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Kohler 5RM62

Kevin K

Subscriber
A short time ago I picked up a Kohler 5RM62 from an ad on Craigslist. I was looking for an 1800RPM Kohler and this one came along. Kohler generators seem to be pretty rare locally. It has a twin cylinder air cooled K600 engine and will run on gasoline or vapor fuel. I believe it has been run on propane all it's life. The seller stated it had been sitting in his garage for the last twenty years as a "someday" project that never happened, and now he needed the room. It was presented as a "cold hunk of metal sitting on the floor" but it turned over by hand and had compression, so it followed me home. This sucker is HEAVY! It has to weigh well over 500 Lbs. If I had not handed the seller the cash before I loaded it, I may have backed out of the deal. Not a portable generator by any stretch of the imagination. Now that I have it I'm not sure what I'm going to do with it. Just a bit too heavy to easily move around.

Model 5RM62
Serial 211600 (made in 1957?)
Spec 4508A
Controller A-243675
Wiring Diagram 234676
5Kw, Single phase, 115/230 volts, 60Hz, 22 amps per term, 12 volt battery
Zenith carburetor with markings A270374 11653A
Pierce governor GC1448AR17
Wico Magneto XH2485 Specification XH-2485

No model or serial numbers were stamped on the engine data plate. I was surprised to find almost no parts availiblity for the engine. It seems Kohler has completely abandoned it.

The muffler was missing, along with the control box cover. Otherwise it seems complete.

After a good cleaning to remove years of grease and dirt, it looks quite presentable, not much in the way of rust. Somewhere along the way a previous owner repainted it a different shade of blue using a brush. The wiring in the control box was a mess with a few wires disconnected. I rewired most of it and replaced the selenium rectifier with a 50 amp 1,000 volt bridge rectifier. The choke was sticking closed, so I freed it up, disconnected the electric choke element (should not need it on propane), and adjusted the choke to be fully open at all times. There was no spark from the magneto so I removed it and cleaned the points which restored the spark. Due to the position of the magneto, to even clean the points requires removing it from the generator, unless you want to remove the intake and exhaust manifolds, which is more work than just removing the magneto. The valve tappet clearances were correct. The generator end seems to be in good shape with no discernable wear on the commutator or slip rings, and the brush length is very close to new. I would say this generator has very little run time.

Along with the generator came a literature package consisting of a wiring diagram and TP-1021 parts list for Spec series 45 generators. A K662 engine service manual and parts list is available on the web, along with a service manual for the Wico XH series magneto. Other than that, there is virtually no information available for this generator. Even here on the Stak there are only a few threads. Most of the hits I found were pictures of three of these generators auctioned off by the State of Oregon in 2015. I wonder how many of these were made? It can't be a lot. If anyone has a user manual I would appreciate a copy.

It came with Champion J12Y spark Plugs, which seem to me to be a higher temperature range than it should have. The spark plug insulators were white. The engine manual suggests J8 spark plugs, which I would expect. Does anyone know what spark plug should be used? The compression before I ran the engine was 125/130 PSI.

The generator end is massive for a 5Kw unit, far larger than the 5Kw Onans I have. I found a Kohler Field Data for AC generators table that shows the 5Kw and 6.5Kw single phase rotating armature generators to have the same shunt and field resistances, as well as the same exciter and aux field voltages. Is it possible Kohler just put a 6.5Kw generator head on some 5kw machines?

I ran the engine for 1/2 hour with no load then shut it down and changed the oil. The output voltage was normal at 115 volts. It seems to run well. The next step is to run it with a full load to see how well it does.
 

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Vanman

Subscriber
Sweet! If it is too heavy to move around, you just need to put larger wheels on it. :D

These nice old Kohlers are well built. I have my L600 down to just a bare block. It doesn't look all that big, but it is still difficult for me to move it around! :crazy:

What is the length of your generator field frame? We can compare it to my 6-1/2.

We could also do some armature part number sleuthing to see if it really is a 6-1/2 kW armature. Mine will be different regardless, as it is 120 volt, two wire only.
 

Kevin K

Subscriber
What is the length of your generator field frame? We can compare it to my 6-1/2.
The generator field frame length is 9-3/4". The part number is A-242240
The generator field frame circumference is 39-3/4"

The armature part number is B-242239
The field coils part number is A-242027

The way the parts book is set up makes it almost impossible to trace parts to another generator.

