How do you stop spark knock in a Harley Davidson 1200?

Answer 1

You need an easier burning fuel. What it is is your fuel burns too slow or so incompletely that you're passing liquid. Your exhaust system is probably burning and corroded too. Use a higher octane fuel or an additive that'll give you a cleaner burn. Live in the midwest? Ethanol causes this too. All gas out there has it. Try 1 ounce of acetone for each 5 gallon tank. Acetone makes the fuel vaporize faster and gives you a more positive burn. Little more pep and better miliage too. Back when they had leaded gas that was a big problem with Panheads. You always had some raw gas in your pipes and mufflers and the clean air leaking in from around those exhaust flanges would make a blue torch a foot or more long out the rear of the pipes. Hard on the equipment but the little kids in the car next to you on the highway got a kick out of it. Shovelheads leak too but not as bad. You're gonna have some raw gas but the higher quality fuel you get the less ends up in the pipes.