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Help with JD G

A

Anonymous-0

Well-known Member
Hi all I have a G that has problems. First off it has a distributor ignition, and the compression is around 11:1. I still am running the old kerosene manifold for now, the valves are set properly, it starts fine and have been running 110 octane fuel. The problem Im having is when it loads up hard it starts coughing as if it is running out of fuel then spark knocks as the rpms drop way down because of the missing. I have opened the load jets and played around but still does the same thing. Just seeking some ideas. Thanks and Ill add any info needed as people give opinions.
 
What are the plugs and how new are they? I've had the best service from Autolite 3116's....but I don't have nearly the compression you have.
 
If you have a choke linkage hooked to the carburetor, when it starts to detonate, pull the choke part of the way on which would reduce the air flow and richen the gas flow. If it stops detonating, then look for fuel delivery problems or carb problems. If it still does it to some extent, then look to use 116 octane fuel. Just because you say you have 11 to one compression doesn"t mean that the cylinder pressures aren"t still WAYYYYYYYYYyy too high.
 
What are you points gaped at. My 60 will not pull power set at 22thousand as book says. I gap them at about 18 and it does not spark knock and plows great. At 22 the spark knock as rpms decrease is terrible and no power, will not handle 3 BTMS. Have a 40 crawler , required gap 22 and will hardly start, let alone any power but gaped down to 17 18 same as with 60, will start and do required work like a new one. Try it you have nothing to loose . PS: I would like some one to EXPLAIN to me why this is. Both tractors run great, but not at required specks.
 
Hmmmm,.......well now I guess checking the fuel delivery is a good idea, then it that is okay I'd look into getting hotter ignition with some sort of hot coil and electronic ignition. I've heard that high compression and rich fuel charge need a real hot spark to ignite properly.
 
I found a DELCO dist with 50 deg. total advance. Have you check your timing with a GOOD timing light.
 
Things to look for. Gas cap not vented, restriction in sediment bowl, carb. not clean or restricted at needle & seat. Timing off. Set timing 25 deg. total advance. You have to get rid of that hot manifold. You need to read your plugs as to color. They have charts in back of spark plug books. High comp. you need a colder plug. High compression needs the best ignition you can get. With engines running 11-1 comp. ratio I have been able to fire the plugs with a Wico mag. Rebuilt perfect cond. Special HD coil. NO resistor plug wires Wire type plug wires soldered at both ends.
 
The reason you get spark-knock at 22 and not at 18, is think how much sooner the points are opening at 22. Next time use a timing light and check it out. If you retard the dist it will run just fine at 22. Although I favor running points at 18, and would leave it alone. Vic
 
Has your carb been modified? If it has been bored for more air now you need more fuel. There's a small hole in big but it carb under where load her bottoms out. Drill it to .055 and try it again
 
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