My generator armature is wound for 115/230 volts, so it would definitely be different than yours.

These old generators are really built well, and my unit does not appear to have a lot of use. Assuming no major catastrophe, it should be good for thousands of hours.

One thing I am surprised at is the engine breather assembly vents to the atmosphere instead of venting to the carburetor input to burn any oil fumes. I guess this is an old engine design.
 

jack0

Member
The field frame lengths are the same for the 5-6.5 units.
I can visibly see no difference.
I can't verify with measurements but the armature and pole shoes look identical between the two.
Must have been some internal differences.
I've often wondered about this and am glad you brought it up.

Jacko
 

Newoldstock

New member
8 sounds like a decent place to start with the plugs.
12 is hotter by quite a bit.

I don't know the engine and I am guessing based on other flat heads.
CJ8 sounds better and NKG BM6ES ( also a wild guess but in a close heat range )
Don't guess bad idea.
Now I am curious and will start looking at plugs for that engine.

Easy way to tell is look at the shell of the plug after a run and the insulator.
The shell should get hot enough to discolour a little.
The ground strap should be clean and show a heat line around the area of the bend in the hook ( this is also an indication of timing when everything else is right ).
The electrode should be clean have a light tan deposit.

Champion quality is not what it used to be.
I use NGK.
There are NGK fakes out there that run like SHITE from China ( buy quality from a good seller )

No model or serial numbers were stamped on the engine data plate. I was surprised to find almost no parts availiblity for the engine. It seems Kohler has completely abandoned it.
You are probably right.
Kohler Canada could not offer me any help with mine and had no information on it.
They put me in touch with a retired employee in the USA.
I can look for his email and phone number and PM it too you if you are stuck.

One thing I am surprised at is the engine breather assembly vents to the atmosphere instead of venting to the carburetor input to burn any oil fumes. I guess this is an old engine design.
Some companies did vent to the air cleaner as early as the 70s.
Briggs did it because I think they thought it was a wise business move to not piss off the EPA.
Tecumseh did not do this until later probably because they were already hard enough to tune without the added trouble of blow by gasses in the mix HA HA...

I think its better to burn them off if you can just for the lubricity of the oil getting sucked in combined with less risk of spitting up oil on things.

Quick search of Kohler turns up the M18 tractor/Utility engine that might be the same engine family as yours.

Its using a plug I am not familiar with rv15yc champion.

Best to break down the codes on your plugs and compare them with other engines in the same family ( checking head part numbers, and blocks ) and see if there is a patter to indicate what it might call for.

15 is a real hot plug.
Not sure why it would need to be that hot without some specific information on the plug, the M18 your engine and all kinds of stuff.

I also have to work in the morning so I think I will call it a night.
 

Vanman

Subscriber
My spec number is 5017B. For Group 201 (generator) that makes mine variation number 2.

Interesting. My field frame measures the same, but is B-242240. Perhaps a difference as subtle as how the controller mounts, or provisions for where the wires pass through... :shrug:

My field coils are the same, and it appears that our pole shoes are the same too.

The spec number system indeed does make it practically impossible to cross reference parts.

We need to find someone with a 6.5xx6x :D And see if their group 201 variation number is the same as yours. :brows:

Mine has a tube connecting the valve cover to the air cleaner, and the oil fill cap is a breather as well. I suppose if the blowby is a small enough amount, it might all go in through the little tube.

Keith

The generator field frame length is 9-3/4". The part number is A-242240
The generator field frame circumference is 39-3/4"

The armature part number is B-242239
The field coils part number is A-242027

The way the parts book is set up makes it almost impossible to trace parts to another generator.

My generator armature is wound for 115/230 volts, so it would definitely be different than yours.

These old generators are really built well, and my unit does not appear to have a lot of use. Assuming no major catastrophe, it should be good for thousands of hours.

One thing I am surprised at is the engine breather assembly vents to the atmosphere instead of venting to the carburetor input to burn any oil fumes. I guess this is an old engine design.
 

