8n starts, idles, but wont rev.

noweirdbeard

New User
Hey guys. I finally got my new old tractor running after rewiring it and converting to a 12 volt neg. ground.
Its not running very well though and its got me scratching my head.
I put new points and condenser, rotor, plugs, coil. The cap and wires looked ok so I didnt change those. Seems to have a good strong spark on my tester.
It was running with the old carb at first, but I figured that was my problem so I bought a new carb and it ran just the same .

Its starts up quick and idles ok, but if I try to raise the rpm it sputters and dies or pops thru the carb.
I bypassed the fuel tank and am just running a tiny aux tank.
Air cleaner is not hooked up.
Checked firing order, its correct.

I made a bad video of it if you want to check it out and see what you think.
https://youtu.be/c6oGGSjJc68
 
<iframe width="560" height="315" src="https://www.youtube.com/embed/c6oGGSjJc68" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
Noweirdbeard,Try disconnecting the exhaust pipe from the manifold,start it up and try it.Then put your Marvel OEM carb back on.
 
What did you set the points at?

Did you remove the plate and check the advance weights?

Have you checked the timing advance w/ a light ?


Is your old carb an oem M/S?
75 Tips
 
So the exhaust pipe was not sealing well with the manifold at first and leaking. It actually seemed to help when I fixed that.
I set the points at .025. I put some wd-40 on the advance weights and moved them around to make sure they were working. I also tried advancing and retarding the timing. It made little difference.
Not sure if the old carb is the original, but it looks old. I messed up the main bowl gasket taking it apart to clean , but I ordered a new one and will try the old carb.
I also sprayed some starting fluid around to test for vacuum leaks. I didnt find any.
I'm really scratching my head. :shock:
Im sorry i could not figure out how to make my video embed on here. I promise I'm a better at fixing stuff than computers. :lol:
 
Noweirdbeard,The idea was to run it with the muffler unhooked to see if the muffler is plugged up,which will cause it not to rev up.
 
(quoted from post at 19:25:00 01/17/19) Noweirdbeard,The idea was to run it with the muffler unhooked to see if the muffler is plugged up,which will cause it not to rev up.

I thought you might be on to something this morning when I saw the muffler was crushed in on the bottom where I could not see it.
I ran it with the open exhaust manifold and its still doing the same thing.
A least thats one more thing to rule out. :)
 
Front mount or angle mount distributor? I highly doubt your 12V switch-out job had anything to do with it running. "...won't rev..."? Does that mean when you throttle up you get no response? If so, is the linkage connected? Simply looking and figuring doesn't mean a thing. Do root cause problem solving. Old carb is most likely just fine, maybe needs a rebuild but not the root cause. If front mount, is the OEM Ballast resistor in the circuit? It is required regardless if OEM 6V/POS GRN or a 12V job. Is there an alternator? Are the generator and Voltage Regulator out of the circuit? Is the coil 6V or 12V? Air cleaner and/or gas tank are not the issues either. I suspect wiring is incorrect. Send me your M/S carb and I rebuild it correctly.

Tim Daley(MI)
 
Sorry! Its a side distributor. I put in a new 12 volt coil and not running a resistor.

Reaching around the back of the carb and slowly opening up the throttle it starts sputtering and breaking up and will stall if you open it past a 1/4 open.
Starts up quick and idles like a sewing machine.
I think the old carb is fine. I just need a gasket for it and I'll slap it back on see.
 
Boys I got her to rev! I set the points gap with a dime and that totally did it! I sure thank ya'll for the help. Its always nice to brain storm with other people about this stuff. :D
 
Di you lose your feeler gauge? You do plan on going back and setting them at the correct gap, right? Because they are now open more than twice as far as they are supposed to be. The point gap is .025 on a side distributor. A dime is .053. Do the math.
75 Tips
 
(quoted from post at 15:54:37 01/18/19) Maybe an ignition coil problem though? Maybe I do need a resistor? I will search the forum.
Maybe iit is the left front tire causing the problem. If it runs with that wide of a gap you have problems but it is not the coil or a lack of resister. I would go back and look at the flyweights, or regap to the correct 0.025" and try it again.
 
I read about the dime on this forum. Old farmers trick to set points in the field. Too wide a gap, but works.
Anyhow it was the lack of a resistor on the coil causing the issue. The impedance was too low without it. Now that I have 3.5 ohms its running good with a .025 gap.

Maybe this will help somebody else out. More helpful than y'alls rude sarcasm anyway.

Thanks to all who gave helpful suggestions.
 
I'm both old and a farmer and have better
sense than to set my points at twice the
gap that's required. Back in the day, we
used a matchbook. Run the emory cloth
through the points then use the cover to
set the gap.

Care to elaborate on impedance in a DC
circuit?
75 Tips
 
(quoted from post at 09:08:30 01/19/19) Should have installed EI on it instead points,
ould you care to explain how EI would have fixed a problem that was not caused by points in the first place?
 
All I was trying to say with the EI comment was unless he likes doing this stuff all the time, cleaning, adjusting
points change it to EI. Myself when I need to use my tractor, I like to just climb on crank it up and ride. For all
those worried about my comment you don't have to worry any more I'am done with this tractor site I'am not going on
here anymore. From the EI comment to telling me the e power steering I put on my tractor won't work, (works for me)I
have had enough criticism, so bye all.
 

Hmmm.. 109 posts and he's an expert. Seems like he is heading to burned up coil and points.
 

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