650G - Burning through plugs!

[BrianB938]

I am kinda new to this Satoh thing and have really confused myself...HELP!!!

I have had the carb rebuilt (professionally), replaced the fuel pump and done a complete tune up. The tractor performs fine, but after about an hour or so of use, the tractor starts to bog down and I have found that I am fouling plugs left and right. It think it is running very rich (based on the smell). I am in Wyoming at about 5500 ft in elevation. The carb was rebuilt in Virginia so I am guessing that it was tuned at a much lower altitude. How can I lean this thing out and keep from burning through spark plugs?

 

[mit]

there should be adjustments on the carb to adjust the air/fuel ratio.however dont jump the gun.is there a choke on the carb? check that if it is opening.check air filter for clog.before making adjustments

 

[BrianB938]

I have replaced the air filter and there is a choke, but it is functioning properly. It is a Nikki carb. How do I make the air/fuel adjustments to lean it out?

 

[Outlander]

Is the float level correct? Too much fuel in the bowl will cause mixture problems.

 

[SATOHBULL]

Does it smoke when running, esp under load? If so is the smoke blue or black? If it is black, it is rich. Usually a float level problem, or dirt under the needle. If it's blue you are burning oil and fouling the plugs. Normally oil fouling will look oily on the plugs while rich fouling with be fluffy black deposits.

If it isn't smoking and the fuel system seems to be the problem check again for something fouling the float, maybe rubbing on the bowl, or sticking somehow.

Also, check the plug heat range, if it runs ok, doesn't smoke etc, the plugs could be too cold.

 

[BrianB938]

It does not really smoke at all. The plugs are fouling flat black, not oily. How do I adjust the float level? I am using champion N4C plugs. I thought I might step up to a hotter plug. Any suggestions there?

 

[mit]

tough problem.to adjust the float you have to drop the bowl.dont think it is a gas problem though.check compression.see if it is within specs.oil may be seeping in from somewhere and fouling the plugs.is there a timing advancer on the tractor?maybe the hose is collapsing on vacuum.

 

[Eagleview]

The mixture screw is the one with a coil spring around it protruding from the venturi(not the throttle stop screw) . With the engine stopped screw this in until it's seated . Turn it back out one and a half turns , start the engine and leave at idle and slowly turn it in or out until the engine sounds sweet . You probably only need to go a quarter turn each way before finding this spot . You should use a vacuum gauge to find this sweet spot but you probably do'nt have one . There are other things that have been stated but this answers you question about how to lean out the mixture . It sounds strange that it does it after an hour , i wonder if it's boiling the fuel in the carby and forcing it into the engine . Does it have a bakerlite spacer between the carby and manifold ?

 

[BrianB938]

I don't know if it has a spacer. I have now adjusted the mixture screw and changed the plugs again. I could not tell any difference when I adjusted the mixture screw. I did step up to a slightly hotter plug. The tractor starts up and runs fine, but when at throttle, and not necessarily under load, the tractor loses power, the governor engages, it almost dies, and if I clutch it (so it is no longer under load) it will fire back up. What is going on here?

 

[mit]

sounds like you are having some kind of ignition problem.check the wiring against the schematic.if u have points and they are arcking escessively the wiring could be wrong.

 

[Eagleview]

I don't know if it has a spacer. I have now adjusted the mixture screw and changed the plugs again. I could not tell any difference when I adjusted the mixture screw. I did step up to a slightly hotter plug. The tractor starts up and runs fine, but when at throttle, and not necessarily under load, the tractor loses power, the governor engages, it almost dies, and if I clutch it (so it is no longer under load) it will fire back up. What is going on here?

Do you mean while it is being driven or while it is stationary when you say "if you clutch it " ? Does it misfire or backfire ? If so it could be closed/dirty points as stated , faulty condensor , earth strap on distributor base plate broken , hole rubbed in coil body which allows oil to leak out of coil . Please give some more info on the condition .

 

[BrianB938]

It will "die" when sitting still and when driving...if stationary, it will lose throttle, the governor will engage and it will fire back up. If driving, I have to clutch it to keep it from shutting off. It really does not misfire or backfire except when it is cold and it first starts up. I did also replace the coil, condensor and points. Could points gap make it do this?

