Farmall A Misses

First off here's my first thread:

http://ytforums.ytmag.com/viewtopic...p;postdays=0&postorder=asc&highlight=

I know it's been a while but I had some time to play today, which is rare (I should have kept at cleaning my garage but that can wait for another day).

Here's what I did. Replaced all the plugs with new one (Autolite 386, gaped .025), no change. So I warmed it up for 10 minutes or so on fast idle and checked the compression. Everything was 85 pounds across the board, which seems a but low to me but it was dead even. The plugs read all the same, ie looked brand new, but that's not a lot of running time.

The miss isn't even, so I don't think it's ignition.

The carb (Zenith) was rebuilt but it has the same problem it had before I rebuilt it, the idle screw has not effect on the engine no matter where it's set, that is it can be seated or run way out (4 plus turns) and nothing happens. I even had a spare screw, no help.

It's has to be the carb right? I sprayed it down with starting fluid and nothing happened so it's not an obvious air leak. I couldn't find any leaks around manifold either.

I think might pull the crummy old Marvel off my BN an throw it on to see what happens.

K

I thinking

Take a timing lite and clamp starting with #1 wire watch fire should not be intermittent then go to next wire and continue all wire should have fire steady no missing then going again. this will also check the wires and if you have a dist it can mean bushings are bad letting shaft wobble your problem isnt gas its fire. That doesent mean the new plugs are perfect not too uncommon.

(quoted from post at 15:18:10 08/05/12) Take a timing lite and clamp starting with #1 wire watch fire should not be intermittent then go to next wire and continue all wire should have fire steady no missing then going again. this will also check the wires and if you have a dist it can mean bushings are bad letting shaft wobble your problem isnt gas its fire. That doesent mean the new plugs are perfect not too uncommon.

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This is the third set of plugs, I'm 99% sure that's not the issue. I can check it my timing light though.

It's a magneto, not a distributor. The shaft seem nice and tight, seems that the shaft wobble is more of a distributor thing anyway.

Still though, what's up with the idle jet adjustment having zero effect on how the engine runs? That doesn't seem, something internal?

K

If the idle jet screw has no effect at low rpm the jet needs cleaning. It will not have any effect at all at high rpm, that is the way it is supposed to be.

(quoted from post at 19:49:02 08/05/12) If the idle jet screw has no effect at low rpm the jet needs cleaning. It will not have any effect at all at high rpm, that is the way it is supposed to be.

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I've had this carb apart 3 times now. It's been soaked, blow out with air, sprayed out with cleaner, more air, no changes.

K