cleat 4,984 #1 Posted August 23, 2018 Well, I got the dreaded surge about a month ago. Happened around 1/2 way through mowing my 2 acre lawn. Finished mowing with the choke partly on then pulled machine into shop and cleaned carb while it was still bolted onto intake (it looked very clean inside with nothing plugged that I could see). Well, a couple of weeks ago I was mowing the back part and it started again so I finished with the choke partly on. Another thing I should mention is that before the surging starts there is a noticable loss of power with the machine working the governor very hard for little to no reason. Well a couple of days ago I pulled the carb right off and disassembled it. Again, it looked very clean. Blew it out then I heard a noise. Welch plug blew out. I was holding the blow gun a ways away from the carb too so I don't believe that I should have blown it out Reassembled carb (after I finally found the welch plug on the shop floor) and sealed up welch plug. I just now came in after mowing the entire yard with absolutely no issues. Tractor seems to have more power than it ever has. Even used less gas, less than 1/2 tank to do 2 acres and it was thick heavy partly wet also. I believe that welch plug could have been sitting in there loose the whole time. Whatever the cause was, I am happy now. This was my 520HC. Cleat 4 3 Share this post Link to post Share on other sites
posifour11 723 #2 Posted August 23, 2018 Good deal! Share this post Link to post Share on other sites
FatJackDurham 318 #3 Posted August 23, 2018 Welch plug? I saw somewhere that the intake manifold develops cracks along the seam. Share this post Link to post Share on other sites
Pollack Pete 2,273 #4 Posted August 23, 2018 On the 4 or 5 Onan powered equipment that I have,I use nothing but ethanol free gas and I load it up with Sea-Foam.Mater of fact,I use ethanol free in all my small engines.Our friends,the government are supposed to be using 10% or less ethanol.A friend of mine who is a member of the New York State Gasoline Retailers Association tells me that our gas usually has 20 %ethanol.Imagine that...……..the government could be telling a little lie. 1 2 Share this post Link to post Share on other sites
WHX?? 46,808 #5 Posted August 23, 2018 interesting Cleat, since running the choke partly on one can assume it was running lean or air going by the loose plug? Where was the plug located? 1 Share this post Link to post Share on other sites
cleat 4,984 #6 Posted August 23, 2018 It is a small little plug located just above the idle jet. 1 Share this post Link to post Share on other sites
posifour11 723 #7 Posted August 23, 2018 41 minutes ago, cleat said: It is a small little plug located just above the idle jet. You may have saved my late father's ss/16. That makes total sense! Share this post Link to post Share on other sites
Cee245 754 #8 Posted August 23, 2018 @cleat, Can you show us pictures and how did you get the Welch plug to properly seal? I have a P216 and it's developed a surge that I haven't figured out yet. Thanks Cory 2 Share this post Link to post Share on other sites
lynnmor 6,796 #9 Posted August 23, 2018 A welch plug is a one time use part. Clean the bore where it goes, then apply a small amount of fuel resistant sealant to the edge of a new plug and place it in the bore. Now take a punch and hammer and gently tap on the dome of the plug till it tightens in the bore. It doesn't take much and you should still have some dome shape when done. Hopefully you can find new plugs at an auto parts store. Measure the bore, I believe it is 3/8". Onan doesn't include the welch plug in their kits, but some cheap Chinese kits have them. 1 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 10,503 #10 Posted August 24, 2018 If the plug is tight and you want to seal it on the outside clean well. Get some nail polish your wife no longer cares for and apply a couple of coats to the edge of the cup. If it has some color it helps to see if your application is complete. Seal-All is another product that will withstand gasoline but I would not want to use it if installing a new plug. Too much chance of using too much and causing internal problems. Garry Share this post Link to post Share on other sites