Kutty516H 0 #1 Posted January 9, 2018 Hello; I'm new to the Forum and this is my first post. I hope I'm doing it right, my apologies if I'm not. I have a Wheel Horse 516H with an ONAN Performer 16 Twin Cylinder, The problem I’m having is that it only seems to want to run with the choke almost completely on, if not the governor is pulsing and surging and making the engine run rough and spit and sputter. All of The things I have done so far do not seem to have helped at all, They Include: Disassembled, Inspected, and cleaned Carburetor Disassembled, Inspected, and cleaned Fuel Pump Adjusted Float according to Service manual, Adjusted govenor according to Service manual, Adjusted Intake and Exhaust valves according to Service manual Installed new Electronic Ignition Module, Ignition Rotor, and Condenser ( All new parts from ONAN) New Spark Plugs New Fuel Filter I’m still having the same problems with it not running smoothly without the choke being almost all the way on. It ran totally fine until just a couple months ago, Nothing has been altered or changed to cause this rough running problem. Does Anyone have any advice or suggestions as to what it could be or what else I could try??? Help Please!!!!! THANK YOU Dave (Kutty516H) Share this post Link to post Share on other sites
WHX?? 48,796 #2 Posted January 9, 2018 Dave Some fellas report having to clean the carbs a couple times. A new fuel filter I presume?...never mind just saw it.. Check/replace the fuel lines . Might want to check the intake manifold for leaks. Spray some wd-40 around the intake when running. If engine pitch changes you have a leak there. Lots of other threads on this common problem. Search on Onan surging. Almost always a fuel delivery problem. You could try a new fuel pump they are fairly cheap. I have the same problem on a 20 to get sorted out someday. 3 1 Share this post Link to post Share on other sites
520hC-120 136 #3 Posted January 9, 2018 (edited) I was gonna say to completely REBUILD the carb, beacause I had the same exact problem with my 520h with the Onan p220g and this fixed it 🔝 Hope it helps Edited January 9, 2018 by 520hC-120 2 Share this post Link to post Share on other sites
Ed Kennell 38,028 #4 Posted January 9, 2018 I cleaned the carb three times on my p-220 Onan before the surging stopped. Installing the fuel lines after cleaning can dislodge "new" dirt. to the Dave. 4 Share this post Link to post Share on other sites
lynnmor 7,302 #5 Posted January 9, 2018 I sound like a broken record, but always check compression first to see if you have a good engine. Make sure that the welch plug near the idle mixture screw is still intact. If it is still good, clean the carb, you may need to remove and replace the welch plug to clean it properly. The plug will be destroyed when removing it. Cheap kits are available online, but only use genuine Onan manifold gaskets. 3 Share this post Link to post Share on other sites
Jerry77 1,218 #6 Posted January 9, 2018 An electric fuel pump mounted below the level of the tank output solved the problem on my 516 1 1 Share this post Link to post Share on other sites
clueless 2,976 #7 Posted January 9, 2018 I have a kohler OHC twin that started hunting with out the choke on a little. I pulled the carb and cleaned it, still hunting, pulled it again cleaned and rebuilt it still no change. Found a NOS carb for a decent price, put in on, runs like new. 1 Share this post Link to post Share on other sites
Jerry77 1,218 #8 Posted January 9, 2018 I need to expand on my previous post......My 516 has an untold number of hours on it, and I expect from the oil consumption that it is high...Carb needs cleaning I am sure...was surging really bad when I got it...ran seafoam thru it, replaced the fuel lines and added the electric fuel pump....except for rough running just after starting it runs really well...I let it go at that because I only use it for rough work...not mowing..( couldn't afford the gas (lol) ), so I haven't done the carb..bottom line - surging is caused by fuel delivery in a lot of cases.... 2 Share this post Link to post Share on other sites
Kurt-NEPA 755 #9 Posted January 9, 2018 I'm another one that had to clean the carb 3 times on my 20HP Onan. The last time I soaked in a gallon can of carb cleaner for two days. That did the trick. That carb looked like new when it came out. I've also had surging problems that came from gummed up governor linkage. I took the entire governor apart, cleaned it up and put it back together. That worked too. I've also had problems with deteriorating fuel lines. Little pieces come off the line and plug the carb. New fuel lines worked, at least between the filter and the carb. I'm also a fan of electric fuel pumps. I put one both my 1988 and 1995 520H. Can't say it helped surging, but it sure did help starting. 1 Share this post Link to post Share on other sites
WHX?? 48,796 #10 Posted January 9, 2018 Not to steal your thread Dave but what is involved in taking the carb off? I have never had a reason to pull one but I got a feeling unless I sell all my Onans eventually I am going to have to. It appears the carb is bolted up thru the bottom of the manifold and the bolts are impossible to get off without the manifold coming off? I have gotten by with just cleaning the carb in place but gotta feeling those good times are gonna end some day. . Share this post Link to post Share on other sites
WVHillbilly520H 10,373 #11 Posted January 9, 2018 5 minutes ago, WHX14 said: Not to steal your thread Dave but what is involved in taking the carb off? I have never had a reason to pull one but I got a feeling unless I sell all my Onans eventually I am going to have to. It appears the carb is bolted up thru the bottom of the manifold and the bolts are impossible to get off without the manifold coming off? I have gotten by with just cleaning the carb in place but gotta feeling those good times are gonna end some day. . Yep you gotta pull the intake manifold, but if you're real creative with a wrench I suppose you could finagle the carb loose from the intake ,kinda like this guy ,Jeff. 1 2 Share this post Link to post Share on other sites
WHX?? 48,796 #12 Posted January 9, 2018 Couldn't get at them with a crowfoot wrench or something like that? Share this post Link to post Share on other sites
WVHillbilly520H 10,373 #13 Posted January 9, 2018 3 minutes ago, WHX14 said: Couldn't get at them with a crowfoot wrench or something like that? Maybe but I think the crowfoot isn't long enough from the square drive to nut flare, but a cheaper brand wrench ,a torch, a vise could get you close...maybe something like this... 1 Share this post Link to post Share on other sites
lynnmor 7,302 #14 Posted January 10, 2018 Since the valves need periodic adjustment, it would make sense to pull the manifold, adjust the valves and check the manifold for leaks. The OP said he did just that. In addition, this would be a good opportunity to take care of the exhaust rust. Share this post Link to post Share on other sites
ol550 830 #15 Posted January 10, 2018 When cleaning the carburetor was the idle jet #5 removed and cleaned? The hole in the bottom can be plugged up to the point that one would not think there is a opening there. Behind the welch plug are three holes that meter in fuel in stages as the throttle is opened. Any one plugged will lean the fuel mix and lead to surging. The main jet #6 is fixed so any of the idle circuit plugged will lean the mixture. Just my 2 2 Share this post Link to post Share on other sites
