhaust valve not fully opening, as in a flat cam. Can be other valve related issues, sticking valve, broke or weak valve spring.

tafossa · Jul 27, 2015

Thanks, it's very variable. Sometimes I'll fiddle with the jet and all's fine for 3-4 minutes and then its back to popping out the air intake and exhaust. I just opened the bottom of the carb and flow is restricted compared to when I opened the line to the carb. Is this normal or should the flow be the same?

Tony in Mass. · Jul 27, 2015

The dist shaft lock nut could be loosening up, changing the timing. I just time them by ear anyway, whatever spot works best at idle and wide open.
the gas comin out the bottom of the carb is restricted by the needle, so that's normal...

Steve@Advance · Jul 27, 2015

The flow won't be the same, there is a normal restriction where the fuel has to go through the float valve. As long as there is a stream, not just a drip, it's ok.

Have you got another coil you could try just for an experiment?

rvirgil_KS · Jul 29, 2015

Maybe a long shot, but what about your wiring harness. Old cracked brittle wires and bare spots along with corroded connections could make for an erratic power supply to your EI. The EI, being an electronic device wouldn't like that, it wants a relatively clean even supply. Also, what about your switch?

Bob Kerr · Jul 30, 2015

You might want to check the coil, If it is weak it may have enough umph to spark the gap under low cylinder pressure at idle but when throttle opens more air gets in and air is an insulator and it can't jump the gap. I battled with this for years on a 1924 Oldsmobile that some one had put a new coil on in the 60s but never drove the car much. Just didn't figure that coil would be bad like it was so I didn't change it. Ran fine at idle, but sputtered bad with throttle. New coil and she runs like a scalded ape!

tafossa · Aug 9, 2015

I just want to thank everyone for their help. I replaced the coil and it now works like a champ again.

TO-30 popping

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