Kohler 1A21 Mag Timing Marks

joebiodiesel

New member
I've got a Kohler Light Plant 1A21-39373. It came from a camp in Adirondack Park in NY. The owner gave it to me as long as I promised to get it running one day. That time has come.
It had a light seize on it, but it rolls over nicely now. It makes oil pressure puts oil out the tube to the head, but I had to spin it forever to get oil up there.
I cleaned the sludge from the base and got the mag to make spark but I want to check the timing before I try firing it up. It had a broken valve in it and it appears to have been apart and reassembled. My mag doesn't look like the ones in the manual and I can find no flywheel hole that is referenced in the manual.

Also, I've seen conflicting posts about whether you can crank the unit without having a load on the generator. What's the final verdict? If I don't connect it to 24V can I worry about fixing the generator portion later? I'd like to see if I can get the engine running smoothly before I tackle that portion.
Any advice appreciated.

Joe
 

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Vanman

Subscriber
That's a very nice gift! In my opinion, these are the best generator sets in this size range ever built, portability not withstanding. :D

That is an odd nameplate. Is it the only one? Is there evidence of a larger one having been mounted on the side of the radiator or below it, adjacent to the mag?

That serial number comes up as early 1940.

Don't forget to clean the sludge out of the rod dipper windage tray. Have to drop the oil base to get to it.

Your plant can be run without a battery, but you must first disconnect the mag shut down lead before attempting to start. You must have done this already if you are getting spark. The controller will otherwise have it grounded in the absence of a load on the line.

In all probability the generator will build up once you start it, and voltage will be present on the output terminals when you get it running.

I can't help off of memory with the timing, but I will look in the manual. BTW, PM me an email address and that manual can be yours as well. :wave:

Edit. The explanation in the manual for timing the engine is pretty basic. Put the engine at TDC #1, and set magneto to spark there. Advance until kickback is felt during cranking, then retard one or two teeth. Pretty low tech! So I think I'd time it to where it runs the best. Compression is only around 4 or 5 to 1.

Elsewhere in the manual it states 30* maximum advance.

Keith
 

joebiodiesel

New member
Thanks for all that great info, Keith!
That is quite a wide range of timing! I'll set it up mechanically like I have done in the past.
I appreciate the tip on the windage tray. I would have completely missed that.
It does have another tag on the side of the radiator. The same info is on it though.
I don't want to run it long without looking at the generator. I just want to make sure it runs smoothly, then I'll get after that end.
If It ends up working correctly then I'll take it apart, clean it all up and get it ready for service. I need a generator that can run the lights in my when the power goes out.
Joe
 

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joebiodiesel

New member
Well I had some good luck and some bad luck.
The Bad: The replacement head the generator came with doesn't quite work correctly. The installed height on the valves is almost .4" higher than the original head. See pic.
The Good: There's probably enough meat on top that I can just cut them down and be close enough.
Also Good: Even with the valve height way high the Generator runs and purrs like a kitten. Even holds governed speed.
The Bad: IT only hand cranks. No auto start. No charging. Not even a trace.
The Good: I took the Gen cover off and found most of the brush holders seized.
The Bad: I got them all freed up and it still doesn't charge. Also cleaned all the points of any relay I found, but it didn't help.

I searched a bit and didn't find a thread related to diagnosing the generator section. I'm a car guy, and I know it can be maddening trying to help someone diagnose a complex problem over the internet. Is there any way for me to help myself with this? I understand electrons pretty well, but can't seem to make sense of what's going on with this thing just by looking at it.
Any help or abuse welcome.
Joe
 

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Vanman

Subscriber
Hi Joe,

Wow, those valves are crazy. Would think that would wear out the valves and guides pretty quickly like that.

I just remembered about sending the manual, and sent it a few minutes ago to the email address you provided.

There is a very good description of the automatic switch, as well as schematics in the manual. It is really just the sum of several simple circuits. As long as you have a multimeter and some patience we can figure out what's wrong and hopefully get it fixed.

Keith
 

joebiodiesel

New member
Hi Keith. Thanks so much for that manual! It's very descriptive. I should be able to get it figured out using that.
Those valves are definitely too high. I can't leave it like that. This generator came with a bunch of parts. The head that was on it is in really had shape. It came with another head, so I cut the valves and seats and put it on. It's not right though. I also have a bunch of new valves that came with it. It's time to sort though the box and see what the best solution is. At least it's running though.
Thanks again!
Joe
 

joebiodiesel

New member
Tonight I started to diagnose the Generator End of my plant. Because of the mouse infestation it had I decided to take the brushes/holders and wiring apart for cleaning before driving myself too crazy, and in the process I broke an arm off the bottom brush holder. I can probably make something to hold tension on the brush, but if original parts are still available I'd rather go that route. Anyone know of a source for one?
Joe
 

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joebiodiesel

New member
VANMAN, that you for sending the manual to me. I love how it breaks the entire circuit into bite-sized chunks. It made the diagnosis easy.
My plant now autostarts, charges and runs like a champion. My next job it to fix my valve height problem, repair the broken brackets for the electrical box and then put it to work for a bit. Once I get bored of playing with it I will take it apart and give it the cleaning and paint job that it deserves.
This has been fun.

