Kohler exercise causes engine spikes and gasping for fuel.

Replace battery with new proper sized.

Group 26R
12 Volt
525 CCA Minimum

Locked Rotor is reported as an overcrank fault "OC".

You first need to verify the engine fails to crank, which is likely a starter motor or start circuit failure.

If the engine cranks three separate times and then the OC fault occurs, it simply means the engine did not run... more likely a fuel issue.

But either can be caused by numerous reasons.

Ron, Try new plug/s first, sounds like the carburetor has dirt in it, you will probably have to remove carb. and clean/rebuild. From manual, other causes from your trouble shooting guide ,
? Faulty carburetor. ? Faulty cylinder head gasket. ? Faulty or misadjusted choke or throttle controls. ? Fuel pump malfunction-vacuum hose clogged or leaking. ? Intake system leak. ? Loose wires or connections that intermittently ground ignition kill circuit. ? Quality of fuel (dirt, water, stale, mixture). ? Restricted fuel tank cap vent. Check the attached links,instruction and guides, Good luck
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
http://www.kohlerengines.com/onlinecatalog/pdf/32_690_03_EN.pdf
Kohler KT735 3013 24 Hp Engine Parts
Kohler carb rebuild
How To Rebuild Kohler Series Carburetor K161 K181 K241 etc

Kohler Generator issue 20 RES - YouTube

? 0:24
www.youtube.com/watch?v=CT9u64dZna0
Apr 28, 2012 - Uploaded by Jeremy vanEyk
Brand new Kohler Generator Test cycle issue. ... Oh, and Mike, good call on the carb--that happens on some 20RES models. ...Indicates Locked Rotor (Lr). ... I'm on my second 20 RES-L,home depot swapped out the 1st one. ... Kohler 20KW RESA Whole House Standby Electrical Generator - Duration: ...

Disconnect generator remote start wires in the ATS. Put an ohm meter across the remote start terminals in the ATS and kill utility power, you should here a click in the ATS and the ohm meter should indicate close to zero ohms. If it does then your ATS is fine and the problem is gen control board or wiring between the two. If it does not show that value, then the start relay in the ATS is suspect.

The UV code has nothing to dow ith oil, poor oil would cause under frequency (low engine speed) Under voltage is caused by excessive load, short in the rotor/stator excition system, and/or AVR automatic voltage regulator. Of course loose wiring to will also cause it.

I finally solved the intermittant starting problem on my Kohler 12 RES by replacing the strater and the starter relay. I was also experiencing the occassional OC indication, red blinking LEDs on the ATS, and intermittent non-starts during the weekly exercises. The problem happened during power outages a couple times also. If I flipped the start switch between auto and run quickly the generator would occasionally start. Once started, the generator runs fine. I ordered a new starter, which included the starter solenoid. By the way, don't worry about the genuine part thing..the old starter was a Delco made overseas. I ordered a new starter online for $85 (6744N) and it was indentical to the genuine Kohler starter. Replaced the starter and it improved the problem but did not totally solve the intermittent starting. Ordered the starter relay (GM49746) replaced it and the problem is solved.

Can't search for a manual without model, type, serial, etc numbers...

A few things to take a look at:

1) Oil level / pressure sending unit. This is normally bypassed as long as the start switch is pressed. When engine starts, and switch is released, engine will die if sending unit is defective, or you are low on oil.

2) Exhaust temperature sensors. Older units were notorious for burning these up.

3) Cooling Water Temperature sensor. These cause trouble often, but mostly due to water pump impeller being eaten away by galvanic action and not able to pump water as effecively. End result is water temp higher than normal, which trips the switch, which kills the engine.

4) Alternator (generator) output not as it should. If output doesn't rise to proper level within a few seconds of engine start, the engine will be shut down.

5) Choke not working as it should

6) Bad fuel, bad fuel pump, clogged fuel filter.

http://www.homegeneratorsystems.com/service_support/manuals/index.cfm?rd=1

This link will take you to their site where you can download their manual.

Setting Exercise Timer
The Home Standby Generator is equipped with an exercise
timer that will start and exercise the system once every
seven days. During this exercise period, the unit runs for
approximately 20 minutes and then shuts down. Electrical
load transfer DOES NOT occur during the exercise cycle
(unless an utility power outage occurs).
A switch on the control panel is labeled “Set Exercise”
(depicted on page 10).The specific day and the specific time
of day this switch is pressed is programmed into the
control board memory.This date and time is then used to
automatically initiate the system exercise cycle.
To perform the Set Exercise procedure:
1. Choose the day and time you want your Home
Standby Generator to exercise.
2. On that day and time, set the AUTO/OFF/MANUAL
switch to OFF.
3. Press and hold down the “Set Exercise” switch for two
seconds.
4. Set the AUTO/OFF/MANUAL switch to AUTO.“Set
Exercise” is complete.
For example, if you press the “Set Exercise” switch on
Sunday morning at 10:00 AM, the unit will run an exercise
cycle the following Sunday at 10:00 AM (+/- 1/2 hour).
NOTE: “Set Exercise” will only work if the unit is in the
Automatic mode and this exact procedure is followed.The
exerciser does not need to be re-set if the 15 Amp fuse is
removed or changed.The exerciser will need to be re-set if
the 12 Volt DC battery is disconnected.
If you want to change the day and time the unit exercises,
simply perform the “Set Exercise” procedure at the exact
weekday and time you want it to take place.
• To prevent possible injury that might be caused by such sudden
starts, always set the AUTO/OFF/MANUAL switch to OFF.
• Remove the 15 Amp fuse before working on or around the
generator or transfer switch.

On your Automatic Transfer Switch ( the little gray box you see on the right in the picture above) you have two blue buttons. One is a Manual test switch. The other has a clock on it and this is your exercise set button. Hold it down for a FULL 3 seconds if you want it to excercise without a load (not powering your home) Hold it down for a FULL 6 seconds if you want it to exercise with a load every week. Your generator will start and run for 20 minutes, and then shut down. Now every week your generator will exercise at the time and day that you pushed the set button.