First, I'd like to thank Jeff for this video. It's very detailed and extremely helpful. I followed all of Jeff's instructions, put the bottom half of the carb back on and still had the same problem. I went a step further and pulled the entire carb off and put it on my bench. From there, I went through the same steps in Jeff's video as well as using an air compressor to blow through all of the holes in the carb. It fixed my surging problem and all of the outlets check out at 120-122 VAC. Thanks again for the help Jeff!

Thanks for this video, very helpful. One thing I can add having just taken mine apart is that you actually can remove the altitude adjustment pin. The black knob is friction seated onto the pin. The head of the pin itself has teeth much like a gear that allows the black knob to turn the pin. I used a tiny screwdriver to very gently pry equally around the bottom edge of the knob and pop it off. Once the knob is off you can just unscrew the pin and access the seat for cleaning or soak the whole bowl. A word of advice if you do this method, grab a sharpie and put an arrow marking the zero altitude position of the pin then count how many turns it takes to get it off so you can seat it properly again. Also, there is a rubber seal on the altitude pin, so be careful not to damage it.

Your video was helpful regarding how to take it apart and put it back together. I actually bought a replacement carb on Ebay from a secondary supplier. These replacements are now very reasonably priced--less than $50. Although I got a complete carb, I changed out only the fuel bowl with the new needle valve. I also installed a fuel shutoff valve. It started right up and runs smoothly! Now, after trips, I will shut the fuel off and let the generator run out of fuel, so no fuel remains to evaporate and gum up the needle valve.

Thank you for this video!!! I just fixed my inlaw's motorhome Onan Microquiet using your method. One thing I would recommend is instead of cleaning with carb cleaner, I own a $30 ultra sonic cleaner (can be bought at amazon or harbor freight). I just took the bowl portion apart and dropped it in the cleaner for 30 min and it came out perfect. Dried it, installed and it worked flawlessly! Thanks again for saving them a ton of cash!

I’ve worked on and rebuilt more Hollys, Quadra jets and motorcycle carbs than I can remember but your video was a lifesaver on this Onan carb. It isn’t too hard to clean but just getting it apart and understanding how the main jet works is the hard part. Mine had the solenoid plunger firmly gunked in place. It’s running now thanks to your video. Thank you, well done.

A friend used your video to clear up his Onan carb problems and referred it to me as well. I followed your instructions and it worked for me. Now my generator is running and I can take a few more trips and dry camp without worrying about the remaining battery power. Thanks!

A really helpful video: All these Onan generators are extremely sensitive to gas turning to varnish, which causes the surge problem, among other things (including, not starting at all). This is the best explanation I have seen anywhere on the internets on how to fix the problem. Even if your generator is older, this still tells you the essence of what you need to know.

Thank you sir! My RV is a toy hauler with a fuel station Recently in Mexico I pumped all the fuel out of the tank into my tow vehicle for the drive home Later that month I tried to run a generator maintenance cycle and it was surging like you described I followed your directions word for word and it fixed it the first time I appreciate the easy to follow the instructions Thanks again!

Jeff, I watched your video this morning and decided to try your repair fix when I got home. It worked perfectly. I ran the generator for 2 hours tonight and it never missed a beat. The stuff that came out of the float bowl looked more like vegetable oil than gasoline. Thanks for the helpful video.

Thanks so much Jeff. I had a code 36 with start, but quit immediately, right before a big camping trip. Your instructions were clear, detailed and accurate. Looks like my solenoid was probably a little sticky, and also when I sprayed backwards through the metering needle hole I felt like I heard some blockage break loose. Put it back together and it ran perfectly. Great video. You saved the day!

Your video is a life saver. I tried the seafoam method and it helped some. But then the carb got completely clogged and wouldn't stay running at all. This method is quick, simple, and 100% effective. Gen runs perfect now. There was a ton of gunk in the bottom of the bowl.

Jeff, I just followed your instructions this morning and it worked perfectly. Thanks so much for posting this video. You saved me a bunch of money and time.

