D8 13A PONY TROUBLE

[crazytractor]

Well i finially got the pony runing , well momentarily. I replaced the spark pulgs, and condenser, and polished the rotor and points. And started after a few tries. it started loud, but very strong and smooth. I got to turrining the enging, and after about two minutes it started back firing really loud and then shut off. the pony motor trans was leaking oil from a gasket so i will have to remake the gasket befor trying again. I know it can either be fuel or timing, but it was running really good before it shut off so i dnt think it was timming. It was so hot this saturday here in south texas that i didnt even check if it ran out of fuel. I check my spark plugs and they were dirt after small run. they were new. who knows why? what kind of oil does pont trans use incase it leaks out while changing gasket?
 

[Billy NY]

Thinking about this, sounds like something is shorting, out of time or retarded, I've never used it, or fooled with it on mine, but there is a manual spark control lever which I assume is for advancing or retarding. For that fuel to detonate like that, has compression, fuel, cylinder loads up with fuel, there is a delay, then ignition or some darned thing, I've never had either of mine backfire, I would be cautious, don't want to break a piston ring or worse.

Where you are you should be able to use 85W-90, but in the winter, or cold climates, the old books said to thin it, but now one would use a different oil.

Just wondering do you have the serviceman's reference book for the tractor, there is information about the magneto and so on, might be helpful, but if not I can refer to ones I have for tractors with the same starting engine.
 

[crazytractor]

I have several service books but not sure if it has all info. My concern is. If it start quick and ran great for a while Why would it be out of time? It only started backfiring after a short while of running, And the it started the backfires. Can low or empty fuel cause this too?
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[dpendzic]

I would check the mag cap very closely---as it heats up the cap will expand some and may have fine cracks that open up and allow a misfire.
 

[Billy NY]

Low fuel or clogged sediment bowl, carb screen, would not run or shut off. I would think something is going on in the magneto or cap like was mentioned given it was running well prior to. The first time I really fooled with one of these starting engines, I had magneto problems, one needed to be rebuilt, I found another laying about in a shed where leftover parts from another D7 starting engine, might have been a bosch, finally had the timing right and a hot magneto working correctly, fired right up, but was burning oil/smoking excessively, fouling plugs, but was running without skipping or backfiring.

I was reading in an old D7 7M book, says the crank needs to be 25 deg past TDC and is the correct firing point, thats in the servicemans reference book for the starting engine, and about the same as I described in the last post, but I would check the mag, cap and so on, could be a simple fix.