Carb backfire pain in the A _ _

[KeithKEK]

I have an 04 Road King Custom, carb model. Purchased bike with 1300 miles December 06, I installed Screaming Eagle Hi Performance Breather kit and filter along with Vance and Hines slip on mufflers and Bike was Dyno Tuned at dealership at 1700 miles (found out later don't have to dyno tune a carb model!). Problem is backfire or spitting back through the carb and some times hesitation upon acceleration. When Dyno tuned the slow speed jet was changed, however unsure what size was installed. Dealership DID NOT however make any adjustments to idle air mixture as they did not take "plug" off carb to access the idle air mixture screw. From what I have read in HD publications and articles by Joe Minton, my problem is that bike is running too lean. I have also read that the first thing done when determining the proper size slow speed jet is to adjust idle mixture. Having problems with dealer giving me a run-a-round... with various reasons such as, cold weather, possible intake leak, etc. etc. Any advice? Thanks!

[Heritage Dru]

My first thought was the possibility of a leak, but I would get all the facts about how your carb is setup first. Leaks are not real hard to check for either a can of WD40; crank up bike, spray at key points/joints and look for bubbles or a fairly dark garage and a flashlight will do -crank up the bike and aim the light at key point/joints and look for smoke in the beam. Could even be a vacuum leak in the fuel valve.

[hefitz04wg]

Not knowing how mechanically inclined ou are....I will throw this out there.

Pull the carb off the bike. remove that aluminum plug from the mixture screw. Again not knowing your capabilities..I would pull the float bowl off and see what slow jet was installed.

In lieu of pulling the barb apart, reapply the carb, air cleaner etc.. With a small srcewdriver, turn the mixture screw in clockwise(riighty tighty) until it lightly seats. Don't crank down on it. Now back it out 2-1/2 turns.

With engine warmed up and at idle, turn the idle mixture screw inward (clockwise) slowly until the engine starts to stumble. If the engine will not idle on its own during this procedure, raise the idle by adjusting the idle set screw until it does. Make a mental note of the position of the clock position of the screwdriver. Now turn the idle mixture screw outwards until the engine begins to run smoothly, adjusting the idle stop screw as necessary to maintain proper idle speed. Blip the throttle a time or two and observe the results. If the engine responds quickly with a gratifying blast and no backfiring through the carburetor, you have your idle mixture right. If backfiring occurs through the carburetor then adjust the idle mixture screw out another 1/8 to 1/4 turn. Under normal circumstances, the idle mixture screw should be between 2 and 3 turns out. Adjusting the idle mixture screw out to far results in an overly rich, low RPM fuel mixture leading to poor gas mileage and carbon buildup in the combustion chamber.



Now get out and test ride. You can tweek from there.

[ohiosuperglide]

I had the same problem with mine when I bought it from the dealer. It was to lean, once I richend it up a little it was fine, about 2 1/8 turns out, you just have to get that plug out. But I would start with checking for a leak first.. Good Luck

[ohiosuperglide]

you dont need to see the Dealer for every little thing, thats what they make you believe but not true. I know people that go to the dealer when bolts are loose like they have a special magical wrench or something, If you tune it yourself and it runs good and you know what to look for its probably right no need to spend extra money, but some people have more money than brains!!

[Okwisher]

I always run a Makuni 42mm, they are generally set up right out of the box.
Spitting thru the carb is a lean issue.