Struggling to run - 861

[_AndyA_]

I have an 861 and it was running OK last year but increasingly rich - more and more exhaust smoke. I then left it for five months over winter. When I returned all of the ethanol-free fuel had leaked out of the tank via the closed shut off valve o-ring. The sediment bowl was still full. I put some new fuel in, tried to start it and it wouldn't.

I converted it to 12V and the starter runs fine, so the engine turns over but it wouldn't fire up.

I drained the tank via the fuel hose to the sediment bowl, removed and replaced the shut off valve and removed and did the following to the carb (Marvel Schebler TSX-813):

• Thoroughly cleaned with carb cleaner, making sure all passageways were open
• Dried with compressed air, going through every passageway in both directions
• Replaced the float needle and jet
• Replaced the gaskets
• Replaced the main jet adjustment/drain (the original broke on reinstalling)

I bought the tractor last spring off a guy who rebuilt carbs for a side hustle and it was clear to me this one had been rebuilt, so I didn't replace anything I didn't feel the need to. There was some surface rust in the bowl but I cleaned it off. Throttle and choke plates were very clean. The sediment bowl had rust in the bottom and I cleaned that.

I put the idle needle back in exactly the same as it was - 1 1/4 turns from fully in. I put the main jet needle 1 1/2 turns from fully in. I don't know what the original was but I think it was almost or fully in.

The result:

• It will only start with the choke fully out (ambient temp is 65F to 75F)
• It will only start one try out of maybe 10
• It increases revs slightly and becomes less "pulsating" when pushing the choke in
• It will only start with the throttle about 20% off idle
• Revs are at or near the max
• Dropping the throttle to idle stalls it
• Increasing the throttle causes the revs to progressively drop and then it stalls
• Adjusting the idle and main jet needles appears to have no significant effect, the revs remain very high

So it seems to be running very lean? Fuel flow from the tank seems fine - I saw that when I drained it. I am thinking that my carb cleaning didn't achieve anything as it wasn't the problem.

I don't want to start messing around with the governor if it isn't the problem and going down a rabbit hole making things worse.

Any suggestions on what to check or try? I will do this next from @JMOR:

remove the carb bowl (not sediment bowl) drain plug and measure flow to see that it flows enough to fill a pint jar in two minutes or less

Thanks! Andy

 

[showcrop]

Before I start pulling things apart when anything doesn't start, I pull a plug or two and take a reading. You can tell a lot about what is going on looking at the plugs.

 

[Sean in PA]

Also check the quality of the spark while you have the plugs out.

 

[soaked]

Hi Andy,
There may be more than one issue to fix here.

Did you keep the 6 volt coil, and add the white ceramic resistor that often comes in the 12 volt conversion kit, or did you go with a 3.0 ohm 12 volt coil?

If ~1.2 ohm 6 volt coil, and a new ~3.4 ohm resistor, the total ~ 4.6 ohms may be dropping too much when the starter is engaged, giving a weak spark.

If yes, when starting, can bypass the resistor, keeping the tractors spade connectors on, and squeeze the jumper clips just above them. Once running, unclip the jumper.( both sides)

John

 

[_AndyA_]

Hi Andy,
There may be more than one issue to fix here.

Did you keep the 6 volt coil, and add the white ceramic resistor that often comes in the 12 volt conversion kit, or did you go with a 3.0 ohm 12 volt coil?

If ~1.2 ohm 6 volt coil, and a new ~3.4 ohm resistor, the total ~ 4.6 ohms may be dropping too much when the starter is engaged, giving a weak spark.

If yes, when starting, can bypass the resistor, keeping the tractors spade connectors on, and squeeze the jumper clips just above them. Once running, unclip the jumper.( both sides)

John

Thanks John. I swapped the coil:

https://www.external_link/FDS1106-Alternator-Conversion-Kit

The tractor ran fine after the conversion.

Andy

 

[_AndyA_]

Gas and oil on the two plugs I removed (Champion H12). Electrode completely gone on one of them.

This is a light-duty occasional-use tractor, mainly for maintaining half an acre around a building, so now need to look at pragmatic solutions.

I will do a compression test and replace all of the plugs with Autolite and report back.

Andy

 

[_AndyA_]

Compression results (fuel shut off, coil disconnected, all plugs removed):

1 = 142
2 = 130
3 = 140
4 = 130

I'm pretty happy with that. The compression testing killed the battery so it is now on charge.

Andy

 

[_AndyA_]

Charged battery, new Autolite plugs, started right up and runs smoothly.

I still have the issue of it being smokey and smelly. Tomorrow I will get it fully warmed up then try adjusting the main jet off idle to see if I can lean it out.

Andy

 

[showcrop]

Charged battery, new Autolite plugs, started right up and runs smoothly.

I still have the issue of it being smokey and smelly. Tomorrow I will get it fully warmed up then try adjusting the main jet off idle to see if I can lean it out.

Andy

As your owners manual tells you, you can't adjust the main jet without a load at high throttle setting. Just leave it at 2.5 turns as your manual tells you until you can put a good load on it.

 

[MarkB_MI]

If the carb is actually running rich, all of the spark plugs will be black. If only some of the plugs are black or wet, the carburetor is not your problem. Pull the plugs again and see what they look like. I suspect you still have one or two missing cylinders; this can be confirmed by pulling loose the plug wires one at a time while the motor is running.