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Onan Microlite 4000-Issues-Where do I go Next?


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  #1  
Old 02-04-2011, 08:25 PM
Atvfreq32 Atvfreq32 is offline
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Default Onan Microlite 4000-Issues-Where do I go Next?

Onan Microlite 4000 (4kw)
Model: KY/FA/26100H
S/N H980778012

I picked up this generator because the guy wanted a new one, said it ran, but was sitting for approx. 6 months. The guy said he tryed to start it but couldn't. I figured, a simple carb clean, and I have a generator. Well, I "cleaned" the carb, every nook and cranny, but, just would not start. This unit does not have an oil level switch. I do have the technical manuals for this unit. I have lots of spark. I thought, maybe brushes. Nope, contact rings cleaned, and a 12V signal going to the shut off selenoid while cranking. I found out that the carb changes up. Read alot about problems with the carb, so I bought an updated nuber carb, all be it a used one, it was like brand new. Put it one, still does not start. I found the timing specs, and checked with a degree wheel, where the spark occurs according to the degrees of crankshaft rotation. Seems odd that the point of spark was AFTER TDC. So, out of desaration, I moved the flywheel the amount of degrees the specification said. Low and behold, it appemted to start, but only if a held down the start button. Seems almost like the timing was out, but the tech manula has a key for the crank shaft and the flywheel. So, I firgured that the book should be right. I moved the flywheel back in line with the keyway, installed a new key and try to start it. No luck. I have spent hours trying to firgure this problem out, and now I am at the point of 1) checking into an insane assylum 2)using the gen as a boat anchor 3) or throwing it in the dumpster and sleeping good at night. If ANY ONE OUT THERE CAN HELP ME, PLEASE send me any information you might have. I really would like to get this this either going, or as far away from me as possible. ANy other information you need, just ask. Thanks.
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Old 02-04-2011, 08:47 PM
pegasuspinto pegasuspinto is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

the KY was onan's bad idea, I don't like 'em much

remember, you need 3 things, spark, fuel, compression. if you have those, it runs, if not, it doesn't. just that simple. the reason it started and died is likely that it didn't make AC or the controls are bad. So look it over and see which of the basic 3 is wrong....and get it back to startin and diein

Robert
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Old 02-04-2011, 09:03 PM
Gunny Gunny is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Does it actually start but then die when you turn loose the starter switch?
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Old 02-04-2011, 11:10 PM
Atvfreq32 Atvfreq32 is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

right now, it just turns over, just the same as it did before. I know that it needs spark, air, and a source of heat, that is what is puzzling about it. My theory is, that the carb I bought, may be the problem. After doing more research, I have found that some people have purchased up to four, to finnally get the engine to run. I am going in the direction of pullling the head, inspecting the valves, seats, cylinder etc. for any defects. As far as compression, I can barely turn the engine over on the compression stroke, so I know it has the compression. There is tons of spark, tried three new plugs, same result. The only thing left is the fuel/air ratio.....thoughts?
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Old 02-05-2011, 12:51 AM
mrmegoo mrmegoo is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

One thing came to me when I read your post about moving the flywheel to get a different timing & it tried to start. The flywheel is timed to the shaft with a key. That shaft, which is the rotor shaft, also has a timing pin & slot where it mounts to the engine crankshaft. That pin may be missing or sheared & allowed the rotor shaft to get out of time. Big job to tear down just to check, but it's a possibility.
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Old 02-05-2011, 01:54 AM
DLeach DLeach is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

The Onan KY series at best are jokes. I have worked on several of them.
Out of 10 of them, the exciter rotor was open on 6 of them. Two had bad magnetos. Everyone else uses the magneto to direct fire the spark plug. On this model they use a booster coil after the magneto. As far as timing I get the piston to the top of the cylinder, then turn the flywheel by hand to see if there is spark at the right time. The timing is 25 degrees before top dead center and is non adjustable. As long as the key is in the flywheel timing should be right. One other thing: Try setting the gap on the plug at 25 thousandths instead of the 30 they recommend.

Dave
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Old 02-05-2011, 10:12 AM
hoppyhunts hoppyhunts is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Check your valve clearance settings too. I didn't see you mentioning that it had been done.
Intake leaks? I would not spray ether into the carb, but try it along intake gaskets. Does it try to fire with that?
Will it run with a little squirt of gas directly into the carb while turning over?
I would try these things before tearing it down, or discarding it.
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Old 02-05-2011, 03:48 PM
DLeach DLeach is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Just thought of one more thing to check. The cam for the valves is driven by a nylon gear off of the crank. An easy way to check the cam timing is to remove the spark plug and valve cover.
Put your finger over the spark plug hole. Turn the flywheel by hand and watch the valves. Both should be closed on a compression stroke and you will feel the pressure on your finger. If you feel no pressure while turning the flywheel around twice, or the valves don't move, more than likely the nylon gear is broke or the key in it is sheared. Then you tear it down to fix it.

