56 massey 50 spark plug question

Victoryrider · Jan 18, 2019

I recently purchased a 56 massey ferguson (harris) 50 gas tractor with the z134 continental engine. I want to give it a tune up but I'm having trouble finding info on the correct spark plugs for it. I pulled champion d21 plugs out of it and crossed referenced them to a 386 autolite plug but the tractor sounds like it hates them. Misses and sputters at low rpm and sounds like it knocks now. Never been a fan of champion plugs but this being my first tractor I'd like a little input on what this engine requires. I cannot seem to find it online. Any help would be appreciated

John Deere D · Jan 18, 2019

How did the engine sound and run before you changed out the plugs and what ever else you changed?

Bob..

Victoryrider · Jan 18, 2019

It ran decent once it started. Took a bit of turning over to get started at first but after it did it ran pretty well. The plugs were rusted and oily so I wanted to replace them. The tractor looks like it hadn't been cared for very well so im trying to fix her back up. Once it started with the champions it pulled pretty hard with none of the knocking sound the these autolite plugs are doing.

Victoryrider · Jan 18, 2019

I looked up info on both plugs. The champion d21 plug is a non resistor, non projected plug. The autolite 386 are resistor plugs with short type projection. But they cross reference as compatible with one another. It's confusing to say the least. That and I believe the champion is a much hotter plug than the autolite]

Steve@Advance · Jan 18, 2019

I doubt the plugs are the cause.

Were there other changes made, like the points, condenser, timing?

Victoryrider · Jan 18, 2019

Not that I changed, no. I believe it has a factory 12v system with a modern alternator. But it was all on it when I purchased it

Steve@Advance · Jan 18, 2019

I believe it would have been 12v factory.

Might take a look at the distributor, those are known for the shaft bushing to have wear, causing the points to not stay set. Also the centrifugal advance should be free, it should turn slightly and spring back. If stuck or slow to return the distributor will need to come apart and be serviced.

Another common problem is a clogged air filter mesh. Usually it can be rinsed out with solvent, but if severely clogged it will need to come out and be replaced, or cleaned if you can get it out in one piece.

How's the fuel system? Rust in the tank? Good flow through the carb? There is a drain plug on the bottom of the carb, you can check the fuel delivery, it should flow a steady stream, not slow to a drip. The fuel should be clean, no water, minimal sediment.

Victoryrider · Jan 18, 2019

I checked the distributor when I got home today. It does return freely. Inside the tank is very clean, surprisingly. I will check the drain on the carb bowl tomorrow though. The sentiment bowl is a bit dirty now though. So I'll clean it out, then check the carb bowl for fuel delivery. I started for just about 2 minutes today and then died and haven't been able to get it started since. I will check the power to and from the coil to make sure it's getting 12v to it. Today is the first time it's done this. It could very well be what the issue was all along. Weak spark from a failing coil

WGM · Jan 19, 2019

It's amazing how Champion spark plugs and ethanol fuels get blamed for everything.

ASEguy · Jan 19, 2019

If the problem ONLY started AFTER the plugs were replaced is it possible you have crossed a plug wire or dropped a plug and closed the gap?

56 massey 50 spark plug question

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