Great information. I just finished cleaning my carb by following your instructions. After alittle trial and error by load testing, the generator runs great. The one mistake I made after cleaning I tested the generator by putting it under load by turning on the AC. The generator ran great until I shut off the AC and then immediately tried turning it back on. At that point the generator started to bog down. My first thought was that I didn't get it cleaned enough. After researching further, I found out that I was actually "short cycling" the AC, and that will either pop the AC breaker or it can also cause the generator to bog down due to overload. I further read that if the AC is turned off manually, that you need to wait 3-4 minutes before turning it back on. I guess I learned something new today. If it helps anyone else, do not test your newly cleaned carb by cycling the AC on and off. You saved me from purchasing a new carburetor. Thanks aging for your post.

Thank you for giving me the instructions to fix my Onan 4000. Your video no doubt saved me lots of bucks! Keep up the good work and helping those of us that appreciate the knowledge to make repairs themselves!

This video was a lot of help for me. I was able to clean my carburetor and get my generator running. Thanks for making the video.

We tried a lot of things and then ran across this video, and all the comments. After working on this thing for over a month, runs like a charm. THANK YOU!

Thanks for the video it was very helpful. I had to take mine apart twice. When I first started to work on the unit it wouldn't stay running at all. After pulling the bowl the first time and putting it back together it would run but not smoothly. I had decided to roll the dice the first time and not remove the altitude needle because I was worried about setting it back in the correct position. Don't worry about doing that if you attempt this repair just run the screw in all the way before removal counting the turns. Mine was 1-1/2 and after researching it I think that's pretty common. I pulled it down removed the screw for the needle after popping the black cover off. I cleaned the needle and jet as well as the the entire carb again. Put it all back together and started it back up. After a split second of running rough (heart sank) it smoothed right out! I ran the unit for around 30 mins loading it as much as I could and it performed great. Thank you so much for this video it made this repair process so much better!!

Thanks Jeff! I just did mine based on your video. I also installed a manual fuel shut off valve for the long periods of non use. Happy to say it is running like a champ now.

Thanks!!! I followed your video instructions and now my 2003 Onan 4KW purrs like a kitten. No more surging!

Thanks for the video Jeff. I haven't touched a small motor since the 80's, so I'm starting from scratch... lol. My generator started surging last summer, and now this year it won't start at all. So going to try your fix, along with a full service of the motor and see how it goes. Thanks again - I may post my results and any lessons learned.

Mr. Berry, We followed your instructions and now have a Fine running Generator! Thanks for the help. Curt

This video will be a big help for me for a recently purchased Micro 4000 that had bad gas in it. thanks so much for the detailed info

Thank you for this video. I followed your steps and it works perfect now.

Thank you for this video. I was able to save myself a bit of cash by doing this myself. Also as someone in the comments mentioned you can easily pry the plastic altitude stop back, so that the needle comes out for easier cleaning.

Thank you for sharing this video. You saved me a few hundred dollars. I was just going to order a new carburetor but thought I would try your suggestion. My generator was running very rough and surging. If I put the air conditioner on, the generator would just die out. I cleaned out the carburetor like you showed. Now, the generator runs like new. This was a very easy and inexpensive fix. Thanks again. Greetings from Palmyra New Jersey.

Thanks for this video. I thought it was gonna be much more difficult, but it looks easy enough. Will be tackling this job this weekend. Thanks!

Excellent video, solved the surging issue. There was a little debris that came out of the altitude needle valve when I flushed it with carb cleaner. After reassembly, the engine ran like new. I added a step to make it a little easier. I had a difficult time reaching the hot wire to pull the connector apart. I simply cut the wire closer to the solenoid and added another set of male/female connectors. It will make it easier if I need to do this again.

