Kelly 1,033 #1 Posted July 21, 2010 OK I put my onan back together got it started but it don't run right, I did a comp. test warm, 130PSI both cyl. I thought that was great, perfectly even but it does not run smooth, I swapped the carb, no better, changed plugs, then the wires, swapped plug wires at the coil, no better, pulled plug wires when running yup big change both sides, so I used a inferred temp gauge and I have 550+ deg on rear cyl. and 160deg on front at the exh. pipe about 2" from the block, so I know one cyl. is not running right and I checked another 520 that runs good and in 2 min. run time it read 580deg both cyl.'s so my front cyl. has got a prob. any idea's?? it has noisy valve train, I should adjust them, but I don't have gaskets and really don't want to pull the exh. and int. again for the 20th time I'm going to wear the bolts out pretty soon. Good comp. Good spark fuel seems ok could it be the valves??? not opening properly?? I know they are closing good or would not have good comp. Help, I love my Kohler's Share this post Link to post Share on other sites
rickv1957 75 #2 Posted July 21, 2010 Kelly, did you try another plug in front cylinder,Rick Share this post Link to post Share on other sites
fireman 1,022 #3 Posted July 22, 2010 Kelly, I seem to be having the exact same problem with my 20 Onan. The rear cylinder is running hotter than the front. Put in brand new plugs with no improvement. I tried searching online for an answer and couldn't find one. I'm gonna bring it to the local shop when I get a chance and have him check it out for me. If you figure it out in the mean time please let me know. Thanks Share this post Link to post Share on other sites
Kelly 1,033 #4 Posted July 22, 2010 Well I ate dinner and went back out thinking this has to be simple, it was, I had the intake on and off so many times it did not seal on the front cyl. so for now I put some silicone on it and it runs great, to check it I sprayed brake cleaner at the gasket mounting area and it killed the engine when I sprayed the front intake gasket, I'll order new gaskets and seal it up the right way, should be good. Share this post Link to post Share on other sites
Kelly 1,033 #5 Posted July 22, 2010 By the way after taking the plastis cap off the mixture screw and getting it to run better the exh. temp at the pipe about 2" from the block was around 580deg on both cyl.'s at idle, not sure what it should be but I'll take even anyday, well with in 10deg front to rear. Share this post Link to post Share on other sites
big mike 13 #6 Posted July 22, 2010 Well Kelly I'm glad you solved the issue. Any time I see a post about a poorly running Onan the first solution that comes to me is a long rope and a boat needing held in place. Share this post Link to post Share on other sites
Ken B 3,189 #7 Posted July 22, 2010 Nice too hear you got it running well Kelly, when the Onan is running nice they are nice. Mike: good one! :thumbs: Share this post Link to post Share on other sites
rickv1957 75 #8 Posted July 22, 2010 Kelly,glad to hear you got it going!,Rick Share this post Link to post Share on other sites