Overhauled Z134 TO-35 miss /sputter

[TMU58]

I just completed a 100% overhaul of my Z134 - new liners, pistons, timing gears, ground crank, new camshaft, rebuilt head with new valve guides, new valves, springs, plugs, ignition harness, etc. I set the timing to 6 degrees per manual, installed rebuilt carburetor and was disappointed to hear a repeating miss or sputter at anything above a low idle. Advancing or retarding distributor hasn't much effect, nor does adjusting carb mixture.

Any guesses? I'm hoping it's just a coil or condenser, but those components are pretty new too...
 

[shaeff]

Have you tried narrowing the miss down to a specific cylinder? That's usually where I start.

Idle it up until the miss is apparent and audible. Use well insulated pliers to pull one plug wire at a time. If the miss gets worse, put that wire back. Work your way down from 1 through 4. If you pull a wire and there's no change, you've found your misfiring cylinder.

Now narrow it down to the plug or wire. Swap the wire out with a different cylinder and see if the misfire chases that wire. If not, swap out the plug. If the misfire chases the plug, grab a new plug for it.

Check spark on each cylinder too. You want a nice, fat blue spark that makes an audible *snap* sound and look the color of lightning.
 

[J.Wondergem]

Another thing to recheck would be the valve settings.

This post was edited by J.Wondergem on 07/12/2021 at 07:17 am.

 

[themikemix]

Check the carburetor float level, it should be set to 1/4 between the gasket and the bottom of the floats. A float level that is set to low more than 1/4 will cause a lean condition. I'm not sure why but every tractor I've ever worked on that runs poorly has a carb float level that's adjusted wrong. Mike
 

[restogreen]

Just has same phenomena on my 64 MF35 with z134 cont 4cyl engine.


Tractor would run few hrs bush hogging and start missing and acting like a plug was fouled or acting like the fuel was vapor locking . I would clean gas sediment bowl and tap carb with (tbd) and tractor would run.
Took carb (Marvel S.) off and OK. Float adj OK

I FOUND the brass inlet fitting was clean / screen was clean but was restricted by fine ??? in the elbow part of the brass fitting that would seem to lodge or loose .. preventing full fuel flow to the carb. (FOUND THIS by blowing in fitting which was restricted!!!!)
After I cleaned out the passage and rinsed /back flushed with brake clean/air I reinstalled carb.
AMAZINGLY I noticed that the Hi speed jet functioned better as now you could adjust for a true rich or lean setting. Idle jet as well
could show affects of adj (opt 1 turn out roughly and fine tune at engine idle ie 750-800 ERPM) Main jet about 1.5 turns out and fine tune at ie 1800 ERPM

I bush hogged on 90 deg high humidity day for 6 hrs and no problem.
Restogreen Arkansas
 

[BIG1RED9]

Check the flow of gas to the carb and the gas filter/screens.