backfiring at low rpm mixture screw question

miller0613 · Full Member Joined: Jun 27, 2007 Posts: 111

My bike has developed this backfire after about five minutes of riding if I leave a stoplight or something and I have to ease the clutch out ridiculously slowly to keep it running. The plugs look pretty good maybe a little rich. Could the mixture screws be too rich and this is what is causing this? And on the mixture screws in is leaner correct?

schtipp

my bike was just doing the same thing. i had to keep the rpms above 2K and feather the clutch to pull out, but after that it ran well at speed. chased my tail for a while. i cleaned my carbs, re tuned them and synced them. ran a couple tanks of sea foam i just couldn't get it rich enough at idle.
i'm still not 100 percent wht fixed it, because I was doing everything. but it seemed like running it opened something up. one at a time the cylanders richened up. it's tough to get a plug read for the idle end of things. i can tell you that if it starts real hard and needs choke even when it's warm, it's probably too lean of a mix.
and yes ,in is more lean on the screws.
count how many turns iut the screws are from the bottom before experimenting, just so you'll have a frame of reference.

schtipp

also, check for a vacuum leak around the intakes.
spray some starting fluid around the suspected places and se if the idle changes.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

deleted

jerseykat1 · Full Member Joined: May 03, 2009 Posts: 79

sounds like an air leak.

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