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MF35 Misfiring

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12-19-1999 16:56:07

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I have a 1960 MF35 with a Z134 gas engine.It misfires intermittently.I have replaced plugs,plug wires,dist.cap points,rotar button,condensor,coil,and voltage regulator.I retarded the timing,which helped for a while,but it has started "missing" again worse than ever.I would appreciate any help. Thanks,RB in North Carolina.

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B.C.

12-20-1999 07:45:45

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Re: MF35 Misfiring in reply to RB, 12-19-1999 16:56:07

1. Are you sure the wiring is sound in general? Could there be an intermittant short or break between the battery and the distributor, ignition switch and so on?

2. Are the plugs fouling? If so is it from oil (either learn to live with it or re-ring or rebuild) or gas (main jet too rich or excessive idling and light loads)?.

3. If the exhaust rockers are worn due to insufficent lubrication (as others have alluded to to) then it's possible for some exhaust to sneeze back through the carb.

All this assumes the fuel filter is working and there isn't a few flakes of rust above the sediment bowl messing things up.

From what you describe I'd look for broken wires or bad connections. When a Z134 is right it'll idle at 600 and pull good up through the PTO rpm.

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Morten

12-20-1999 06:16:42

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Re: MF35 Misfiring in reply to RB, 12-19-1999 16:56:07

Hi;

I had a similiar problem with my MF35 a year ago. It sounded like the firing order was wrong, or timing completely out of range. The problem was a leaky intake and outlet gasket!!! If you shine a torch on the intake/outlet manifold when it's dark, you might see smoke around these parts. That is a sign of a blown gasket.

Morten

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Larry

12-19-1999 19:31:14

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Re: MF35 Misfiring in reply to RB, 12-19-1999 16:56:07

If you haven't solved your problem yet and the weather is cool and humid some of these older engines will ice up in the carburetor,this will make them act like they are missing. If this is the case you should be able to see frost around the carburetor. I usually just shut it off for a while and let the engine heat thaw the carburetor. You can try and rig something to draw warm air from around the exhaust manifold into the engine.

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Richard

12-19-1999 19:19:27

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Re: MF35 Misfiring in reply to RB, 12-19-1999 16:56:07

Hi RB
Does it miss at an idle or at light load situations.Or under full load.I have a TO30 that would miss at idle with the timing advanced. Retarding it cut power and made the exhaust manifold glow red.This engine had been tuned as has yours.By chance I increased the spark plug quite a bit,and it made the engine idle good and not miss a bit.It starts very good also.Is used every day.
More info will help.
I can measure mine if you want to try this.
Good luck and Merry Christmas.

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Elmer

12-19-1999 18:22:42

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Re: MF35 Misfiring in reply to RB, 12-19-1999 16:56:07

I have come across this before where someone has done a complete tuneup and it still missed. Problem was they used automotive high tension leads and they have silicone core. Take them off and throw them over the fence and put on a set of wire core leads. This would solve their problem.

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GEO

12-19-1999 18:35:48

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Re: Re: MF35 Misfiring in reply to Elmer, 12-19-1999 18:22:42

Elmer is right on the wire. Also, I have learned that you can't always use what is shown to be the right spark plug anymore either. I have had to use the hottest plug available to run these older equipment on no-lead gas.

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Gerald J.

12-19-1999 20:21:07

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Re: Re: Re: MF35 Misfiring in reply to GEO, 12-19-1999 18:35:48

The general consensus on the JD pages is that Champion plugs are to be avoided. I know my MF-135 fouls them fairly easily these days. The last I looked closely in the Champion plug catalog it said they had "improved" the plugs for old tractors by adding an internal air gap to make them fire better in engines burning oil. I won't put Champions in my tractors again.

Other things to check, though harder to get at, are the valve settings and the wear of the rocker arm bushings. They are oiled through the rocker arm shaft and the end plugs are cork. After 30 or 40 years the cork rots and the oil pressure is relieved from the shaft so the rocker arms aren't properly lubricated. If they get to dragging hard, they can break the 3/32" diameter anti rotation pin and once the rocker arm shaft spins a bit it cuts off oil flow from below. Then things don't get better. MF doesn't have rocker arms or bushings. I made a set for my MF-135 last winter. I see that CT now has rebuilt rocker arm assemblies for sale.

Gerald J.

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RB:Thanks

12-20-1999 16:46:10

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Re: Re: Re: Re: MF35 Misfiring in reply to Gerald J., 12-19-1999 20:21:07

Thanks to everyone who offered suggestions.I'll give them a try and let you know the outcome. Thanks and Merry Christmas, RB in North Carolina

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