Loss of power when PTO is engaged. 18HP Twin

[rcahoy]

Anybody have any ideas of what might be causing the engine to lose power when the PTO is engaged? Last time mowing on a very hot day, the mower seemed to get hot and started chugging and spitting, so I just quit mowing. Has done that before but was fine after cooling down. This time after cooling down it is not correcting the problem.

 

[digger]

Sounds like it's time to check the air gap on the PTO.
Or make sure that the field coil on the PTO hasn't started come apart.

And or make sure the spindles are greased up good.

 

[jdiederichs]

Remove the belt to isolate the problem, if it is the clutch or the deck, first off. Don't know what engine you have, could be a V-twin running on one cylinder?

 

[jchamberlin]

Randy: I used to have that problem when my exhaust valves stuck open. I could tell something wasn't right because it spun too fast trying to start it --no compression. I was running an opposed twin cylinder motor. Low ash oil helped the situation.

Edit: When they stuck hard I had to use aerosol Sea Foam to free them.

 

[nbextermueller]

Is it charging the battery properly? My twins seems to start to spit and sputter when the charging system is poor, the reg/rectifier is not working, and it starts running on battery alone. When the battery can't keep up, the plugs can't fire well enough.

The PTO makes this problem worse cause it sucks so much energy to keep the PTO engaged. While the Mag is only usually runs the plugs, if the regulator or battery is shot, it will be trying to power the PTO as well.

 

[mgonitzke]

Assuming we are talking about a Magnum or Command 18 (or any other magneto ignition engine), the charging system and ignition systems are completely separate and independent. You could unhook the battery and the engine would continue running.

 

[nbextermueller]

Matt, i disagree that the 2 systems are entirely independent of each other. If that was the case, then the bad battery in my 782/Mag20 wouldn't have mattered. The battery wouldn't take a charge, so when it ran low, the Magneto would have a hard time producing enough energy to run the PTO and headlights.

While yes, I do agree that the engine run completely unplugged and sitting on the shop floor. The 3 wire harness steals power from the Mag to charge the battery and therefore run lights and PTO.

Unless your telling me and Mag engine has both a Magneto and a Stator. I'm fairly certain it does not.

 

[nbextermueller]

I just pulled the engine out of my 2072 and I sure don't recall ever unplugging a regulator/rectifier.

 

[sblunier]

A Mag 18/20 has both a magneto and a stator. They are completely separate systems, but both are located under the blower shroud. The magneto has 2 plug wires and a grounding kill wire coming from it....that's it. The stator has 2 wires that generate 28-29VAC to the regulator/rectifier that converts it to 14-14.5VDC to charge the battery. They do not share power. In fact, if you put 12VDC on the kill wire you ruin the magneto.

This is NOT true of a KT-17...they run battery ignition, just like the K-series singles.

 

[mgonitzke]

What Steve said...

 

[sblunier]

Nic,

Since the charge wire is all the comes back to the main harness, there are only 3 wires in the engine harness, all in the same plug on the left rear near the fuel pump (kill, charge, low oil pressure switch). When you unplugged the main harness, you unplugged the regulator wire and the mag kill wire.

The regulator sits recessed in the blower housing just below the intake manifold on the right side of the engine. The stator wires attach to it and the charge wire goes into the main engine harness.