After letting our RV sit for two years I learned a BIG LESSON that these RV Gen Sets need to be run every couple months and have the fuel treated. If they don’t run they need to be put onto storage properly. We decided to get our RV out this year and prepare for some trips later this year. I discovered the Gen-Set a 4000 just like the one you shown was not getting Fuel and would not start. After Goggling the subject I came across You Tube Videos of guys using SEA FOAM to WHALE SPERM to clean their carburetors as they were all VARNISHED UP. After trying all those fixes freeing my ass off in windy 40 deg weather for 3 days, I was fixing to throw in the towel and told the wife to sell the damn thing! Then I ran across your Video and gave your instructions a Try. My Float Bowl was cruddy sith some silt and was coated with a Green Film I took a vinyl brush and carburetor cleaner and went to work concentrating on the Elevation Jet. I used an Air Compressor with 125 PSI air nozzle with a needle Jet Tip so that I could blow through all the jet holes so that worked Great. I operated the solenoid and visually confirmed that (it was operating) Then I blew out that port with Carburetor cleaner in that port hole and watched the spray shoot out all the ports. I went through everything again just for sure. I then assembled everything and it runs even better than it ever has since I owned it. Ken I would like to thank you very much for your great HOW TO it saved me $300.00 on not having to buy a new Carburetor. Thanks Again Jeff!

Great video. I have the exact same model Onan. Your fix saved the day.

Thanks man. I could not have done it without you. runs great now.

I am sitting in the AC comfort of a 1995 Roadtrek 210 Popular. Before, the AC unit would stall out the Onan genny and basically be a PIA to keep running. Tempermental to say the least. Wife sez "I just want to flip the switch and have the AC work like it does when we are on shore power. I don't want to keep having to restart the generator" Did your method and this baby purrs like a kitten! The altitude jet seemed gunked up like it had a coating of old gas. Probably had not been cleaned in years. (We are the second owners) It's all good now. THANKS!

Thanks jeff berry, Mine actualy would not even start. I partialy used your advice. I drained bowl disconected fuel line then hooked up a 2 ft pc of gas hose and sprayed carb cleaner(with drain closed) then i diconected wire to solenoid and ran a jumper I could not hear a click but after soaking and repeatedly working the solenoid i could hear a click. I just kept working it draining , refiling using the jumper on and off it now runs! I was trying to avoid carb disassembly cuz parts are unavailable unless a new carb is purchased. Just my way of doing it with your help Thanks Again!

Hi Jeff. I tried as you suggested and I could not get the main jet clean. As you know, there is a black plastic altitude adjustment knob on the end of the jet needle. As it turns out, that plastic knob can be carefully pried off using a thin screwdriver blade or similar thing. The head of the needle is splined, so that the black knob can be pressed on in the exact position. Make a good visible scratch on the brass head of the needle and the plastic knob, so the knob can be returned to the exact spot when you press it back on.Once the knob is removed, you can back the needle screw out all the way and remove it. Count the number of turns very carefully, in 1/8 turn increments (or smaller). In my case, it was exactly 6 turns before the needle screw came out. There is a spring on the screw to keep it from turning on its own, and it is important not to loose that spring! In my case, the spring still had a little bit of tension on it when I reached 6 turns, so it is important to feel exactly when the screw runs out of threads and comes out. When you put it back, start it back in that exact position where it came out so that you know for sure you are counting the turns accurately. Once I got the needle screw out, I could see the black debris that was clogging the jet, and also there was a little bit of white corrosion on the screw tip itself. Fortunately the corrosion polished off without pitting the tip of the needle screw. I sprayed carb cleaner through the jet, and also used a long toothpick to clean down the needle hole. Some additional black crud came out on the toothpick that did not come out with carb cleaner alone. I was careful to make sure no wood particles were left behind. I put the screw back in the hole and turned it six turns in, then backed it out 1/8 turn (making it a little richer). I *sure* that* last step violates some kind of smog rule - - but even when my unit was new it ran so lean it was always wandering in the RPM. At that point, I pressed the black cap back on the screw. Once it was all back together and primed, the generator started immediately, and ran flawlessly, with stable RPM.

Jeff thanks for the detailed video. I recently purchased an RV that sat for 5yrs I suspected the Generator carburetor would be gummed up and needed replacement, cost $300. Instead I followed your instructions, purchased seafoam to clean needles generator fired right up. By the way Seafoam works really good removed all varnish instantly allowed parts to sit for 1/2 hour then re-installed.

As a last resort, I carefully pried the black plastic knob off, and was able to unscrew the needle and clean the passage in the float bowl. I left the knob off, and adjust the screw in until the engine runs rough, and then back out 1/2 turn or so. Just like you would on a car or motorcycle. Instantly ran perfect.

Great information.Mine does not surge however I have to manually close the choke briefly to get it to run. I wonder if this too is a result of varnishing and cleaning as you did would fix it?

