HorseFixer 2,012 #1 Posted October 7, 2011 When I got the 520H it ran like crap, Surging like a big dog the PO was a low buck guy and this tractor was on a path towards destruction, It had wrong plugs, Dirty Carb, Rock Hard Fuel Lines, Crud in Tank, Crap in filter, Black Gold Texas Tea Oil with fuel smell in it! So I corrected all of the above and she runs pretty darn good! It has a itty bitty surge at low Idle. I read in a post about a removable plug to get at the Idle mixture needle. In the picture below what is that Nylon Adjustment with the Left Arrow what does that do? Whats under the Right Arrow? And Finally whats under the Down Arrow? Looks like a BB in there. ~Duke Share this post Link to post Share on other sites
woodchuckfarmer 333 #2 Posted October 8, 2011 Nice tractor Duke, the down and left arrows point to factory plugs installed after machineing the passeges in the carb. The plastic thing is a limiter on the ajustment screw so we wont polute the world. remove it and ajust the carb. lots of them on cars of the 70s. ...I hope you like your 520, I like mine, its the best riding , fasrest mowing Ive ever had...good luck Wayne Share this post Link to post Share on other sites
HorseFixer 2,012 #3 Posted October 8, 2011 Nice tractor Duke, the down and left arrows point to factory plugs installed after machineing the passeges in the carb. The plastic thing is a limiter on the ajustment screw so we wont polute the world. remove it and ajust the carb. lots of them on cars of the 70s. ...I hope you like your 520, I like mine, its the best riding , fasrest mowing Ive ever had...good luck Wayne Thanks Wayne, You say the Down Arrow and The Left Arrow are Are plugged after machineing passages The Top one (Down Arrow) looks like a BB is pressed in there The (Left Arrow) one I was reading somewhere that you remove that plug, and there is an Idle Adjustment. So the plastic one is basicly a mixture rich lean adjustment is that cocrrect? can anyone shed some light on this? Thanks ~Duke Share this post Link to post Share on other sites
118lfd 8 #4 Posted October 8, 2011 It looks to me that the plastic cover is the idle mixture screw. They put the little tang on there to limit how rich or lean you can go. Pop the plastic off and the mixture screw is under there. Screw it in to seat it lightly and count the turns. Then back it out all the way and spray some carb cleaner in there, also clean the needle screw as well. A quick shot of commpressed air in the hole to blow out the passages and reinsert the needle. seat it and back it out the same number of turns as in the first step. Then adjust it slightly from there. Without the plastic cap you will have more adjustment. Share this post Link to post Share on other sites
HorseFixer 2,012 #5 Posted October 8, 2011 It looks to me that the plastic cover is the idle mixture screw. They put the little tang on there to limit how rich or lean you can go. Pop the plastic off and the mixture screw is under there. Screw it in to seat it lightly and count the turns. Then back it out all the way and spray some carb cleaner in there, also clean the needle screw as well. A quick shot of commpressed air in the hole to blow out the passages and reinsert the needle. seat it and back it out the same number of turns as in the first step. Then adjust it slightly from there. Without the plastic cap you will have more adjustment. Thanks, 118lfd I went out awhile ago and remoived the Cap as you and Wayne mentioned I had it down on Idle and adjusted a bit a felt a tiney difference But now I will fully remove and clean passage and needle as you suggested and reinstall and see whats up. :banghead: Share this post Link to post Share on other sites
htopjimmy26 3 #6 Posted October 11, 2011 Hey Duke, I'm pretty sure that the big plug to the right is the bowl plug and the main jet is behind it . Remove the plug and the bowl will drain and then you can see the main jet and remove it to clean if you want. I own 2 onans and my 416 surged so badly that it would barely run. I removed the plug and blew the jet out with carbclean and a little compressed air and shes as good as new..Good luck :thumbs2: Share this post Link to post Share on other sites
HorseFixer 2,012 #7 Posted October 14, 2011 Hey Duke, I'm pretty sure that the big plug to the right is the bowl plug and the main jet is behind it . Remove the plug and the bowl will drain and then you can see the main jet and remove it to clean if you want. I own 2 onans and my 416 surged so badly that it would barely run. I removed the plug and blew the jet out with carbclean and a little compressed air and shes as good as new..Good luck Cleaning that Idle Needle & Port Helped a Teeny Weenie bit, And from the Video I shown In the Resto Section she runs pretty good it's just Im trying ti get everything out of it I can, and there is still the smoke issue. Thanks HtopJimmy, When You say the Bowl do you mean this is the float bowl? If so whats up with that? Will it need to be replugged once cleaned & adjusted? If I'm putting a hole in the float bowl I don't want to take a chance & buck up my carb. Also If this the high speed Jet and its out of adjustment could this make engine run rich and cause smoke on acceleration? ~Duke Share this post Link to post Share on other sites
kpinnc 10,686 #8 Posted October 14, 2011 When You say the Bowl do you mean this is the float bowl? Yep. The bowl is the whole carb body. I love my Onans, but this was a bad design. All Nikki 6100 carbs are the same way. Just different size throats for different HP. Briggs used them for a while too, and most of the core parts are interchangeable. To be 100% sure Duke, I'd take the carb off and clean it properly. You can remove all the parts that a soaking would damage (gaskets, float & plunger, etc...) and re-use them. No need to remove the butterfly plates. They won't be harmed by soaking it. Check the float plunger tip for a "ring" where it seats in the inlet. It should not have one, and should still be soft and pliable. Remove the jet plug from the side (the metal plug), but not the jet itself (#6). There's also the idle jet inside on the top (#5). You can remove it with a screwdriver and clean it after you take the top of the carb off. It's not adjustable- so just seat it back in there when you've cleaned it. You may also want to replace the float while you're in there. They contribute quite a bit to the surging, and they don't shut the gas off the way they should because they get kinda "waterlogged". That will cause some blue smoke when you throttle up and rough running any other time. Share this post Link to post Share on other sites
HorseFixer 2,012 #9 Posted October 14, 2011 Thanks Kev Ill Hafta give that a Shot Later.. I better Get Buzy get that cab done and start my tear down, Do my leak dwn tests and inspect the cylinders and get chassis clean up painting done.. I will do what hya said on the carb when I start assembling everything. for your Help! ~Duke Share this post Link to post Share on other sites
woodchuckfarmer 333 #10 Posted October 15, 2011 Duke go into wheel horse links and check out the onan manual. its full of stuff on the onans....Have a nice time with your 520 ...Wayne Share this post Link to post Share on other sites
