252H 6 #1 Posted September 14, 2014 (edited) My onan has always ran fine except 4 years ago the 20 hp onan blew its governor and governor had to be replaced. It always ran perfect but recently it will not run right unless the choke is half way up- this is a new issue and it idles rough. If i lower the throttle to idle it will die even with the choke 1/2 up and it only runs ok with the choke 1/2 up and at full throttle 3600 rpms. It seems to rev up and down like ( vroom vroom vroom ) until you adjust the choke and throttle just right. Please post anything that can help or what you think it is. I dont know anything about these P220's. Perhaps a seafoam treatment will help? Edited September 14, 2014 by 252H Share this post Link to post Share on other sites
boovuc 1,090 #2 Posted September 14, 2014 You can try the Seafoam treatment. It is probably some debris in the carb as I have had it happen to me exactly as you wrote it. Take the top off the carb and remove the float and clean the bowel out as best you can then spray out all the orifices with Seafoam. I have even left Seafoam in the carb for an overnight then blasted it again before putting everything back together. It will make a difference! 2 Share this post Link to post Share on other sites
Ed Kennell 35,141 #3 Posted September 14, 2014 Clean the carb....Clean the carb....Clean the carb Share this post Link to post Share on other sites
252H 6 #4 Posted September 14, 2014 Thanks for the replies. I'll try that this week and see what happens :) Share this post Link to post Share on other sites
Geno 1,928 #5 Posted September 14, 2014 The one I just bought did that. Cleaning the carb took care of it. 1 Share this post Link to post Share on other sites
Martin 2,130 #6 Posted September 14, 2014 like other have said, clean the carb........ make sure you get the small holes in the idle tube............ had the same issue with idle on one of mine..... Share this post Link to post Share on other sites
252H 6 #7 Posted September 14, 2014 Im afraid to touch it because i dont want to mess it up like i did with my motion control. I dont even know how to access the carb. I wish i knew more Share this post Link to post Share on other sites
Dhodge 528 #8 Posted September 15, 2014 Make sure the carburetor manifold gaskets are not leaking / sucking air. The description of it running with the choke half open sounds to me like it is lacking the gas it needs to run because it is sucking air under one of the intake manifolds. Probably the back one. To check this start the tractor and give it a shot of starting fluid on the manifolds one at a time. If it smooths out temporarily when you spray it, well then you have an easy 20 minute repair. 1 Share this post Link to post Share on other sites
cheesegrader 433 #9 Posted September 16, 2014 There are some videos on Youtube that show how to carry out some really useful repairs. Search for Onan P220 Carb. You don't have to take the carb all the way off to clean it. If you take off the air cleaner housing (5 small bolts, if I remember), you are most of the way there. Two screws hold the top half of the carb to the bottom half. Unscrew, and disconnect the choke linkage, and the top comes off. You can now get to the float, and clean out the bowl. Most of the small jet holes that clog can be soaked with carb cleaner and blown out with compressed air. Soak. Blast. Repeat. Wear goggles. Don't get carb cleaner in your eyes! This is easier than it sounds. The first time I did this, I didn't get the needle valve back in the slot on the float properly. So I got the chance to do it a second time right away! Break tractor. Screw up repair. Suffer and stew. Fix it right the 2nd time. The Cheesegrader cycle of learning! 2 Share this post Link to post Share on other sites