Engine dies out when PTO engaged

[Shacker 4]

Had my SB 421 with 11 hp Briggs running for about 10 min, driving in gear or not, when I engage the pto to mow it cuts out and dies. It will spin slowly and I can see the blades starting to move but cuts off. Almost like the pto is grounding something and just dies. 

[gwest_ca-(File Mod) 11,483]

You tractor has magneto ignition but uses a battery style ignition switch rather than a magneto ignition switch.

The ignition switch powers a kill relay that controls the ignition. That part is likely OK.

When the pto is ON one half of the pto switch changes the ignition circuit to the seat switch. Operator falls out of seat engine quits. Seat switch or wiring between the seat switch and pto switch will be the problem.

These diagrams should help.

Garry

[Shacker 4]

Interesting because my seat is solid on the frame. I will have to check it tomorrow just to make sure. Unless previous owner switched the seat out.

[Ed Kennell 41,978]

 to the Shack.

 

Garry has you covered....PTO / seat safety circuit problem.      I am not familiar with the SB model, but some seats have the safety switch in the seat, so look for a wire.

[gwest_ca-(File Mod) 11,483]

I was wrong on the kill relay.

You should have a magneto ignition switch with no kill relay.

Still think the seat switch or wiring is the problem. When operator out of seat the seat switch grounds the ignition wire.

Working on getting the correct diagram posted.

 

After all that there is a kill relay in the parts lists for the SB-421 so I guess the wiring I posted does apply.

Let us know what you find.

 

Garry

[Shacker 4]

Garry,

You were spot on. The previous owner must have removed the switch. Looked under the seat and two wires were hanging there blowing in the wind. I stripped the wires and tied them together, PTO turned right on and got to mowing the lawn thanks to you.

Thanks for your excellent work,

Dylan