shawnm said: (quoted from post at 11:08:04 07/17/12) I'm trying to get a bit of a stumble out of my 340. At full throttle it has a miss to it every now and then. Maybe its normal for these old tractors?
Last year at my local pulls it fell flat on its face. It appeared to be a fueling issue but I ended up finding an broken spring in the dist.
Here is what I've done to it this year:
- New Zenith carb
- New points (gapped to .020")
- New condenser, rotor button, cap, Auto Lite plugs, wires.
- New fuel line
- New sediment bowl assembly
- Compression is 170, 180, 175, 160
- Valves adjusted to spec
What else can I check? Here is a video of it running. At 1:40 you can hear the stumble.
If the main jet is too big, causing it to stumble you would be able to throttle back slightly and the motor should pick up rpms. If your at mid throttle and it is stumbling, the problem could be that you are in that transition zone between the idle circuit and the main circuit and you have the idle adjusted improperly. If you open to full throttle and then to idle and it back fires your too lean on the main circuit.
Also forgot to mention that your problem may also lie with the compression ratio. There is more than 10% difference between 2 and 4 which can cause problems of this nature, especially at load.
This post was edited by Dodgeit at 12:12:53 07/17/12.
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