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Onan Generators

Onan BGE, should I just put it on the railroad tracks?


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  #1  
Old 08-10-2017, 07:20:47 PM
TurboTaco TurboTaco is offline
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Default Onan BGE, should I just put it on the railroad tracks?

The genset in question is an Onan BGE Model number: 4BGEF026100G and SN: C900309125 (my number tag is kind of faded so thos are the numbers as best I can tell).

Before I get into my real question I just want to say this site has been immensely helpful in troubleshooting my genset. I've read a dozen or more other threads of users asking questions. I just want to let you all know how grateful I am for the know-how here.

Onto the matter at hand...
I picked up an 85 Winnebago a couple months ago and it came with this Emerald I genset. The previous owner said he messed with the unit some but ultimately never bothered with it. Me being the foolish hobbyist mechanic I am figured "sure I can fix it easy".

First thing of course, clean the carb. The butterfly was free but when I pulled the bowl off it was full of varnish. I didn't rebuild the carb just soaked it a little in some carb cleaner and blew all the passages out. It would run for a little bit and quit, and while it ran it was hunting.

A few hundred dollars later I have replaced the brushes, cleaned the slip rings, changed the ignition coil, installed a new fuel pump, and couple other minor items. It still hunts, and the output voltage swings wildly.

Everywhere I read hunting is caused by a dirty carb or a poorly adjusted governor, but it surges so bad I can't adjust the governor.

As a last ditch effort I bought a voltage regulator from flight systems, but in the included book it says to have the generator running properly before installing the VR so not to burn it out. So my question is:
Could a bad VR cause the set to hunt like it is? No matter how much I mess with the mixture screws it has no affect on how the engine is running. I don't want to put my new VR in and have it burn up, or am I barking up the wrong tree entirely with the VR? If you guys need any clarification I'll be happy to let you know. HELP ME
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Old 08-10-2017, 07:34:53 PM
Ben Cowan Ben Cowan is offline
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Default Re: Onan BGE, should I just put it on the railroad tracks?

experts on that unit will be along soon, Sounds to me like you still have some issues in the carb. maybe very small holes that need to be physically cleaned. Luck, Ben
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Old 08-10-2017, 07:45:02 PM
David C David C is offline
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Default Re: Onan BGE, should I just put it on the railroad tracks?

Sounds like a plugged up carb. Take an old propane torch and remove the burner tip and the orifice (some do not have one) from the pipe. Slip on a couple of feet of hose, remove the air cleaner and slowly induce a little propane into the carb. If it lines out, it pretty well confirms a plugged carb.

David C.
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Old 08-10-2017, 07:50:57 PM
Kevin K Kevin K is offline
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Default Re: Onan BGE, should I just put it on the railroad tracks?

You have a 4BGE spec G generator made in March of 1990. This set has a mechanical governor, so most likely your surging problem is caused by a clogged "idle" passage in the carburetor. Another possible cause is an air leak in the sealant between the two halves of the intake manifold. The voltage regulator has nothing to do with the surging problem.

Plug a 1,500 watt heater into the generator and see if the surging stops. This would confirm it is the idle passages that are plugged.

Go to the twinslan site and download the manuals for your generator: http://www.twinslan.net/~n0nas/manuals/onan/

965-0528 service
965-0231 parts
965-0128 operator
965-0628 install
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Old 08-10-2017, 07:57:55 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

I'm gonna agree that the carb needs a good cleaning. I had a miller welding machine acting the same way. I finally had to trace each carb fuel circuit with solvent to find one plugged up. I couldn't blow it out and had to resort to drilling it out with a torch tip cleaner. FINGERS only, twist the drill a turn or two and pull it out. if its black crud do it again if you see any aluminum stop and go the other direction. took several tries but I finally cleared a chunk of carbon out of the passage and ahe was back to running smooth again.
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Old 08-10-2017, 08:19:52 PM
len k len k is offline
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Default Re: Onan BGE, should I just put it on the railroad tracks?

Could be the gov, but I'ld reclean the carb first. Likely has the same basic carb as my similar 7NHM has. Mine was hunting WILDLY and bearly ran when I bought it.

