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Old 10-18-2021, 10:21 PM   #1
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Knock-off carburetors for Onan Generators

I'm in need of a carb rebuild on my Onan Marquis 7000. I stopped by our local RV dealer's service department today and was told that they're no longer able to rebuild carbs and that a new Onan carb is $400+. The service manager there said that they haven't had good luck with the cheap knock-off carbs on Amazon and suggested I buy a kit and rebuild it myself. In looking for a kit I saw numerous knock-off carbs for sale for around $60.00-- little more than the price of a rebuild kit-- and the reviews on Amazon were amazingly good. Just wondering if there are users on here who have tried these knockoffs and what they thought of them? For $60 bucks it might be worth a try, but these days I'm growing more and more skeptical about the legitimacy of on-line reviews from places like Amazon.
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Old 10-18-2021, 10:44 PM   #2
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Quote:
Originally Posted by CamJam1 View Post
I'm in need of a carb rebuild on my Onan Marquis 7000. I stopped by our local RV dealer's service department today and was told that they're no longer able to rebuild carbs and that a new Onan carb is $400+. The service manager there said that they haven't had good luck with the cheap knock-off carbs on Amazon and suggested I buy a kit and rebuild it myself. In looking for a kit I saw numerous knock-off carbs for sale for around $60.00-- little more than the price of a rebuild kit-- and the reviews on Amazon were amazingly good. Just wondering if there are users on here who have tried these knockoffs and what they thought of them? For $60 bucks it might be worth a try, but these days I'm growing more and more skeptical about the legitimacy of on-line reviews from places like Amazon.
Are you sure you need a carb rebuild? My folks had a Pace Arrow with an Onan Marquis in it, and they were told they needed a carb rebuild. I searched around and talked to a few mechanics, and ended up buying some Onan 4C, which unfortunately is no longer available.

I opened up the carburetor bowl drain and filled it up with the 4C, then closed it. Came back the next day and drained it (it was very nasty and dirty) and did the same thing again. Then the next day I drained it and primed it, and it started up and ran like brand new.

If you do some searches there's other carburetor cleaners that might be similar, but it would be worth a try. I still have the almost full can of 4C, and I feel like it's gold
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Old 10-18-2021, 11:29 PM   #3
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Are you sure you need a carb rebuild? My folks had a Pace Arrow with an Onan Marquis in it, and they were told they needed a carb rebuild. I searched around and talked to a few mechanics, and ended up buying some Onan 4C, which unfortunately is no longer available.

I opened up the carburetor bowl drain and filled it up with the 4C, then closed it. Came back the next day and drained it (it was very nasty and dirty) and did the same thing again. Then the next day I drained it and primed it, and it started up and ran like brand new.

If you do some searches there's other carburetor cleaners that might be similar, but it would be worth a try. I still have the almost full can of 4C, and I feel like it's gold
Thanks for that advice. A good cleaning would probably do it, though you just never know and I thought rebuilding it would be the prudent thing to do. Anyone here know a good alternative to the Onan 4C that tap4154 refers to?
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Old 10-18-2021, 11:51 PM   #4
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Probably seafoam. The other thing to do is to install a fuel shut-off valve on the fuel line near the generator and use THAT to kill the generator when you want to shut down for storage - run it out of fuel in the bowl. The ethanol in the fuel absorbs water and then when it evaporates, it leaves chalky deposits in the carb which can only be mechanically removed - and frequently NOT removed. The carb also should be adjustable but new ones are neither designed for rebuilding OR adjustable, thanks to our "friends" at CARB in California, who think that if someone could adjust the carburetor, they might make their engine burn less fuel (or more fuel or just run properly) and that's taking the control away from They Who Know Better, who designed it to run like crap so you'd just throw it away and buy a new one.

Can you tell I've been dealing with this on a gasser RV for a bit?
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Old 10-19-2021, 12:27 AM   #5
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Quote:
Originally Posted by CamJam1 View Post
I'm in need of a carb rebuild on my Onan Marquis 7000. I stopped by our local RV dealer's service department today and was told that they're no longer able to rebuild carbs and that a new Onan carb is $400+. The service manager there said that they haven't had good luck with the cheap knock-off carbs on Amazon and suggested I buy a kit and rebuild it myself. In looking for a kit I saw numerous knock-off carbs for sale for around $60.00-- little more than the price of a rebuild kit-- and the reviews on Amazon were amazingly good. Just wondering if there are users on here who have tried these knockoffs and what they thought of them? For $60 bucks it might be worth a try, but these days I'm growing more and more skeptical about the legitimacy of on-line reviews from places like Amazon.

From my research on the Onan carb replacement , I've read where people are purchasing the aftermarket carbs and just using the fuel bowls .

It appears the bowl and jet get gummed up from the ethanol fuel which causes the problem . So rather than pull the entire carb off they simply install the fuel bowl from the aftermarket carb onto the original carb body .

The results have been successful , saved a bunch of money and much easier to do than to pull the entire carb off .

A couple years ago I had mine replaced with the Onan factory carb for $600 .