Thank you very much for a excellent video. I followed this process step by step and got my generator running after it sat for nearly a year without use. Thanks again, you saved me a ton of money!

followed your video with no luck the first time, so took your last bit of advice and took off the float bowl once again, but this time I used my ultrasonic cleaner with chemical cleaner recommended for ultrasonic cleaning. After three cycles of running the ultrasonic machine I dried off and then used a high pressure air sprayer from my air compressor, spraying out all of the openings and then reinstalled the float bowl and SHAZAM generator runs smooth as silk with no more surging..

Thanks Jeff for showing the traditional way to clean the carburetor. Remove and clean rather than rely on hit and miss additives in an attempt to solve the issue

absolutely q fantastic video. I cannot thank you enough!!!!!!!!!

This was very helpful. thanks for posting

What a terrific informative video. Your video has probably saved thousand and thousands for all the folk who have taken the time to research you tube. Unfortunately, I’m not one it worked for. I’m fairly certain I f9lloed your instructions to the letter but after reassembly, I still have the surge. I checked all the outlets to make sure I wasn’t getting the proper voltage, I was, and the A/C ran like a top Even with the surging. Since I ran out of time at the RV Park, I had to leave and couldn’t do anything more. I ran the generator with A/c load for approximately an hour during the trip home. The surging seemed to slow down some, and at time stopped altogether very shortly, say a minute or two then started again. Afraid i would damage something, I turned off the gen and A/c and after arriving home it sat in my driveway for about five days. I started the gen with remote start and the surge was still present. I turned on the turned on a/c after after about five min hoping the load would stop the surge. It did not but I was presented with a new problem after a couple minutes...the A/C started surging so I immediately turned it off and stopped the gen. Started gen back up and it still surged. So I then ran out of time and had to return the RV to storage and that was two days ago. I’m elderly and just had extensive back surgery about a month go so I wasn’t in any condition to try the process over again. As you mentioned it took you two time. My question is I’ve read all the comments and the one thing I didn’t do was follow a couple of the suggestions that said the altitude adjustment pin could be removed by popping off the black retaining cap. Since this wasn’t in your original video do you think it would be worthwhile to disassemble once again and try cleaning with the altitude pin removed. Following all the cautions from the other comments? You seem to be the best expert I’ve found on you tube and I highly trust you opinion. I just don’t know what else I can try to stop the surging and now that-the A/C started surging as well I’m concerned I really screwed something else up. Any ideas would be of immense help!

Great video. Enjoyed the detail. Have the same generator on my class c.

I had surging problems I took apart the float bowl like yo did in the video. Once I opened it up you could clearly see what I'm assuming was little tiny flakes of varnish I used carb cleaner to clean it out put it back together and it runs better than it ever did.

Very informative. My Onan 4000 Micro Quiet does not have a drain screw on carburetor. Do you know what replaced 4-C cleaner?

Exactly what I needed. Awesome!

Great video. Step by step instructions. Thank You

I have had issues like yours for years. I have had a trailer shop work on it twice, had it vatted by mower shop, I have worked on it, bought a new carb the whole nine yards and no fix. We hardly use the generator but wanted the thing to work properly if I did need it. We are fixing to take it back to our deer lease, so I decided to search KZfaq and found your post. When I watched your video and you said the fuel flow went thru the elevation knob in the bowl and the bowl can't be vatted because the plastic knob I knew that was the problem. I followed your video and it started nright up and runs perfectly!!! What a stupid stupid design Onan!!!! Thanks for your video, your the man!!!!!!!

I replaced pump and filter and fuel line to under frame where I put a line shutoff going to tank. I connected shutoff to old fuel line to tank..gen started right up for 15 min and I shut it off. Next day it started right up but only ran for 5 min. Could the fuel line coming out of tank be the problem. My gas tank is full. I need help

We have a one year old Onan 2800 on our 1 year old Winnebago Travato. Our generator at 11 hours of use began surging and dying. All previous use was just exercising the unit. I did attempt to do a cleaning with Seafoam in the gasoline and a few sprays or carburetor cleaner into the intake. Actually it would idle when spraying then surge and die. That did not work so we took it to the Onan sevice center. I was reluctant to take the time to do that as we have been told that Onan usually denies the warranty coverage. So they did a check and the called and said it was the carburetor would be warrenty covered. What a relief I did a happy dance! Then an hour later they called back and said “sorry we found residue in the bowl and that Onan would not warranty the repair”. The price for removing the unit and replacing the carburetor was said to be $961. I asked for a better price and they did agree to $650. So looks like what I have been reading all over the internet is true, if you put gas in your generator and follow the suggestions for keeping it exercised there still will be no warranty coverage for your $3,500 generator.

