Backfires when engine shuts off

bkmarsha · Posted: August 2, 2008, 12:39 pm Post subject: Backfires when engine shuts off

recently got a 78 650 special that was not running

now i have it running well and when i shut off the engine it backfires once 1-3 seconds after the engine has been killed

any recommendation would be great doesnt affect the ride-ability just annoying

xsjohn

Fuel in the exhaust........check the plugs ......are they black.......xsjohn

bkmarsha

plugs have some discoloration but are not extremely dark

BigGeorge · Full Member Joined: Apr 13, 2008 Posts: 267

Like xsJohn said, unburned fuel is getting into the exhaust and the hot exhaust is igniting it. Is your idle set too high so that after you turn the ignition off the engine continues to turn over for a few seconds? Try shutting the bike off by letting the clutch out and stalling it in gear and see if it still happens ..................BG

bkmarsha

new update

i have turned down the idle and that helped the backfireing a little

just the other day i could not get it to start and found that i had fouled the plugs... put in new plugs and started up on the first kick

what can i do to solve this problem and could it be related to the backfireing situation

thanks for your help

Retiredgentleman

A couple of things you should tell us. Have you cleaned the carbs and/or rebuilt them? Have you set the points gap and verified with a timing light?

bkmarsha

i did clean the carbs when i got the bike maybe a month ago, replaced all of the fuel lines, and have ran two tanks of gas through it that i had added carb cleaner to

i have not set the points gap or verified with a timing light how is this done

i wonder if it is just a problem with the fuel to air mixture

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