I'm going to purchase an aftermarket carb and keep it in my spares for future use if necessary.
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Old 10-19-2021, 12:53 AM   #6
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Find an old dental waterpick. Disassemble the bowl and float, and pull out the needle valve. Spray the entire assembly with Seafoam, let it sit a few hours, and then blast out all openings with the waterpick. All you get in a rebuild kit, really, are new o-rings and gaskets, and if you disassemble with care the old ones should be fine.

Eventually the needle valve and seat will corrode and then you'll need replacements, but most carbs can be cleaned this way over and over.
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Old 10-19-2021, 12:12 PM   #7
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I like the idea of putting the bowl from a knock-off onto the original carb! I'm first going to try cleaning the bowl and jet, but that will be my back-up plan. Thanks for the tip!
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Old 10-19-2021, 02:23 PM   #8
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The bowl is just that, a bowl.

It has no passages that can clog up or needle valve that can stick.

Take off the bowl and take some fine stranded electrical wire and stick it up thru the center passage a few times. That cleans out the crud so that the correct amount of gas is sucked up.
Wipe out the bowl and put it back on.
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Old 10-19-2021, 02:41 PM   #9
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Never replace Onan carb.. no no no.. unless badly damaged... they are made to be cleaned.. if you have a gas onan and you think carb is bad.. clean it.. so simple.. 90% of time you dont even have to remove carb..

Never replace.. clean.. then make small adjustments..

I clean on the eng.. pull off air cleaner.. use all safety precautions.. get spray carb cleaner 2 cans or so.. remove float bowl carefully.. and clean.. look into carb throat and spray cleaner in the tiny holes at top and bottom of throat.. the clean out bowl.. don't remove float.. count number of turns you make to turn out screw holding bowl to carb.. spray cleaner up inside main jet of carb.. that is where gas gets sucked up from bowl.. carefully spray float needle.. don't take apart.. take fuel line off.. and filter, if has one ... then spray though there..
Put bowl back on.. if you tare the gasket.. use RTV to seal carb bowl.. then start and adjust.. check output voltage..

There is a better even easier way to clean.. but I got to go.. maybe some else will tell us before I can get back with even simpler way.. also you tube KEVIN CAUDILL.. he shows piece by piece taking apart and cleaning
Good luck and let us know what you did and maybe better members then me will help you
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Old 10-19-2021, 03:13 PM   #10
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I worked on my Onan Marquis 5500 when it quit running. I could not even get a rebuild kit. Not sure exactly what model you have, but I ordered what was supposed to be an exact replacement for my carb, and it wasn't even close to fitting. Then I tore mine apart. The bowl was completely full of white pasty stuff. Cleaned it up. Spotless and all jets clean and free, float cleaned and free. Put it back on, would fire but not run. $360 for an OEM carb. Bolted it on. Started on the second crank and ran like new. I probably wasted 15 hours. Another time, I would just order the right carb from Onan and be done.

Sold that motorhome but talked to the guy that bought it and he has put over 500 hours on it. Still runs perfect.

Quick Edit: Did a search and the "Onan" carb kits and the China carbs are not even close to what my Marquis Gold 5500 had on it. I can tell just by looking none of the carbs listed would even bolt to the gen that I had.
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Old 10-19-2021, 04:23 PM   #11
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Quote:
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It has no passages that can clog up or needle valve that can stick.
An Onan carb has no float?
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Old 10-19-2021, 05:27 PM   #12
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I don't know about Onan, but I've been using those knock off carb's ffrom Amazon for my chainsaw, weedeater, etc, with great results. For $60.00 bucks I'd give it a try
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Old 10-19-2021, 06:35 PM   #13
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And I put a knockoff from Amazon on my house/construction generator (Briggs and Stratton engine) and it worked like a charm. Still does. Ran it on a job yesterday for over six hours. Starts on second pull.
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Old 10-19-2021, 07:02 PM   #14
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So.. back.. my super fast way to clean carb.. works 50% of time.. pull fuel hose and filter if has one on carb.. spray good carb cleaner in the fuel inlet.. reconnect.. remove air cleaner and housing.. use all safety precautions... spray cleaner in throat of carb.. main objective is those tiny holes in top of throat and the big one in bottom center..
Next.. find flat plate.. or scrap plastic.. to cover carb opening.. make sure what you use will not get sucked in.. no rags.. use stiff, hard plastic.. to big to get sucked in..
Start gen.. let warm up.. then cover throat of carb.. and choke eng down but don't stall..then repeat manually choking down.. about 3 times..
Then make small main jet adjustments until runs smooth.. check output voltage..
Make sure armature slip rings are nice and shiny..
Put back together and see if ok.. then add fuel injection cleaner to fuel.. error on the heavy side.. with fuel injection cleaner.. depending on how full tank is..
Then run gen enough to get injection cleaner in it..
This procedure pulls the trash plugging main jet up and out.. and that is the idea..
90% of time it's the main jet that gets vanished in it.. so if you can rush the cleaner you sprayed in bowl.. up through main jet by choking eng out.. most of the varnish gets pulled out and cleans main jet..
If carb is badly varnish.. removal and complete tear down to main jet cleaning

As always good luck and let us know what you did and maybe better members then me will help you
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