Dave
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Old 02-06-2011, 03:15 PM
Atvfreq32 Atvfreq32 is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Sorry for not giving all the information... yes, I checked/adjusted the valve lash several times before I got it right. The tolerance is so small that I found it difficult to get the measurment EXACT. Took a couple of attempts, but got it perfect. I shine a light dirctly into the carb with the choke fully open, and crank the engine to confirm, that there is actually fuel entering the intake. And yes there is fuel entering the intake. One thing I totally forgot to mention, is the fact that the new, updated carb that I bought, had the plastic main jet adjustment knob missing. I wrote down what the old carb was set at (approx. 2 1/2 turns out) and copied that to the new carb, which was 1 1/2 turns out from bottem. I tryed at every 1/2 turn out from bottem, figuring I could find a "sweet spot" just like a snowmobile, but still did not work. I tryed adjusting the spark plug gap as well, still no luck. mrmegoo, I will look into the rotor and crank timing, as I did not think of that. DLeach, it seems that the valve timing is good. Thanks for the insite. I will look into it, just to make sure. Any other suggestions?
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Old 02-06-2011, 06:03 PM
DLeach DLeach is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Ok as i get it you have fuel, spark and compression. If all happens at the right time, that engine should start. One of the three is out of whack. The magneto on that engine is at 4 o'clock facing the flywheel, hence the 25 degrees before top dead center in that rotation is counterclockwise facing the flywheel. If you have spark the shutdown circuit is not the problem. Check at the exaust while turning it over with the spark plug in place. You should have positive pressure there as any gas powered engine is basically an air compressor with a spark plug and fuel to self sustain it. If the valve timing is off you won't have positive pressure anymore than with an actual air compressor. Maybe over simplified but is the basis of a gas powered engine. If you have checked all of this, try a little starting fluid, this will tell you if it's a fuel problem.

Dave
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Old 02-07-2011, 12:09 AM
Atvfreq32 Atvfreq32 is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

The reason I am asking these questions, although seems really simple, is the fact that I have heard so many other issues OTHER THEN the engine. I just thought that possibly, someone out there saw any issues with say, the voltage regulator or something. People who have a better knowledge of this generator would know what is a weak point, and what to look for. I thank you very much for your incite, and information. I will go right through this machine, and keep you posted as to what I find.
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Old 02-07-2011, 01:03 AM
MBB MBB is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Atvfreq32
One thing not mentioned is an exhaust obstruction. To much back pressure. Try removing the exhaust. Is your fuel good? Actual compression test.
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Old 02-08-2011, 11:22 PM
Atvfreq32 Atvfreq32 is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Took the generator out of it's shell. Removed the head, used a dial indicator to find tdc, and checked where the magnets pass the coil. It appears that the magnets pass the coil just as the picton begins to travel down, indicating to me that the timing is late. Will try and pull the rotor out tomorrow to recheck the rotor to engine alignment.
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Old 02-10-2011, 01:03 AM
Atvfreq32 Atvfreq32 is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Got to the point of removing the rotor, but looks like it needs a special puller. Does anyone know where I can find a dissassembly manual?
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Old 02-10-2011, 09:54 AM
mrmegoo mrmegoo is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

http://www.cumminsonan.com/www/pdf/manuals/981-0503.pdf

This link should get you the manual you need. Other manuals are listed at the top of the forum under manuals links.
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Old 02-11-2011, 01:06 AM
Atvfreq32 Atvfreq32 is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

I got the rotor out tonight. The rotor plates look like they are twisted. The laminate is not broken, and there has been no contact with the stator. The pin on the rotor is fine, and there is no visible signs of slippage. SO, my next question is....at what point does the spark occur on a magnito engine? over top of the magnets or just after? Reason being, as soon as the magnets on the flywheel just pass the pick up coil, the piston is past tdc, not before. If I were to imagine the tiny plates on the rotor in line, the magnets would by passing by the pick up coil before tdc. The rotor shaft does not appear to be two parts, and there is no signs of movement, no chafed wires. Anybody with thoughts??

The manual you refered me to is not for my spec gen, however, there is information in it that is not in my service manual, so thanks alot for the heads up.
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Old 02-11-2011, 10:39 AM
mrmegoo mrmegoo is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

In your original post you listed the gen set as a spec "H", the manual I refered to covers spec A-M. If there are some major differences in your gen set to the manual you may have one that has been put together with various parts from other units.

BTW, the lamination plates on the rotor are assembled at a slight twist. This is done to smooth out the frequency in the 3600 RPM units. The shaft is a one piece unit.
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Old 02-13-2011, 01:35 AM
DLeach DLeach is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

Have you actually pulled the flywheel off of the unit? The magneto is at the 4 o'clock position. Looking at the magneto you will see three iron bars that the magnets pass by.
When the magnets are directly over these bars the crank should be at 27 degrees btdc.
The spark occurs just after the magnets induce a voltage in the magneto as they pass over it which gives you spark at 25 degrees btdc.
One of the wires goes to ground at one of the mounting screws for the magneto and is usually black in color. One of the wires goes through a midpoint connector and out to the blue or some color booster coil and uses a push on connector. The other wire is connected directly to the magneto via push on connector and goes through the junction block ( wire j1-11) to the control board for the shutdown circuit. Make sure the black wire on the booster coil is also grounded. I test magnetos by using a horseshoe magnet and having the sparkplug wire connected to the plug with the shell laying up against the engine block. Pass the magnet over the magneto, if you get a spark at the plug, the mag is ok. This engine does turn ccw facing the flywheel. I believe you said earlier you were getting spark, but it sounds like it's out of time. If this engine ran with the parts that were already on it, it should run again.
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Old 02-13-2011, 03:14 PM
DLeach DLeach is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

One other thing to check. The rotor is attached to the tapered shaft on the motor. There is usually a key in this taper. The manual doesn't show one, but this could be where your timing issue is coming from. If the rotor slipped on this tapered shaft, the timing would be off in that the flywheel is also attached to the rotor. Just another area to check out.
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Old 02-13-2011, 04:56 PM
George Clark George Clark is offline
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Default Re: Onan Microlite 4000-Issues-Where do I go Next?

ok ignition has to be before tdc there is no engine out there that will run with ignition atdc,failing to stay running is loss of ignition power from the generator end,once the set has started the gen output must provide ignition power,was your key spun out,if so you need to take the engine down a bit and find out what else is wrong,good luck.
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