What would cause mild backfire

Discussion in 'General Harley Davidson Topic' started by ironmark, May 3, 2009.

  1. ironmark

    ironmark Junior Member

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    I have a slight backfire in my bike coming from the front cylinder on decel only , it makes a light poof sound not a loud bang or popping . It started when I had the 103 stage 2 installed & the dealer said that when I had the bike dynoed it should be tuned out . It was getting around November & it was time for me to head out to Las Vegas for the winter so when I got to Vegas I went to HD dealer & had them do a custom mapp . The bike still made the slight poof noise , I took the bike back to the HD dealer that did the dyno & told them about the backfire , They took the bike back & said that they put it back on the dyno & said the bike runs to good to change anything , by the way I did change the exhaust crush gasket & it made no difference . I am used to it so it dont bother me much but a friend told me that I should try to get it taken care of because it could lead to engine damage . What would cause the noise was it the big bore install or is it fuel-air mixture problem ?
     
  2. ironmark

    ironmark Junior Member

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    The exhaust is tight I just check it a few days ago , I like to check everything I can when I change the oil & the Vance & Hines big shot true duels has no seams , it is 1 complete pipe front to back for each cylinder . The bikes fuel-air mixture being set so lean it would not seem that there would be any unburnt fuel in the exhaust pipe . My friend has a 07 classic with the 103 stage 2 with rinehart slip on exhaust & he had a bad exhaust leak so we tighten the pipes up today . His bike has not been dynoed yet & his bike does not have any backfire issues even with a exhaust leak .
     
  3. ironmark

    ironmark Junior Member

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    Well I am assuming that the bikes are set a little lean now adays , my spark plugs have a nice tan color & I get great mpg,s but I do get some spark knock when the engine is warmed up & the bike is working hard . Like you said Hobbit maybe it is the nature of the Vance & Hines exhaust .
     
  4. ironmark

    ironmark Junior Member

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    I have the stock 96" heads on my bike , I was looking for low end tourqe not speed , the bike goes fast enough . Thanks for the info & I will leave everything as it is & just ride the bike . The reason I was asking is because I am heading back to Michigan for the summer & if it was a dyno issue I could still have the issue addressed while I am still in Las Vegas where I had the dyno done .