Good_Ole_JR Posted May 25, 2000 Share Posted May 25, 2000 Both of my 3212's backfire when i throttle down. i just live with it. i have the carb set so that i have maximum power so that i can till, mow, plow or do anything else that requires the maximum horsepower needed to do the job. you might try just throttling down slow so that the raw gas wont ignite in the muffler. Link to comment Share on other sites More sharing options...
Les Posted May 25, 2000 Share Posted May 25, 2000 EMail: david.a.sohn@boeing.com To reduce backfiring symptoms, here are a few more ideas you might like to try... 1. Ensure the cooling fins are completely clear of debris and the engine is not overheating. 2. Clean out carbon buildup from combustion chamber. This should be performed about every 100 hours on most models. 3. Use high- octane fuel (about 93). And-- avoid any brands with methanol. The lower octanes with the methanol will burn the fuel rather slowly-- so fuel can still be burning when it enters the muffler. Also, the poorer fuels cause an abundance of buildup on the valve stems and in the combustion chamber. 4. Ensure ignition timing is set correctly. I hope this helps some. David A. Sohn david.a.sohn@juno.com Saint Louis Missouri Link to comment Share on other sites More sharing options...
Guest Posted May 25, 2000 Share Posted May 25, 2000 Hello all, I just got my carb. back from the shop...did the best he could with it....i put it on and had to make some adjustment on the high speed adjustment screw.after some tinkering it now runs fairly smooth in idle and high, but it occasionaly back fires when i throttle down...it has a new plug, champion rj19lm i think....this is on my simp.3212H with a B&S 12horse,any ideas what may cause it back fire.do i have to hot a plug on there? is it still to lean or to rich?.............now to get the simp.3415h running that i recently acquired. thanks,Joe Link to comment Share on other sites More sharing options...
dlcentral Posted May 25, 2000 Share Posted May 25, 2000 Hi Joe, This is not uncommon for the back firing to happen when throtting down if the engine is hot. Is the engine hot when this it happens the most? If so the raw gas that has not been ecnited in the conbustion camber ends up ecniting in the muffler from the muffler being so hot. You may have the high speed adjustment set alittle rich but you may end up with a hesitation if you lean the jet to much. Give the high speed screw about 1/4 turn in and see what happens. Other wise I would leave it alone if it seems to perform to satisfaction As always any corrections gladly accepted and please more ideas and comments come forth best to all, >>->happyjack<-< Link to comment Share on other sites More sharing options... tej Posted May 26, 2000 Share Posted May 26, 2000 I have a B12 and a B112 both with 12hp Briggs and neither one backfires when throttling down. They will backfire if shut off from full throttle but not if throttled down before shutting off. I would check what David suggested as the backfiring is not normal for the engines. I run 87 octane gas with no problems. Tim Link to comment Share on other sites More sharing options... This topic is now closed to further replies. Share More sharing options... Followers 0
tej Posted May 26, 2000 Share Posted May 26, 2000 I have a B12 and a B112 both with 12hp Briggs and neither one backfires when throttling down. They will backfire if shut off from full throttle but not if throttled down before shutting off. I would check what David suggested as the backfiring is not normal for the engines. I run 87 octane gas with no problems. Tim Link to comment Share on other sites More sharing options...
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