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Discussion Starter #1
I'm looking for a little help here. Over the past year I have rebuilt the motor on an old Massey Ferguson 135 AG3.152. Everything has been replaced or rebuilt besides the crank and the cam. The head was even rebuilt by a professional local shop. I finally had the chance to start it and run it a little but I have hit on a problem. It fires right up, and even runs great at an idle or even at high RPM's. The problem only occurs once I put it under a load. It can be as simple as even driving it up a hill. It will start to stutter and backfire through the carb and loses all power. This is obviously even worse if I am trying to engage the PTO or pull something. I'm certain the timing is correct(checked and rechecked), and the points and condenser have been replaced with an electronic ignition, so no problems there. I've adjusted the valves twice to make sure that I hadn't messed that up. The carb is a brand new Zenith that is supposedly an improvement from the original with a new 1/4" fuel hose, sediment bowl, and filter.

At this point I am running out of ideas and places to check to try and fix the problem. My next step is going to be to replace the new fuel line and check to make sure that any blockages haven't occurred. I'm only doing this because I have read online that similar problems like the ones I'm having could happen if there was a lack of fuel. After that I am at my wits end. Please let me know if there is something I have missed, or if anybody has had the same issues and found a solution.
 

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Kish JD 318/420/430
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Have you checked manifolds, the exhuast system for issues (collaspe, plugging, nest, etc). What is the compression when it brings to this? How long of run time before it acts up, has engine come up to normal operating temperature? Have you checked the new carb (float/inlet valve, main jet)
 

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Discussion Starter #4
Have you checked manifolds, the exhuast system for issues (collaspe, plugging, nest, etc). What is the compression when it brings to this? How long of run time before it acts up, has engine come up to normal operating temperature? Have you checked the new carb (float/inlet valve, main jet)
The exhaust manifold and muffler are both new. There are no obstructions. I have not checked the compression of the motor yet, I was making the assumption that the new piston rings, new engine sleeves, and rebuilt head that it would have good compression. Do I need to double check that?

It will run fine all day long as long as you don't put a load on it. Idles fine, revs fine....at a cold start or at operating temperature. But the second you start going up a hill or (in my case) start using the brush hog, it starts backfiring through the carb and loses power...to the point that it will shut off.
 

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Kish JD 318/420/430
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You didn't mention all that was done, so now I'm with Mark on checking the governor out.
 

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Makes me wonder if the new electronic ignition isn't advancing properly under load. I would toss a timing light on it and then put a load on it while stationary (implement that uses PTO) and see if the timing is advancing.
 

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Discussion Starter #8
Governor problem?
[/QUOTE
Makes me wonder if the new electronic ignition isn't advancing properly under load. I would toss a timing light on it and then put a load on it while stationary (implement that uses PTO) and see if the timing is advancing.
I had been wondering about the advance myself, as well. What part controls the advance exactly? The electronic ignition still works off a revolutions based on a magnet, but this is something that I might check out.
 

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Discussion Starter #9
You didn't mention all that was done, so now I'm with Mark on checking the governor out.
I was under the assumption that the governor only controlled engine speed. I can reach high RPM's fine, just not under load. If this is incorrect then I will definitely be checking that out.
 

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I think a common assunmption is that the governor only limits the engine from over revving...it actually allows more fuel to the engine to overcome a load or hill to maintain RPM...it prevents the engine from getting bogged down
 

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Discussion Starter #11
I think a common assunmption is that the governor only limits the engine from over revving...it actually allows more fuel to the engine to overcome a load or hill to maintain RPM...it prevents the engine from getting bogged down
That might be exactly what I'm looking at then. I'm sure that I would be looking at more than just adjusting the rod length for the governor. I'll start doing some research to see what I can find. Is there anything in particular that I should look for in regards to adjusting/replacing in the governor assembly?
 

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