"MarkL" wrote in message
ups.com...
On May 5, 1:32 pm, 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.

Thanks in Advance


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.


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.