muuarren 0 #1 Posted May 4, 2013 Greetings all, I have recently been given a 520-HC in unknown condition. I was able to get it running, but at first it would only run with gas poured into the carb. After repairing a gas line I am now able to get it to start and run. At first it would only run on full choke with the throttle closed completely. Over time it began to run better and better, though still not awsome by any stretch. It will now run on higher throttle settings with the choke open... sometimes. I was able to mow a swath about twenty feet long (~60" deck), moving very slowly and stopping frequently so that the engine could recover. It would begin to run rough, like it was choking out. I would close the throttle and let it recover, then slowly throttle it back up. It would seem to be a carburator issue. Any insight would be greatly appreciated. I know that the Onans have their quirks or issues, but it sounds great when I can get it running smoothly. Thanks Matt Share this post Link to post Share on other sites
WH nut 553 #2 Posted May 4, 2013 Pull the carb a part and clean it would be the first step. Also make sure the fuel pump is good Share this post Link to post Share on other sites
bitten 133 #3 Posted May 4, 2013 Hello and welcome to Red Square. Lucky you to have that tractor given to you.Clean the carb and when you think you have it cleaned clean it again. Good Luck. Share this post Link to post Share on other sites
zeedubbya 18 #4 Posted May 4, 2013 Clean the carb twice as suggested above, adjust the valve lash, and then replace the spark plugs is my recommendation. If you have the time pull the heads, decarbon the heads, and inspect the condition of your valves, valve seats and top of pistons. As you may have read on here there are a ton of examples of valve seat problems on Onans. I hope it's just your carb! Good luck! 🀠And welcome to Red Square! Share this post Link to post Share on other sites
muuarren 0 #5 Posted May 4, 2013 Thank you all for your thoughts. Someone did mention the fuel pump to me... I fail to see evidence of a pump anywhere. I'll look again, as that is what it acts like. Any additional guidance would be appreciated. Share this post Link to post Share on other sites
muuarren 0 #6 Posted May 4, 2013 Okay, I see the pump. I was looking for an electric pump not a vacuum actuated one. It does spurt fuel out when I disconnect the line and crank it over. What I would appreciate, I guess is a carb cleaning tutorial. I am very mechanically inclined and capable, but carb stupid. Just never got acquainted the way I could have. too many diesels, perhaps. So if you could just point me in the right direction, I don't want to disassemble more than necessary. thanks again. Share this post Link to post Share on other sites
bitten 133 #7 Posted May 5, 2013 I have never did one on an Onan. The way I do the Kohlers is completely disassemble, clean, reassemble with new gaskets, adjust the needles to the Kohler manual install and do the final adjustment with the engine running. If you can get a Onen manual Im sure that it will have information in it. Good Luck Share this post Link to post Share on other sites
zeedubbya 18 #8 Posted May 5, 2013 Do a search for onan carb on here and you'll find all the answers you'll need. Some people only remove the top of the carb and some remove the whole thing. I've done both and it seems IMO that just removing the top and cleaning it real good works most of the time, but a thorough cleaning with full removal and gasket replacement is the best. Share this post Link to post Share on other sites
MalMac 1,328 #9 Posted May 6, 2013 Those carbs do not like even the tiniest speck of debris. You might consider installing a new gas line, filter and a good tank flush. After 3 total carb removal and cleaning on one of my 520's I determine that it was getting small bits of deteriorating rubber from the gas line. Not to mention the fresh gas was junk also with the ethanol in it. I did all the cleaning and replacing of line then some new high octane gas and that seem to work. Share this post Link to post Share on other sites
Rick Smith 0 #10 Posted May 11, 2013 Definetly clean the carb., they are prone to problems with dirt in the bowl of the carb. i have cleaned mine sevral times and after cleaning it runs great! Good luck! Share this post Link to post Share on other sites
muuarren 0 #11 Posted May 11, 2013 Thank you all for your help. I bought a new carb and it is now running. I picked the carb up online for $121 shipped. The local dealer wanted $170 for the rebuild kit. I'll think about rebuilding the old one along the way. I have started a new thread about my newest concerns. Thanks again for all the help on getting this far. Great community you have going here. Matt Share this post Link to post Share on other sites
cheesegrader 433 #12 Posted May 13, 2013 I don't know what kind of gold bars were included in your dealers carb rebuild kit, but I got what I think is the standard Onan carb rebuild kit mailed to my door from Sears for $44. Share this post Link to post Share on other sites