Thanks again,
Joe
 

Andrew Mackey

Moderator
Are the valve heights the same between the 'new' and old head? The valve train between the letter and 21 series engines was basicly the same. The difference was in the rockers and the pushrods. The valves were nearly identical. You need .008" on the intake and .010", engine cold on the exhausts for clearance. Each set of valves is set with the individual cylinders set at TDC Compression. You MUST use a cork gasket on the rocker cover, I think it is about 1/8" thick.. If you just silicone it to the head, it WILL hit the rockers! By just looking at your photo, it looks OK to me - that's the way they were built.

As for oil, SAE 30 NON Detergent is best over 40F. SAE 20 below that, NO multigrade, it is too thin for the plunger type pump. The reason for non-detergent: detergent oil makes any dirt in the oil to remain in suspension. This is so the oil filter can filter it out. As the kohler 4 cylinder engines do not have filters, you want the crud to settle to the bottom of the sump, where most of it will drain out during an oil change. Remember, you want to change the oil HOT so the sludge flows when the oil is dumped. Due to the nature of the oil pump, it will take quite a few turns to get oil to the top of the engine. usually, if the electric starter is used, or even if not, when the engine starts, you should see oil in the spyhole within about 30 to 40 seconds, no more, once the engine starts. If it takes longer than that, something is wrong - poor fitting plunger, crud in the relief valve, poor fit in the oil line swages to the top end.
 

joebiodiesel

New member
Thanks for the reply, Andy. The installed height is way different between the 2 heads. The original head is really rusty, and has 2 valves stuck in it really hard. I have new replacement valves for it, but I also got a complete head with it too. The new head looks identical but the valves have a thicker stem and the installed height of the valves in the new head is higher. When I put the new head on it the rockers were only touching a corner of the valve, so there was no way to correctly set the lash. Something was going to break with that kind of geometry. I ended up shimming the rocker bar to get it right. After measuring it, I wasn't going to be able to remove enough material from the top of the valve to get it right. It's OK now though.
Thanks for the tip on the oil. I found a previous post of yours that talked about that, so that's what's what I'm using. When I cleaned the sludge from the base, I added a couple of quarts with the cleanout door off (by leaning it back) and hand cranked it. It immediately started dripping oil from the crank. It had to spin it FOREVER to get oil up top though. I won't do that again!
Joe
 

joebiodiesel

New member
I've got a few more questions:

1)How do you set the governor speed on these? I was thinking of doing it by frequency. Just make it charge at 60Hz. It's a little high at the moment.

2)Should the engine RPMs drop significantly on high load? The reason I ask is that if I fire up my barn fan it takes a while to get spinning. I measure the charge voltage and it drops from 120VAC to around 100AC for around 15 seconds as the fan spools up. Once it's gets going the generator voltage returns to normal and the fan spins like it should. I've checked to see if it was a voltage drop in the wiring, but the voltage is the same all the way back to the brushes.
While I've never run one of these before, a modern generator engine would labor and lose RPMs when it started a heavy load, but this light plant doesn't seem to labor at all. I just loses charge voltage without any loading of the engine. Was this normal for them?
If this is normal then I worry I won't be able to start any kind of electric motor, like the compressor on the fridge or freezer. I'm sure it should be able to run more than stuff with a purely resistive load, but I doubt it could do it the way it is now.

As an interesting side note, if anyone ever breaks the tensioning arm off the brush holder, they can be readily repaired with that aluminum welding rod. Clean it up good with a wire brush and bring it to the melting point with a torch. That aluminum rod flowed right to it. Made for a great permanent repair.
Hopefully that helps someone else that might run into it.

Joe
 

Vanman

Subscriber
The speed is adjusted by adjusting the length of the rod between the governor arm and throttle. I like to set them to 60 cycles at around 1/2 ~ 2/3 load, with a resistive load.

Under the brush cover, up near the top, there is small relay. It’s coil is in series with the load, and it’s contacts shunt a portion of the field resistance. It is designed to pull in at around 1/2 load. At 1/2 load (resistive) this restores the voltage to that of no load.

Be sure that it pulls in above 1/2 load, that it’s contacts are clean and making good contact, and that the adjustment band on the field resistor is making good contact with the resistor itself.

Beyond that, the voltage will droop under heavy load, and particularly a reactive load, such as during motor starting.

I would imagine that a fridge or freezer won’t be any trouble, but larger motors will. Repulsion start motors are far and away the best type of motor to use with these as they’re starting current is less, and somewhat lower voltage while starting is better tolerated, depending on the type of driven load.

I have toyed with the idea of adding a second relay that would only operate above rated load to cut out the remaining field resistance, just to give the generator better motor starting capability.

Keith
 

joebiodiesel

New member
Thanks for that, Keith. that was exactly the problem. The relay pulled in but the points were not making good contact. After fixing that there is definitely a change in engine load when I plug the fan in. It spools faster now.
Interestingly, if I slow the engine down to get 60 Hz, my charge voltage drops to around 95 VAC. In order to get to 115 VAC I have to get to around 72 Hz. I'll have to fool with that next.
This sure has been a fun project so far. I love to hear this little plant run.
Thanks again for all the help!
Joe
 

Vanman

Subscriber
No problem, Joe! The overall low voltage sounds like the other adjustment band on the field resistor is not making contact.

Keith
 

joebiodiesel

New member
Got to fool with the Kohler again today. Got it charging 60Hz at half load and it only varies a few Hz from light to heavy load.
I'm impressed at how clean the voltage is coming out of it. My Generac sure doesn't look that nice!
Joe
 

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Vanman

Subscriber
“They don’t make ‘em like they used to” is definitely not just an idle statement. :brows: Glad to hear you’ve got it all dialed in and working properly. :salute:

Keith
 
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