 

[mit]

if your tractor has a fuel pump it would be a good idea to see if it is pumping fuel.you have to disconnect the hose going to the carb and crank the engine fuel should shoot out and stop then shoot out and stop.like pulse.the timing advancer may be in your distributer check it if it is moving freely and returning returning to its start position. check the points if it is pitted.recheck the wiring on the coil.check all grounds from engine to chassis etc.cant say for sure what is the problem if you dont start eliminating what you have checked.start with gas: check gas,gas filter,fuel pump,the carb is good.now check timing,points,advancer,cap ,wires,

 

[Eagleview]

Did this start happening after you installed the coil ? Have you got the polarity correct ? Yes piont gap can do this . Did you adjust them while they where on the cam lobe ? Check in the book if you have one , but about 15thou is about right for the gap .

 

[Bl8tant]

This all sounds very familiar to me. We didn't use our Bison much, and it repeatedly sat for long periods (2-3 months) without fuel stabilizer. Last year it started fouling plugs, running rich, then running lean, low power, sometimes required partial choke to run, poor acceleration, random dying, the list goes on. I tried mixture screw adjustments with no effect. New plugs, new wires, new points....still no effect. Finally I decided to remove the carb. and completely disassemble it. Turns out there was all kinds of crud floating around in there that would clog jets (causing issues) then when the crud passed things would improve a little till the next piece clogged something. The accelerator pump plunger was also shot (FYI- the acclerator pump also serves as a secondary fuel circuit so if it's clogged you run lean, if it's stuck wide open you run rich). I removed every jet and cleaned with solvent, compressed air, and wooden toothpicks (NO WIRE OR DRILL BITS). Put it all back together and she purrs like a kitten. Carb kits are easy to come by (but a little pricey at $90) and it's not a difficult job. Considering how much money you've spent so far (I know your pain), it would certainly be worth a try in my opinion. You may get lucky and just need a good cleaning without having to buy the carb kit.

 

[Bl8tant]

Ok, I feel kinda dumb as the first line of your post says you had the carb rebuilt. I got sidetracked reading all the other posts. But I still wouldn't rule out a fuel issue entirely. Collapsing fuel lines or perhaps something floating around in the tank. I had an old dodge truck that was acting up and after lots of head scratching, I dropped the fuel tank and discovered someone had decided to put a cellophane wrapper in there. It would float around harmlessly until it got sucked up against the outlet line.
I also "second" the post about the fuel pump.
Any chance that the tractor is overheating? Do you have access to a infrared thermometer? When the tractor starts acting up, take a reading on the top of the radiator and the hoses. If it's much above 180degrees, you have heat issues which can cause all kinds of trouble and/or help lead you to other diagnosis (including blown head gasket).

 

[BrianB938]

Okay...the saga continues...

The tractor does have an electric fuel pump...1-2.5 psi...checked the pressure and it is pushing 2.3 psi. The polarity on the coil is correct, I think. Pos is attached to the alternator and the neg side is routed to the distributor.

I started this morning in the garage...
1 - Changed the plugs again (to have a fresh start)
2 - Set the ponts gap to .015
3 - loosened the distributor to be able to easily adjust the timing
4 - drained the fuel and replaced it with fresh fuel
5 - replaced the fuel filter
6 - Set the mixture screw to 1.5 turns out from seat

The tractor would not crank. It did not sound like it was firing. I took off the distributor cap and turned the engine over. I could see no spark in the points. Dropped the gap to .010...still no spark. Dropped the gap a bit more and got spark. The tractor started up fine.

After a couple of minutes of running, I adjusted the timing as best I could (by ear). Things looked like they were licked...then the dying started. The tractor would randomly die. It would re fire sometimes if I did nothing. It would always refire if I choked it. I did backfire a couple of times when I choked it to refire.

The wires are okay...recently replaced. The cap is okay...also recently replaced. The points only have about 2 hours of use on them.

It still smells REALLY rich. This is what is really confusing me...it smells really rich and dies from what could be flooding, but to get it to refire, choking it works??? Should I go back to the thought of adjusting the bowl and if so, how do I do that?

 

[Outlander]

Is your distributor shaft running true? My old Allis was doing the variable points thing some years ago and it turned out that the bushing that bears the distributor shaft was worn to an oval. Would not hold timing nor point setting that way. Replaced the bushing and all was well. The check might be as simple as grasping the rotor end of the shaft and see if you can sense any lateral movement.

 

[SATOHBULL]

I did not notice any mention of changing the condenser, If you have not done so that would be the next step. Maybe even if you have changed it already.

The lack of spark at the coil at .015 and .010 sounds a lot like a defective condenser.

 

[mit]

try running the tractor without the gas cap.if the vent hole is clogged it could cause stalling.does your tractor has a fuel cut off switch near the governor?if so check the connections to it.