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Workshop => Carburetor, Intake, and Exhaust => Topic started by: dirtyd on April 26, 2015, 09:40:54 PM

Title: whats causing backfiring?
Post by: dirtyd on April 26, 2015, 09:40:54 PM
I'm getting fustrated. Since last summer my R hasn't been running right in the middle. Starts and idles fine but when giving it throttle it starts to stumble before coming onto the pipe and sometime back fires and once it runs on the main it runs good. Iv'e got  38mm A/S DGH needle and tried every position, 48 pilot 180 main. Fresh gas 50/50 mix race and premium. I am wondering if its electrical like maybe the coil. I swapped out stators and cdi (all OEM) and new spark plug wire. I didn't have a spare coil so thats my last hope maybe unless you think its jetting. Any help would be great.
Title: whats causing backfiring?
Post by: Victork on April 26, 2015, 10:49:38 PM
Did you do a plug chop?
Title: whats causing backfiring?
Post by: udontknowme on April 26, 2015, 11:17:26 PM
back firing seems like it would be caused by a premature spark. malfunctioning cdi maybe
Title: whats causing backfiring?
Post by: dirtyd on April 27, 2015, 08:14:50 AM
Tried a couple cdi's and stators with same result. Was thinking coil but someone was telling me they thought a coil works or it doesnt, is this true?

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Title: whats causing backfiring?
Post by: Jerry Hall on April 27, 2015, 11:30:57 AM
Quote from: dirtyd;53733
I'm getting fustrated. Since last summer my R hasn't been running right in the middle. Starts and idles fine but when giving it throttle it starts to stumble before coming onto the pipe and sometime back fires and once it runs on the main it runs good. Iv'e got  38mm A/S DGH needle and tried every position, 48 pilot 180 main. Fresh gas 50/50 mix race and premium. I am wondering if its electrical like maybe the coil. I swapped out stators and cdi (all OEM) and new spark plug wire. I didn't have a spare coil so thats my last hope maybe unless you think its jetting. Any help would be great.

Is the backfiring noise coming from the muffler or the intake?
Title: whats causing backfiring?
Post by: dirtyd on April 27, 2015, 03:33:41 PM
That im not sure. I assumed from the muffler. Are you thinking reeds? But once it gets past the stumble and is reving out it rips.

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