RED-Z06 2,567 #1 Posted January 11, 2022 Not uncommon on high revving high overlap engines to get "standoff" where high velocity air/fuel slams into the back of the closing valve and reverberates back out...causing a cloud of fuel/vapor to hover just outside the carb or throttle body. On a 2 stroke you can get a bad reed letting air/fuel blow back thru vs sealing and get a spray out the carb. But my M12, prior to coming back apart was experiencing spitting out the carb. Now, i know and have verified my cam timing is correct, and that my valve lash is correct, that my valve was sealing...so what then caused this to happen? Ignition timing was still on also. The coil was pretty rusted, im replacing it ..they are spendy but im wondering if it wasn't effecting timing. Share this post Link to post Share on other sites
Maxwell-8 4,367 #2 Posted January 11, 2022 seems like a to rich running carb 1 Share this post Link to post Share on other sites
RED-Z06 2,567 #3 Posted January 11, 2022 7 minutes ago, Maxwell-8 said: seems like a to rich running carb And that's very possible, i did fight that carb for 3 days, like it wasnt atomizing fuel. But it'll all be new, carb, coil, pump, rod, piston, rings...God willing it will be a nice runner. 16 years in the weather wasnt kind Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,472 #4 Posted January 11, 2022 Have seen restricted exhaust do that. Share this post Link to post Share on other sites
RED-Z06 2,567 #5 Posted January 11, 2022 10 minutes ago, gwest_ca said: Have seen restricted exhaust do that. Yes thats definitely something that can cause it, when the Intake valve opens the exhaust pressure can spit back. This one did it with the muffler off. It also would on occasion spit fire out the carb on acceleration Share this post Link to post Share on other sites
Snoopy11 5,718 #6 Posted January 12, 2022 57 minutes ago, Maxwell-8 said: seems like a to rich running carb MONEY! I saw this thread in my email, and thought exactly the same thing. You beat me to it @Maxwell-8 Don Share this post Link to post Share on other sites
Snoopy11 5,718 #7 Posted January 12, 2022 @RED-Z06... were you seeing any fuel leaking out of the carb once you shut it off... Don Share this post Link to post Share on other sites
RED-Z06 2,567 #8 Posted January 12, 2022 22 minutes ago, Snoopy11 said: @RED-Z06... were you seeing any fuel leaking out of the carb once you shut it off... Don Not a drop, even held 20psi at the fitting from my mitivac. Share this post Link to post Share on other sites
RED-Z06 2,567 #9 Posted January 12, 2022 My question for the theory of running rich though, if i went any more lean on the high side it would hunt/surge, and any more lean on the low side it would backfire on deceleration. I do look forward to the new carb...if that fixes the running issue then im going to get really aggressive with the old #26 and peel it apart 1 Share this post Link to post Share on other sites
Snoopy11 5,718 #10 Posted January 12, 2022 9 minutes ago, RED-Z06 said: My question for the theory of running rich though, if i went any more lean on the high side it would hunt/surge, and any more lean on the low side it would backfire on deceleration. I do look forward to the new carb...if that fixes the running issue then im going to get really aggressive with the old #26 and peel it apart Yeah, could be float ithssue or cloggula in the carb... Worth buying new... Just make sure the valves are adjusted to spec. Only other thing I can tell you... along with verifying timing... (too far timing advance can cause such an issue... but I doubt it in your application). Don Share this post Link to post Share on other sites
RED-Z06 2,567 #11 Posted January 12, 2022 35 minutes ago, Snoopy11 said: Yeah, could be float ithssue or cloggula in the carb... Worth buying new... Just make sure the valves are adjusted to spec. Only other thing I can tell you... along with verifying timing... (too far timing advance can cause such an issue... but I doubt it in your application). Don I honestly thought maybe the timing was off this morning, kept shooting fire out the carb and muffler..then it caught and ran fine otherwise. When i got back inside i verified dot to dot on the timing marks...and when observing the piston and valves the intake valves just comes off its seat as the piston moves past tdc..so that's correct Share this post Link to post Share on other sites
Achto 29,388 #12 Posted January 12, 2022 38 minutes ago, Snoopy11 said: Yeah, could be float ithssue or cloggula in the carb... Worth buying new. Never met a Kohler carb that I couldn't rebuild to good as new. 2 Share this post Link to post Share on other sites
oliver2-44 10,703 #13 Posted January 12, 2022 16 hours ago, RED-Z06 said: But it'll all be new, carb, Don't throw away the old original carb. If you bought one of the aftermarket carbs, your got a 25% chance of it being any good. I've bought 3 and no more. Some get them and they work great, mine, one fuel ran out the inlet constantly. One idled well but never could adjust top end. One had poor idle and good top end. 1 Share this post Link to post Share on other sites
Snoopy11 5,718 #14 Posted January 12, 2022 16 hours ago, RED-Z06 said: I honestly thought maybe the timing was off this morning, kept shooting fire out the carb and muffler..then it caught and ran fine otherwise. When i got back inside i verified dot to dot on the timing marks...and when observing the piston and valves the intake valves just comes off its seat as the piston moves past tdc..so that's correct When I am speaking of timing, I am talking about flywheel. Make sure the timing advance is set properly... woodruff key... etc. I was thinking that it could be pre-ignition fueling... Don Share this post Link to post Share on other sites