There are 2 long jet tubes you need to clean , they each have 8 tiny cross holes that were heavily plugged on mine. The 2 long jet tubes are in the aluminum casting dip tube that dips into the bowl. One tube is hiding behind a screw in cap.

I usually take the main jets crew out of it's "nut" and clean the screw ( that asembly holds bowl on of carb . Lot of times the tip is loaded with crud so I steel wool it clean.

On mine the idle jet had an aluminum disk over it so I didn't bother with it. Apparently it was clean since it ran perfect without cleaning it. There are also 2 short AIR jet tubes on top of carb by the M & S screw caps.

I blew out all the passageways with compressed air, including the 3-4 holes of .010 inch dia.
I never bother buying any carb rebuild parts, runs fine.

Last edited by len k; 08-10-2017 at 08:38:19 PM.
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Old 08-10-2017, 08:35:06 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

Slip Knott, The 4BGE is a good set in my opinion. I am currently sitting in my 5th wheel that has a Spec "P" running propane. Mine was converted from new to propane.
I agree that the carburetor has some jetting plugged.
I would ask you to try something. One) Have you tried to adjust the MAIN jet on the bottom of the carburetor? (If it has an adjustable main jet) Opening it will enriches the mixture. Second) With the set running and surging, MANUALLY and SLOWLY CLOSE the choke a bit and see if the engine stabilizes speed. If it does then the problem is with the carburetor being plugged in usually the small IDLE passage.
If the carburetor seems gummed up from old dried up fuel residue then you need to completely disassemble the carburetor and buy a gallon of carburetor cleaner with a parts basket inside. Don't leave it soaking for several days as the solution can eat aluminum if left long enough. If the carburetor looks like it had some water or prolonged moisture in it and there is white residue then I suggest you buy a quart or two of household white VINEGAR. Vinegar has a 5% acidity and will dissolve calcium deposits left behind from water and the aluminum alloy reacting together. AGAIN, don't leave the carburetor soaking for more than 6-8 hours at a time.
Rinse it good and carefully blow out the passages with compressed air. Watch that you don't over pressure parts on the carburetor and blow out a "Blind" plug. Blind plugs are a plug that is "staked" back into a larger hole on carburetors where the manufacturer drills smaller air or fuel passages then blocks off the bigger hole. Unless your gaskets, needle and seat are completely shot or dried up, Try the cleaning and re-assembly FIRST to see if the carburetor is salvageable and will work. If it works, then put a new gasket kit and needle and seat in it.
I rebuilt a very plugged up carburetor on a 2.5LK that I recently revived after YEARS of sitting with old gas in it. My float bowl is a steel one. I fabricated a screw-sealed drain so I can drain the fuel bowl when I am not going to run it for an extended time. The LK can also be run out of fuel without hurting it as it has NO voltage regulator to damage. Unfortunately, this is not so with the 4BGE so I don't recommend shutting off the fuel and letting the engine run out of fuel.
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Old 08-10-2017, 08:44:49 PM
len k len k is offline
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Default Re: Onan BGE, should I just put it on the railroad tracks?

Blow the float needle valve passageway backways to normal gasoline flow. Otherwise compressed air can launch the float seat into the backyard. My air tank is 150 psi., but I've cleaned carb with 40 psi and it worked fine.

As long as carb insides are not white with corrosion I just use gasoline and a tooth brush to clean the carbs. Toss the parts in a coffee cup or peach can of gasoline and blow them dry with compressed air.
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Old 08-10-2017, 09:07:03 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

I appreciate the feedback. Like I've said, I've had the carb off numerous times. I have experience cleaning small engine carbs but maybe I'm missing a passage. Does anyone have a step by step guide or a better break down of all the passages?
Quote:
One) Have you tried to adjust the MAIN jet on the bottom of the carburetor?
No matter how much I turn either the main jet or the idle jet needle it continues to surge.

I will clean the carb once more this weekend. I've just about had it with this genset.
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Old 08-10-2017, 09:09:29 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

As already mentioned could be carburetor. Open your carburetor again. Look into the bottom of the float bowl. Any new crap there? If clean, then ensure it is getting enough fuel by ensuring the fuel filter is not clogged full of crap. The fuel filter is a screen element built into the bottom of the fuel pump.

