Craftsman Tractor Problem

[brian]

I have a Craftsman DYT 4000 tractor with a 21 HP Briggs V-Twin. There is some kind of a problem with the engine. When the engine is running with blades off it sputters and backfires. When blades are on it runs smooth. I have replaced air filter, fuel lines, fuel filter, plugs and cleaned out the Carb. There is no sign of water in the fuel. Also there are times it will bout die when coming off a hill, then blow a puff of black smoke. Could it be the fuel pump is going bad? Any help is sure welcome.

Thanks in Advance

[dpb]

Running too rich -- first choice is choke isn't opening fully so it's running partially choked, therefore a rich mixture. If that's not so, then there's a carb problem.

[trainfan1]

brian wrote: > I have a Craftsman DYT 4000 tractor with a 21 HP Briggs V-Twin. There > is some kind of a problem with the engine. When the engine is running > with blades off it sputters and backfires. When blades are on it runs > smooth. I have replaced air filter, fuel lines, fuel filter, plugs > and cleaned out the Carb. There is no sign of water in the fuel. > Also there are times it will bout die when coming off a hill, then > blow a puff of black smoke. Could it be the fuel pump is going bad? > Any help is sure welcome. >

dpb wrote:

Or the idle mixture needle is set too rich.

Rob

[dpb]

I'd classify that as a carb problem... :)

[brian]

It does seem to run smoother with the choke on just a little, if its not choked it sputters and backfires, if its fully choked it just dies. I've took the carb off and everything look fine. (This is the second carb i've put on it)

[Oren]

Are the plugs the right type? Some burn hotter than others.

-- Oren

..through the use of electrical or duct tape, achieve the configuration in the photo..

[MarkL]

If it's really related to whether the PTO is engaged or not, I would suspect a problem with the safety switch on the PTO, although it seems to be acting backwards from what I would expect. When the PTO is not engaged, the switch is intermittently causing the ignition circuit to be interrupted; when you engage the PTO, the switch is not a problem. Normally the switch fails the other way. Assuming the safety is part of the PTO switch itself, this would be easy to check. Pull the wires off the PTO switch and see if anything changes. You don't say whether the behavior coming off a hill is with the PTO engaged or not.

[Srgnt Billko]

I like that diagnosis. The only other thing that I can think of that would be related to PTO engagment is the governor. And I can't explain how to adjust it.

[brian]

I'll give that a try, i've also noticed that the AMP gauge has been acting crazy. It usually stays right above 0 but lately jumps to bout

17 then down below 0. Don't know if that would have anything to do with the PTO switch or not.

[Steve Barker]

Sounds like it running just a bit rich on the main jet adjustment. Try turning it down (in) a half turn.

[trainfan1]

I'd classify

"choke isn't opening fully so it's running partially choked"

more of a "carb problem" than a normal idle mixture adjustment, which is no problem at all, just a normal adjustment to be expected & performed occasionally.

Rob