big a$$ Kohler genset - questions

Sat Jan 14, 2012 10:39 pm

Hey team - I'm normally in the cub forum, but I picked up a great big generator for cheap. Its 12hp so I was told & I got it running today like a top. Electric start only.

Anyway - I had it all warmed up & going & decided to plug in my battery charger & toss it on the battery. After about 3 or 4 minutes the charger started blowing huge clouds of smoke & I had to quick toss it into the snow.

Now - it was a $10 autozone special - but I'm concerned that I may need some sort of voltage regulator or something.

So - how to I tell if I need something there or not? I'm kind of afraid to plug in a freezer as they cost a lot more than the batt. charger.

Re: big a$$ Kohler genset - questions

Sat Jan 14, 2012 10:57 pm

I regulate the voltage on my 3 generator sets with a multimeter.

2 of the gen sets are 120 & 240 volts. I adjust the engine rpms to get 120 volts with the generator loaded. 3rd is strictly 120 volt. Same proceedure - set voltage under load at 120 V.

Guessing - something shorted or wrong with the gen set alternator or the wiring. Might be an easy repair - or not. If you get the set cheap - might be worth repairing.

Also, Harbor Freight has generator heads for sale.

Re: big a$$ Kohler genset - questions

Sat Jan 14, 2012 11:18 pm

Thanks for that - I'll play around with it tomorrow.

I dont know anything about these - but it seems the older they are the less they generate - I'm guessing with a 12hp engine this will produce 3kw - the ID plate is there but its really hard to read.

Plus someone decided to paint it blue - in any case - it fires up & runs great - I must need to figure out this over voltage thing.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 7:57 am

Were you charging the generator battery while the generator was running? Does it not have it's own charging system for the battery. If so, you were feeding output from the two charging systems into each other. If I have mis-read what you were doing disregard this post.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 8:48 am

You know Big Dog I was doing exactly that. I just assumed it wouldn't charge its own battery but I guess I need to test that with the multimeter as well.

Dare I hope it isn't messed up?

I need to make a hybrid cub one of these days!

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 9:21 am

Miss read the initial post, thinking the generator head was smoking.

12 hp engine should have an AC output in the 6 to 7 KW range - that is if the gen head is an alternator. If the gen head is the universal motor type, then the output may only be in the 4 KW range.

I would start the gen set up again. Multimeter, check the voltages at each outlet - to see if the voltage produced matches the type of outlet. You can also check the voltage across the battery terminals to see if the gen set's battery charging circuit is still working.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 9:30 am

My feeling is that the gen set charging system is hardier than the cheapie battery charger. Do as Eugene suggests and check the voltages. Particularly at the battery to see if the gen set is charging it.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 10:40 am

Tell us more about the generator and check the rating plates, many of that type were old military and were NOT 110/220 volt single phase, though many of them can be rewired to provide that

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 11:49 am

OK - guys here are some details.

Kohler brand
12hp

The plate says the following.

Model = 4CM21
Spec = 10293B
Serial # = 461272
KW = 4
KVA = 4
Hertz = 60
Volts = 120
RPM = 1800
AMP = 33.3
Battery = 12

I'll go out there in about an hour & fire it up & check everything with the multimeter.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 11:53 am

serial number dates to 1976

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 1:09 pm

ok - 13.2 volts at the battery with the machine turned off.
18.0 & 18.1 volts at the battery with it running - with no load.

There is 1 household outlet with 2 plugs.

both ran just under 200 volts with the machine running and no load. 198

I'll load up some pics in a few.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 1:35 pm

I guess the VR is shot - about $140

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 1:38 pm

midget-farmer wrote:I guess the VR is shot - about $140

May be. Keep in mind that a lot of the older generator sets weren't that good at regulating voltage if they were operating with an open circuit.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 1:50 pm

Put it under a light to medium load and see what the voltage is. I agree with Jim - open voltage on the older gen sets was not regulated very well.

Re: big a$$ Kohler genset - questions

Sun Jan 15, 2012 4:32 pm

I googled that model, and there were several comments about over voltage problems. here is a link to the manual for it.

http://www.scribd.com/doc/6747196/Kohle ... ice-Manual