Detonation Problem

By Dennis Santopietro

I have a bone stock 2009 Dyna Fat Bob FXDF that has a moderate detonation problem. The bike has 5200 miles on it. If I roll on the throttle 1/2 or more the bike will ping. I am not lugging it in too high of a gear. Example 4 gear 55 mph passing a car it will ping. It has been to the dealer twice. They say its all normal and I should use a different mfg.’s of high test fuel. I have tried everyone’s gas for 2 or more tanks and it still does this. This is my second FXDF both were 2009 models, the first one was totaled in a wreck and it never pinged. Any Ideas????? Thanks Jeffrey M
  Hi Jeffrey, I would first try an octane booster and see what the results are. I have also had a number of Dynas with piston knock due to a piston being set too tight or too loose from the factory and the mileage that you have is the perfect range for this problem too occur. If the octane booster does not cure the problem instantly, they (HD) are quite aware of this problem, I would demand that the dealer repair the problem under warranty. Wrench Safe, Team FMH

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5 Responses to “Detonation Problem”

  1. Mickey

    Solution #1 Use better gas Solution #2 spark plug gap or spark plug temperature range is incorrect Solution #3 more unlikely ( due to the low mileage) but possible, timing is incorrect , (possible chain slack,tooth slippage, worn teeth,) on the bike

  2. ROBERT COULMAN

    Negative 17 degrees of valve overlap-heat from hell,etc. Get yourself an Evolution powered, carbureted motersickle-don't worry about bike night-you're gonna be ok-

  3. Ed

    Use colder heat range spark plugs it makes a huge difference

  4. Bob McCarty

    What warranty are you speaking of. The bike is 10 years old. My 2008 Jheritage is out of warranty. Please advise

  5. Daniel Morgan

    I believe they have those TCs running as advanced as far as possible then there is a knock sensor that hears the knock, retards the timing just enough to quiet it down. Maybe the sensor is failing. Don’t hold your breath for H-D to admit there’s a problem and they’ll cover it, you’ll suffocate. Everybody think back to th cam chain tensioners!!