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| decelerating back fire http://mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=73316 |
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| Author: | Paulo985 [ Fri Dec 07, 2018 8:27 pm ] |
| Post subject: | decelerating back fire |
I am new to a 2012 model GTR with a stock 35 hp Vanguard. My question is if it is common for these motors to backfire when letting off the gas from a higher RPM. If this motor decelerates quickly it backfires. It idles well and runs well reaching about 4100 rpms before the rev limiter kicks in. I have read that the cost of upgrading to a Mikuni carburetor is about 700 dollars and am curious about what besides a more responsive throttle are the advantages. Higher speeds? More power? More efficient? Any input would be appreciated. |
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| Author: | MNGunner [ Fri Dec 07, 2018 8:44 pm ] |
| Post subject: | Re: decelerating back fire |
Mine has always backfired when coming off throttle quickly. Not that that makes it OK or normal (experts can weigh in on that). |
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| Author: | Will C [ Fri Dec 07, 2018 11:58 pm ] |
| Post subject: | Re: decelerating back fire |
2 things. A leaking exhaust gasket or a crack in the exhaust will do this. Even a hard to see crack in the flange. It pulls in that cooler oxygen and will pop. Second is being too lean on idle circuits. I would clean the carb making sure the pilots are perfect then remove the idle fuel adjustment screw limiters. Set the idle fuel correctly and I bet the backfire chills out. |
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| Author: | Paulo985 [ Sat Dec 08, 2018 8:39 am ] |
| Post subject: | Re: decelerating back fire |
thanks for that information, I will have the carb taken care of and inspect for cracks. Do you think the running lean and other points need immediate attention or can I safely run until after season is over? Is there a fuel additive that may help?The engine has performed well so far except in one circumstance where I got totally stuck and had to do some serious digging to get out. The motor stalled and I probably flooded it trying to get it restarted.I waited a few minutes and it started back up and we dug out. Like some others on here I often resort to choking it momentarily to get it started even when the engine is warmed up. I think part of this is my own inexperience ( stupidity) with these motors. I was a die hard Pirog guy until my son convinced me to get a surface drive. I had a fuel supply problem because of the quick connects at the tank which is twenty feet of fuel line away. I eliminated the quick connects and now my fuel filter stays primed and no bubbles. |
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