to30 misfire

[steve-in-ga]

I've owned this to30 for over 30 years. its been converted to 12volts. it has recently started running terrible. its missing like crazy. I noticed when I pull the choke about half way out, it runs smooth again. so,
my first thought was it's a fuel problem. I took the fuel line off and opened the shut off and there is what I think is an ample flow of fuel. so I took the carb off and cleaned it and put a rebuild kit in it. still runs
terrible. I put a new carb on it and still runs terrible. I read on this forum that poor spark can cause this same issue. I swapped the points, condenser, plugs, wires, coil and it still runs terrible. timing hasn't
changed and there is no play in the distributor.

I'm at a loss. any ideas are appreciated.

-Steve

 

[steve-in-ga]

I forgot to mention that I've sprayed carb cleaner all around the outside of the head and manifold to see if it's sucking air and I cannot find a leak.

 

[ruschman]

Steve, did you try pulling plug wires to see if you can find the cylinder not doing its job. Perhaps a sticking valve???

 

[olddavid]

Did you check the fuel line itself for ample flow? Is there an add on filter in the line?

This one is a reach, and I don't recall of hearing of this on a tractor but is your exhaust pipe and muffler in good shape and open?

 

[RM-MN]

Misfiring is most often caused by poor condition of the ignition points. New points may or may not solve the problem. Look at the contacts of the points you installed. Shiny and flat are what you want to see but sometimes what you don't see is the real problem as a tiny bit of foreign material is still present and causes intermittent connection. Try opening the points and putting some brown paper (paper grocery bag?) between them, letting them close and then pulling the paper through to scrub off the foreign material. It may take a few times to get it all removed.

 

[olddavid]

(quoted from post at 07:03:44 10/21/23) Misfiring is most often caused by poor condition of the ignition points. New points may or may not solve the problem. Look at the contacts of the points you installed. Shiny and flat are what you want to see but sometimes what you don't see is the real problem as a tiny bit of foreign material is still present and causes intermittent connection. Try opening the points and putting some brown paper (paper grocery bag?) between them, letting them close and then pulling the paper through to scrub off the foreign material. It may take a few times to get it all removed.

If you can find one an ignition point file makes it much easier. Don't use any kind of sandpaper as the particles may stick to the point surfaces and prevent contact.

 

[Mad Farmer]

(quoted from post at 12:36:22 10/20/23) I've owned this to30 for over 30 years. its been converted to 12volts. it has recently started running terrible. its missing like crazy. I noticed when I pull the choke about half way out, it runs smooth again. so,
my first thought was it's a fuel problem. I took the fuel line off and opened the shut off and there is what I think is an ample flow of fuel. so I took the carb off and cleaned it and put a rebuild kit in it. still runs
terrible. I put a new carb on it and still runs terrible. I read on this forum that poor spark can cause this same issue. I swapped the points, condenser, plugs, wires, coil and it still runs terrible. timing hasn't
changed and there is no play in the distributor.

I'm at a loss. any ideas are appreciated.

-Steve

Check your fuel flow at carb drain plug.

The elbow going into carb, with a filter I assume that's been cleaned.

The float and needle/seat also have to be OK for fuel flow.

Look over your cap and rotor well. You can check each cylinder with a timing light quick to see if all are firing. Are all plugs clean/unfouled? Check your wires are on correct dist terminals.

 

[Jerry/MT]

What's the radial runout on the distributor bushing? Should be no more than 0.002 If that bushing is worn, the Z129 will run like a three-legged dog!

 

[jhwis]

Does it backfire at all?

 

[steve-in-ga]

No backfiring

 

[Bruce(OR)]

Cylinder balance test might be in order. Pull the wires and loosely place them back onto the plugs.
Fire it up and pull the plug wires one at a time. Engine should drop RPM evenly.
My favorite tool for doing that is a pair of nylon pliers good for pulling 120 volt fuses.
As you pull the wire off, you should hear the spark jump the gap to the plug. As you are determining cylinder contribution, hold the end of the plug wire to ground to keep the electrical system happy.
If you find a dead cylinder then you can do the comp check hot dry and hot wet.
Two dead cylinders? Crossed ign wires?

Wanna have fun? Fire it up at night and look for the glow of the plug wires. If the wires are junk, you can see the spark jumping to ground or the other plug wires. Another test? Jumper wire with a long shank screwdriver. One end to ground the other on the shank. Probe the ends of the boots where the plugs are. Slide along the plug wire. Any holes or splits will jump to the screwdriver.
Now if that screwdriver has a bad plastic handle, you eyes will light up with each short.
Question is, will you tilt before dropping the screwdriver or not?