Vanman

Subscriber
We got lucky and found a 1965, 6-1/2 kW, 120/240, single phase set, including spec number, sort of. Looks like 5010D. I don't know what the other numbers that follow indicate though... :shrug:

Seen here at around 1:37:
https://www.youtube.com/watch?v=lEwZZ91VzJY

He's a member here, I'm fairly certain, but my memory is garbage, so I don't recall who it is. :(

If correct, it confirms my suspicion that this configuration was variation #1 in the group #201 generator section. So definitely different from yours. But, then again, yours is not 120/240, but rather 115/230, so.... :shrug:
 

Kevin K

Subscriber
That generator is a Spec 50xx, mine is a spec 45xx.

I wish I had more information on how the spec numbers work. About all I know is the first two digits of the spec number indicate a generator size range and engine model. The next two or three digits are for various changes in the build, sort of like the spec letter at the end of an Onan model number.

From the first few pages of my parts manual it appears as though the Spec 45xx series generators used the K660 engine. Maybe the Spec 50xx generators used the L600 engine?
 

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Vanman

Subscriber
Ah, you were ahead of me! I believe you are indeed correct about the first two digits in the spec number. The parts manual I have covers models 2, 2.5, 3.5, 4, 5, 5.5, 6.5, driven by the L600 engine, and says specification number series 0, 50.
 

jack0

Member
Looking forward to your load test.

I dug up some loads to put on my 1951 5r61-L600.
You might find the results interesting.
This is the first time I ran it past its rating.

Amp loads on grid power
2 toasters -14a
1 halogen light 3.75a
1 toaster oven 8a
1 heat gun 10a
Read with a fairly new amprobe meter.

Generator no load voltage 121, freq. 63.
Full load readings.
32 amps at 108.6 volts, freq. +58 with plenty of throttle left.
All loads on 1 leg.

This unit is on par with my 6.5r61 L654.

I wish I had enough 240v resistive loads to do a complete test, but none the less the results are fairly positive.

Still would be nice to verify 100% with part numbers.

I would think that as long as the k660 has enough ponies. Your results will be similar.

Jacko
 

Kevin K

Subscriber
Today was load test day for the generator, as well as giving me the opportunity to check on a couple of other things.

I replaced the Champion RJ12C spark plugs in the engine with the cooler J8c plugs recommended in the service manual. They worked well. I'm not sure why the hotter plugs were installed.

The magneto is set up to fire a couple of degrees AFTER TDC when hand cranking to prevent kickback, and should advance the timing to 20 degrees BTDC with the engine up to speed. I used a timing light to verify the correct operation.

Unfortunately I do not have any large propane containers, so I used a full 20 pound cylinder. A Camco TS201 regulator rated at 165,000 BTU was used as the primary regulator, connected to the demand regulator with 10 feet of 3/8" fuel line. Not an ideal situation, but it's what I had. I let the engine warm up for several minutes. The no load voltage was 115VAC (on each leg) at 63Hz. Load was gradually applied until I had 5,000 watts total, divided equally across both legs. The generator ran fine for about 10 minutes, then started missing. The 20 Lb cylinder and regulator were cold, and the missing subsided when I moved the cylinder. I placed the propane cylinder in the warm engine cooling air, and it ran well for the remainder of the test. These small cylinders just can't provide the necessary propane flow at higher loads. At 5,000 watts, the voltage was 118VAC on both legs (the transformer regulation was working correctly) at 60Hz. It ran an hour under the 5,000 watt load with no further problems.

The auxiliary field voltage was about 3VDC at no load, and 29VDC at 5,000 watts load.

Some day I will repeat the test with a better propane source and load it up to 6500 watts and see what happens. The generator seems to be in good shape for something built in 1957.
 

Kevin K

Subscriber
I just found another one like mine for sale in the Boston area for $800. The interesting part is that the owner kept the bill of sale from 1961. This cost $958.00 in 1961, about $8,220.00 in 2019 dollars, plus $270 installation, for a total of $1228.00, about $10,538 in 2019 dollars. Quite a bit of money for a 5Kw generator.
 

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Vanman

Subscriber
A lot of money, yes, but, as they say, "You get what you pay for". :brows: One thing's for sure. They sure don't make them like that anymore. Also have to realize that most small modern ones are cheaper in part due to Communist Subsidized Slave Labor.
 

dkamp

eMail NOT Working
When it comes to bona-fide emergency backup power, there's a whole lot more to the situation than just the ability to 'pull a load'... and that's where all the money really goes.

Buy the good'ns... so they're around for another sixty years, okay? :D
 
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