Thanks! The carb on my 4000 KY was shellaced up from disuse and wouldn't start. I took the whole carb out and cleaned it with carb cleaner. When I put it back together the engine was flooding which is a new problem. I found a smaller aluminum flat washer on the work bench that I think I missed installing. I see it in your video towards the end lying on your bench. It maybe fits above the solenoid and brass jet assembly and helps seal the gas delivery to the venturi. Sure hope so ($$$)!

THIS is the best video I have seen yet. you can find carbs on amazon now for 60 bucks. I just bought one I think I will post a video of replacement.

Hello. Could you suggest or recommend to me a good carburetor and fuel pump for a Onan 4000 generator? Thank you. Tom

im haveing no luck geting mine to even try to fire up , even with starting fluid any idias? your help would greatly be appercated,

What can I do on my Onan 4000 K Micro (20 years old, 350 hrs. no issues) to prevent these issues....?

Thank you for the video. My generator surges when idealing. When I put a load on, it smooths out and runs fine. Any advice please?

Thanks allot, I just cleaned mine, and it worked.

Thank you very much. Generator is running perfect now

Any replacement for the copper washer? What size is it. Working on mine today and lost that washer. Any ideas? I'm ready to put everything back and see if it runs. I assume it's an important piece and I cant run it without.

The washer in the pic next to the bowl, does that get placed inside or outside the bowl on re assembaly?

Great Video Thanks!

I am looking for a bracket to secure my 4000 gas to my 2000 Chateau with a chev chassis. if I had the time I could build one . But due to back and neck surgury I am limited..

Hey Jeff mine has a new carb and it surges, could it be the choke adjustment?

Worked perfect. My bowl was all gunked up. I cleaned it all out and now it runs like a top.

Will this apply to the Onan Microlite 2800 as well? Mine is surging too

Installed a 1/4" barbed shutoff valve (and another inline filter) which I will shut during driving times, turned on when stopped for the night. Pulled the failed spring loaded part out of the system and which is a common issue. Now I'm just relying on the shutoff valve during transport. No more issues, hopefully.

Great video. Fixed my issues. Thanks 🥹

While the bowl is off you can make a short pigtail wire with the solderless terminations to extend the solenoid wire making it easier next time.

I know gas is expensive and I don't know where you live but always run 93 Octane and always use Marvel's Mystery Oil. Make sure your idle and mixture screws are adjusted properly according to the serial number of your engine. This is important! Onan modifies these Gen sets a lot. The last letter of the serial number differentiates the series. ie...a,b,c etc. David

by the way great vidio, two thums up to you great job ,

Great video, I did everything you mentioned now I have a a gas leak from the bottom of the bowl, and it wont start, ( just turning over but not firing) Please help if you can Thank You

Soak in vinegar for 20 minutes Sometime I don't even disassemble carburetors I just soaking for 20 minutes and they work great afterwards

I used your video to clean my Cummins/Onan carburetor. Your instructions were perfect. Got it running on the first try after reassembly. Thank you so much! Now, what about those Cummins/Onan people who engineered this crappy carburetor? I have a snowblower and a lawn mower neither of which has to be drained or needs fuel stabilizer to start up after many months of non-use! I’m going to install an inline fuel shutoff valve, and run it dry after each use. Maybe that will help to avoid future problems.

Same generator. Wouldn't start, and used your method. Will start, but surges. Does it need cleaning again or likely something else (like bad gas)? How did you know yours needed to be cleaned again?

Thank you for great video.

Worked great. Just had to clean it twice.

If you take a flat blade screw driver , carefully pry the black altitude knob off. Then you can remove the needle valve. Count the revolutions when removing.

