Jon925mn 39 #1 Posted August 26, 2021 Have a 520 with Onan that runs good but on flat ground it will start with a little puff of black smoke that quickly disappears. Park tractor slightly uphill and she will start with no smoke. Tractor has new carb and the valves were adjusted during install. Really no complaints on power or performance so should I be concerned with the startup puff? On side note it does seem to have a delay before the other cylinder kicks in say 5 seconds or so. Hours unknown as meter stopped working and reads 821. Thoughts? Share this post Link to post Share on other sites
8ntruck 6,373 #2 Posted August 26, 2021 The puff of black smoke suggests that it is running rich at start up. Choke issue? Idle too rich? Float level off? Just some ideas. 2 Share this post Link to post Share on other sites
stevasaurus 22,229 #3 Posted August 26, 2021 8ntruck is correct, but something is making me wondering why your 2nd cylinder isn't burning fuel right away...black smoke may be because of that. Share this post Link to post Share on other sites
Snoopy11 5,713 #4 Posted August 26, 2021 Maybe rings on the second cylinder. Have you checked compression? If rings are worn, oil could be on top of cylinder, takes a few moments for enough fuel to mix for fuel to ignite. Had this issue myself on a briggs, and that was my issue. Don Share this post Link to post Share on other sites
cleat 4,984 #5 Posted August 26, 2021 A couple of mine start like that especially if they have sat for a while and you crank it for a longer period with the choke on Once they start and burn off the extra fuel which normally only takes a couple of seconds they run well with no smoke. 1 Share this post Link to post Share on other sites
lynnmor 6,777 #6 Posted August 26, 2021 Oil would cause white smoke, black smoke is excess fuel. My guess is that the float needle isn't sealing completely or the float level is too high. Chinese carburetor I guess. Share this post Link to post Share on other sites
Jon925mn 39 #7 Posted August 29, 2021 Messed with settings and got some improvement but start puff still there. It obviously is running rich as it drinks fuel. The replacement carb probably the problem but the one gunked up was also a replacement. This engine sat for years and now has maybe run 2 hours since cleanup so the more it runs might help also. Who knows if engine has ever been decarboned. Thanks all. Share this post Link to post Share on other sites
Bill D 1,599 #8 Posted August 29, 2021 What do you have for cold/hot compression numbers on each cylinder? Just curious. Share this post Link to post Share on other sites
Jon925mn 39 #9 Posted August 31, 2021 On 8/29/2021 at 11:10 AM, Bill D said: What do you have for cold/hot compression numbers on each cylinder? Just curious. Unknown. Ordered a kit so I can get some information. Thanks. Share this post Link to post Share on other sites