As for the title of this thread - "Onan BGE, should I just put it on the railroad tracks?" do NOT put it on the railroad tracks. It will derail a speeding locomotive causing a massive pileup and most likely only scratch a tin or two on the Onan .


*** Forgot to mention - Since you already opened the carburetor, ensure the flow adjustment is within spec since it may have been disturbed when you cleaned it.


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Old 08-10-2017, 09:19:01 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

Quote:
As for the title of this thread - "Onan BGE, should I just put it on the railroad tracks?" do NOT put it on the railroad tracks. It will derail a speeding locomotive causing a massive pileup and most likely only scratch a tin or two on the Onan .
Lol, there is quite a bit of love for these Onans out there. Don't worry, the genset is safe.

Quote:
*** Forgot to mention - Since you already opened the carburetor, ensure the flow adjustment is within spec since it may have been disturbed when you cleaned it.
Do you mean the float height or main/idle jet adjustment?
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Old 08-10-2017, 09:37:26 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

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Originally Posted by TurboTaco View Post

Do you mean the float height or main/idle jet adjustment?
Yup, float, not flow...
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Old 08-10-2017, 10:45:07 PM
len k len k is offline
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Default Re: Onan BGE, should I just put it on the railroad tracks?

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Originally Posted by TurboTaco View Post

.....Onan BGE, should I just put it on the railroad tracks?.....

I will clean the carb once more this weekend. I've just about had it with this genset.
Could put it on a pallet on a railroad car with my address on it
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Old 08-10-2017, 11:04:26 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

The newer chemdip carb cleaner isn't the same as it used to be. I've used both and have been disappointed with the newer stuff. A bud of mine has a shop and he gets a safety kleen product that has a basket that agitates as it soaks. it works much better than the old soak baskets.

And 5 minute epoxy works good to seal up those peaky blown out welch plugs. don't ask
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Old 08-10-2017, 11:17:04 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

It also could be the governor. There is a sensitivity adjustment on them. Look in the manuals that Kevin posted.
When you said that the previous owner fiddled around with it, that kind of makes me leery that he might not know his Butt from a Hot Rock. People like that should keep their hands in their pockets when trying to work on something that they have absolutely NO Clue about. You'll get it right!
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Old 08-11-2017, 07:40:06 AM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

I believe Lenk was saying to use a piano wire in those passages I know there's one half way up the stem of the main jet that's hard to get too. I may have a parts machine if you need anymore parts.

---------- Post added at 06:40:06 AM ---------- Previous post was at 06:03:55 AM ----------

I have two parts machines but don't know the spec both tins are gone with the model number. Need a picture of the choke on the carb to tell. Is your choke working properly ?
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Old 08-11-2017, 08:14:35 AM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

I can't help much on Onan in it's self but I have used a hot plate I bought at a yardsale to literally boil a carburetor in a pot to help clean it. It make take drastic action like this to clean the carb well.

do it outside.
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Old 08-11-2017, 09:10:40 AM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

surging can be caused by the positions of the governor spring ends relative to the travel of the gov. arm.

"higher" at the "fixed" or speed adjustment end creates inverse feedback that dampens surging

too much makes the generator less responsive to load changes.
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Old 08-11-2017, 11:22:03 AM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

Quote:
Originally Posted by Kevin K View Post
...Another possible cause is an air leak in the sealant between the two halves of the intake manifold. The voltage regulator has nothing to do with the surging problem.

Plug a 1,500 watt heater into the generator and see if the surging stops. This would confirm it is the idle passages that are plugged.
I'd advise NOT ignoring Kevin's insight here. But I'd add that if the surging stops when the 1500W load is connected, that could also point to an air leak.
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Old 08-11-2017, 12:52:38 PM
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Default Re: Onan BGE, should I just put it on the railroad tracks?

I'ld do the simple stuff first, like recleaning the carb and testing with a 1500W load. Lot of people not familiar with carbs had to clean them a couple times till they got it right. Usually carbs are not heavily corroded. Tell us what your carb looks like inside, little dirty or white with water corrosion.

Surging can be the gov, but is usually the carb. I'ld reclean carb first and make sure you take out and clean the 2 long jet tubes in casting tube that dips into bowl. Besides you want carb operating right before you adjust gov.
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