MF35 only idles (1963)

Jhapster

New User
I'm at wits end, started having a problem with engine running, thought it was carb first, spark looked good so did a carb rebuild and no help. Then replaced all spark parts, full tuneup with coil. After this it ran at first, then the problem was that tractor would intermittently run at idle fine and SOMETIMES run up to high RPM or sometimes sputter on a couple of cylinders over idle, and sometimes take off and run fine again. So spark was an issue at first. Replaced all fuel line, filters, took of carb again, everything looks fine, but still only running at idle, occasionally pick up a bit of speed but mostly just sputters at high er throttle open, Checked air cleaner, all good. Replaced all electrical wires suspecting an intermittent short, no help. Pulled valve cover, no stuck valves. Everything looks good, so I just ordered a new carb and an electronic ignition converter but not real hopeful thats the problem. When I go above idle throttle and is sputters, spraying starting fluid into the carb has no effect on it, good or bad, so its not starving for fuel. Plugs look like burning rich but cutting back power screw less than 1-1/4 turns doesn't help either.
 
For laughs do you have an extra condensor? Quality of them these days is poor at best. Last ignition set i did i went through 3 before getting a good one.
 
Trouble shoot then parts NEVER ever the other way around.
#1 make sure your spark is a good blue/white that will jump a 1/4 inch gap or more at the center wire of the cap and at all the plug wires.
#2 pull the carb drain plug and make sure you have a good steady flow of gas that will fill a pint jar in under 3 minutes.
#3 when was the last time you serviced the air cleaner??
#4 how does it run of you have the air cleaner tube off the carb??
#5 is the carb to gov linkage binding up some place or do you maybe have something in the carb in wrong like the venture or throttle butterfly??
Post back what you find
 
#1, Will try that...i generally just look at a grounded sparkplug spark
#2, gas flow is good
#3, air cleaner fully serviced last year and again just yesterday, but it was clean.
#4, Runs the same with the air tube in or out, also no change with starting fluid sprayed in carb body
#5, Gov. link & throttle linkage all work smooth, The intermittent thing where it runs sometimes just fine rules out something installed wrong in carb or plug wires.

I could try putting back in a spare condenser that worked before, I do save some for spares.

One odd thing, the center carbon button electrode inside the dist. cap seems to be showing wear already with only two days of use on it, I did have two good running days, and thats the part that made me think to replace all my wires, some were a bit knarly looking, but with all new wires, still same, haven't had a real good run in 3 days now, but still idles great.
 
How humid it is where you are?? Could be a bad rotor or bad distributor cap and it is has been humid and the cap is cracked that can cause odd spark
 
Well, a new carburetor didn't help any, Still idles only and sputters when trying to go faster.

I ran it about 20 minutes to see if warming it up would help, no different.

I advanced the spark and it ran faster, but still rough

I still have the electronic ignition kit to install tomorrow, I wanted to do the new carb first.

Did notice one odd thing, after 20 minutes of running, sputtering away, I noticed the intake manifold was very cold and sweating water like crazy. Its about 68F out and humid and I bet the intake manifold was down to 50F of colder by the feel of it. I never seen that before.
 
Cold intake is how it should be or you have problems. Atomizing of the gas causes temp to drop very low and is a fact of how a carb works. As for new cap and rotor where did you get them?? If form a place like TSC good chance that is the problem and China junk
 
(quoted from post at 21:29:43 07/29/17) Cold intake is how it should be or you have problems. Atomizing of the gas causes temp to drop very low and is a fact of how a carb works. As for new cap and rotor where did you get them?? If form a place like TSC good chance that is the problem and China junk


I had one of those rotors from TSC, it was arcing through the rotor to the distributor shaft. Some of the "new" parts are worse than the old, worn out parts.
 
Got them here at YTC, although I have been burned with parts from Atlantic, got a new fuel bowl shutoff assembly that was all messed up with crappy machining inside, from India, would not make a tight shut off, was able to reuse parts though and rebuild my old one, just more time..
 
My ignition coil is a 028569M91 is there supposed to be a resistor in this coil?

I just got a new one from YT and it has 0 resistance, ordered as a replacement for my 1963 MF35 continental gas engine

I got a new one also from a local NAPA store and brought in my old one, they asked if it had an internal resistor and I said yes, this one has an internal resistance of 3.9

The wiring diagram from my manual show no external ballast, so I have to get a coil with one inside , correct?

I was running it at idle only, all it will do with the ballasted coil, I swapped in the zero R coil to see what it would do and had it hooked up with a small 20ga jumper wire just to ground the body brackets, and when starting the jumper melted, I thought these things did not really need a ground to the coil body, could this coil fault to ground be the source of all my issues of only able to run at idle?
 
It depends on who you got the coil from, a coil with the same part number from different parts companies don't use the exact same coil. Some will be a internal resistor, some will need a external resistor. Whoever you get the coil from they should specify if the coil is internal, or needs a external resistor.
 
The label on the coil will indicate if it needs a resistor or not. Some modern coils will have fine print with the instruction sheet that came with it. The BSD coil i am currently using, for example, says that if you are using electronic ignition then no resister needed but if you are running points then you need to use one. The ones that are called "internally resisted" really do not have resisters in the conventional sense. They just have extra windings that will give the same effect so you don't need an external one.
What did you ground exactly? There should be no ground wire needed for a coil..
 
Big thing is are they China parts?? If they are good chance they are junk form the get go. I buy most of my parts form my local O'Reilly's auto parts store and most have a life time warranty to boot
 
Just for your info there is and never has been a coil with an internal resister they are just wound different to have more resistance simple as that. A coil should either in the paper work or right on it say no external resister needed or resister needed
 
Well, the saga is over after 4 weeks....

I put in the electronic ignition conversion kit, with the resistor coil and it fired up like a new tractor.

So the new points were just no good and perhaps both of the condensers I had, one old and one new.

So at least I got a lot of PM done in the process while I whittled away at the problem.

This Am I also got a new pressure tester and got 130-140 psi in all cylinders, I also got a new NAPA distributor cap and rotor, they fit on
with less slop in how the cap centered on the dust cover guide notches, just that made it run a little bit better before I finally put in
the electronic points conversion kit
 

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