Jeff. Great video. My 4000 starts for a few seconds then stops. My altitude gauge broke off and I made the mistake of turning the screw randomly trying to get it to stay running. Is there a guess as to how far counter clockwise to turn the screw from fully seated? Also since it starts momentarily it’s prob not a bad control board right? I’m not sure what’s going on. Had a mouse nest behind the carb but don’t think they ate through wires. There doesn’t appear to be many wires on the back of the gen. Thanks!

Hi Jeff I am about to give-up on this carburetor. I followed your instructions, replaced the float, needle and gaskets, cleaned the entire carburetor twice with spray carburetor cleaner. Engine start after a few attempts, black smoke from tail pipe then surge to normal RPM and dies. Seems to be too rich mixture....... ?

Excellent!

A perfect instruction with no fanfare!

Thanks for vedio, did same and found jet stuck in hole had to really clean her up and after I finally got altitude mixture screw set to running state and it took awhile but she finally ran smooth I knew I had it and popped the plastic turn marker in place now I know altmanator was dead on to my 500' altitude. Load hardly makes I studder

the only thing it will do , is back fire threw the carb ?

The black altitude adjustment lever can be persuaded off, with a baby flat head screw driver from behind black knob.

Thank you thank you thank you

This video reminded me of the old days cleaning out jets and orfaces in all my old 2 stroke motorcycles. For the generators around the house I've been running NON-ethanol fuels which drastically helps on the storage life, also fill my toy hauler with same. For the motor home, I had to clean the float bowel main. Good video, but maybe drink less coffee? Screen shaking- Lol... Thanks

Working on a 4000 what a headache. Did find the shutoff was bad. Easy to check, connect the red wire to pos post and black wire to neg post on a battery. You should see it snap back. Sometimes parts get worn and they don't fully open. Andrew Mason was correct gently pry off the knob and it backs out. It is also easy to lose the position like I did. Next time I would mark it and turn it in and count till it stops. After cleaning, screw it in till it stops then back it out to what ever count it took.

Hey I guess you need to watch for the bowl gasket leaking when you reinstall. Thank you Nice Video

The black altitude knob slides off to reveal the jet knob and spring. You have to pry on the very bottom, from side to side until it makes enough headway to pull off with your fingers.

Pop the plastic cover off the altitude adjusting screw, then you can remove the adjustment screw for cleaning. Make sure you document how many turns in closes the valve before you remove it for cleaning. I scribed a line on the head of the screw and counted the turns in till it seated. 1-1/2 turns. The solenoid isn't a jet. It just turns off the gas flow when you hit the kill button.

Hello, would this fix work for a generator that only runs with start button pressed?

Thanks mi onan 2800 had the same symptômes i clean the part as tout Said ans wow Works like a New York savez me a lot if Time 👍

I watched this very good video. Unfortunately to no avail. Something about that darn needle valve is super finicky. After several attempts I succumbed to ordering a new carburetor. To my surprise on eBay I found a non OEM carb for less than $40.00. I was pessimistic, but I installed it and she started right up and runs smoother than I ever remember.

Awesome. Fairly simple to just remove entire carburetor. Well maybe not for most. But good to know about bowl jet.

Stupid question, how do I disconnect power to the generator? How do I check to assure it's off and safe? I do have a aux battery switch, is turning this off enough? Thanks for the video

Am dizzy after watching. Good video even with shaky camera.

I use an ultrasonic cleaner to clean my carb parts. This type of cleaner uses water and a degreaser so it is safe for plastic parts.

0:40 man, what an edit

Anyone no why onan 5500 QG EVAP STARTS UP GOOD BUT JUST WONT MAKE POWER ?IT WORKED FINE THEN IT JUST STOPPED DEALERSHIP SAID LOST GROUND OR LOOSE WIRE AT JUNKION BOX I WENT AND CK EVERYTHING ALL SEEMS GOOD SO IM THINKING VOLTAGE REGULATOR WENT OUT ANY IDEA FORSURE TO CHECK OR FIX TO GET IT BACK UP MAKING POWER AGAIN?

Mine generator is doing the same thing I will clean and let you know if it works thanks for the information sir .