Back Firing Between Shifts


Got a question about my 2000 Hertiage Springer. When I put the striaght pipes with the narrow shark fin tips on, the bike will backfire between each shift. And back off some when downshifting. At night some flame can be seen from the R/H pipe. (stock headers) My bike is normally asperated (Stock Carb) and I have a K & N air filer. When I slip the Samsons on it doesn't backfire. I did a plug chop. (Old style of checking fuel/air mixture) and the plugs were slightly black in cool weather. Started with new plugs for test. A local wrench, who looked em over said it was fine and when the weather got warmer it would lean out a bit more. Said he perfered to run a tad on the rich side for better cooling. He also said the backfiring was caused by raw gas get into the exhaust header and pipe and igniting and would cause no hard to the engine. Does this sound right to you guys?? Thanks Mac2000HS
The straight pipes are the problem here, they reduce back pressure and the engine will loose power because of this. The popping in the pipes is the result of the lower back pressure and it will actually run on the rich side with less back pressure.

I had a friend that installed Rush slipons with the 2 1/2" baffles (he liked noise) and he couldn't get the bike to run right after it warmed up. Finally I convinced him to go with a smaller baffle and it cured the problem.

You could try the Big City Thunder units in the pipe and it will not change the sound much but it would run better if you want to keep the straight pipes. They will give you the needed back pressure.

Big City Thunder - Product Fit
Thanks for your help Glider. It does sound kind of cool, but I'll either do what you suggested or put the Samsons back on. Also leanred something about why my 88B needs 5 micron filter rather that the 30 I've been using. Read your post concerning that topic. Thanks again. I'm glad I found this site.
While I'm on a roll here, I would like your opinion on another mod that I did. As you know the crankcase pressure is vented thru the rocker covers and directed to the breather backing plate via hose where it is hopefully drawn into the intake. And as you also know not all of it goes to the intake and you wind up with an oily mess dripping from the inside of the breather cover. What I did was place a 1/4" piece of copper tubing on the backing plate and conected the rubber vent hose to it. I then routed the tubing around to approx. one inch from the ventura openning. Now all of it recycles thru the intake and not one drop leaks out. Is there anything wrong with doing it this way. Your advise and opinion is appreciated.

I've done what you mention here on EVO's and it worked well making an inverted "L" with a 45* cut on the end over the intake.
I would try to find why you are venting the oil that you are venting too. Are you running the engine over full on oil which can cause this problem? Maybe try shorting the oil a few ounces on the next change.
Take a peek at this post which deals with the TC engines.

Oil Carryover To The Air Filter - Harley Davidson Community

You may also want to check/replace the umbrella valves in the rockers in some cases.
While double-checking the umbrella valves, drill out the drain hole to drill number size 42 which is 93 thousandths of an inch. This is to make sure there is no buildup of oil waiting to drain that might overflow into the breather hole and down into the air box and out all over your engine.

Also there's the option of venting to the atmosphere instead of putting oil into the intake that would cause carbon in the cylinders.
Thanks for the info. I read the articles. Sounds like venting into atmosphere is the easiest way. Actually is wasn't a lot of oil. Just over time it got to be a mess. Was the worse after a long hard ride. Didn't think about the carbon. Figured the little bit of oil would help the valves. Its been a problem with HDs for a long long time. The umbrella valve is about as close to solving the problem as they have come. Mac2000HS