Kohler CH25S/model 68583 on Simplicity tractor - engine dies when hot and under load

[Daymakes]

I've got a Kohler twin 25 h.p. air-cooled gas motor on my Simplicity garden tractor. We recently replaced both spark modules as it was losing power and only attained 1500 rpm after about 10 minutes of operation. After repair, the motor runs great for 5 minutes and then (when thoroughly hot) the gauges zero out (volt meter and tach) and the engine dies. the gauges come right back up after the engine stops and it will restart without a problem and run for 5-10 seconds max and then repeat. It will stay like this while hot. After cool down, same sequence occurs. Starts great, runs great with great power, cuts flawlessly until hot - about 5 minutes.

I changed out the brake pedal interlock and the fuel pump was new last season.

I wonder if this engine has a high limit cut-out that could be failing? There is a module speed advance that mounts on the left side of the motor behind the valve cover (facing from the front)that I was thinking could be the culprit. Since the temperature seems to consistently play a role, I'm not thinking it is a conventional short.

Thanks in advance for your wisdom.

Daymakes in Maryland

 

[Fish]

Yes, your S.A.M. Speed Advance Module is likely your problem area, but not necessarily the problem itself. To run properly, it needs a certain level of voltage.

And your gauges indicate a voltage problem, so I would look at the whole electrical system. Usually the problem is bad or corroded connections, like a keyswitch,
etc.

If you have a electric PTO, look at it closely, you might adjust it's gap if possible, look for hot wires, etc..

 

[Daymakes]

Yes, your S.A.M. Speed Advance Module is likely your problem area, but not necessarily the problem itself. To run properly, it needs a certain level of voltage.

And your gauges indicate a voltage problem, so I would look at the whole electrical system. Usually the problem is bad or corroded connections, like a keyswitch,
etc.

If you have a electric PTO, look at it closely, you might adjust it's gap if possible, look for hot wires, etc..

Do you recommend changing the SAM or going to the check out first? The system seems to be charging well - Also, concerning the PTO, why would it cut out only when the unit is hot? If it was a loose wire, I would figure it would also happen cold, but it does not.

Thanks for your prompt reply.

Daymakes.

 

[Fish]

I would start at the charging system, as well as adjust the gap on the pto clutch, as that is a huge load on the charging system,
set the clearance to @ .012 or so.

To check the alt, disconnect the leads, and take an A.C. reading across the 2 wires coming out from under the flywheel, it should
read @ 28 volts ac.

 

[fergusonfun]

so did you ever find a fix?

 

[mechanic mark]

http://www.kohlerengines.com/onlinecatalog/pdf/SM CH18-CH25 CH620-CH750 -ENGLISH 6-6-14.pdf Not your engine but same principle page 18 troubleshooting.

Post Simplicity model number, 7 numbers. Also post all numbers from engine. Thanks

Kohler Engines Scroll down to hot - will not restart

 

[Fish]

Wow!!!! Have I been pissing you guys off for a year now?????? Dang, time flies when you are having fun!!!!!!