Stock Jet/s?
#2
Did you do a jet change previously? I'll continue as if it was like that when you got it.
What did you put back on, stock or aftermarket mufflers? If it ran good with the Straight Shots, it must have a size larger low speed jet in the carb. A high speed jet change is seldom needed, unless you like running near redline a lot.
Have you checked the bottom of the carb (might need a small mirror) to see if the mixture screw plug has been removed? You can adjust the mixture screw for smooth running with both stock or most aftermarket mufflers with a size larger low speed jet.
Aftermarket pipes with stock (very lean) low speed jets often stumble and backfire at low rpm and sometimes when backing off the throttle. The decrease in back pressure with low restriction pipes leans out the carb mixture, and from the factory, they're about as lean as they can run smoothly. There are more complicated ways to set up the carb for ideal performance, but a simple size up low speed jet and mixture screw tweak will do well enough most folks probably wouldn't notice the difference.
What did you put back on, stock or aftermarket mufflers? If it ran good with the Straight Shots, it must have a size larger low speed jet in the carb. A high speed jet change is seldom needed, unless you like running near redline a lot.
Have you checked the bottom of the carb (might need a small mirror) to see if the mixture screw plug has been removed? You can adjust the mixture screw for smooth running with both stock or most aftermarket mufflers with a size larger low speed jet.
Aftermarket pipes with stock (very lean) low speed jets often stumble and backfire at low rpm and sometimes when backing off the throttle. The decrease in back pressure with low restriction pipes leans out the carb mixture, and from the factory, they're about as lean as they can run smoothly. There are more complicated ways to set up the carb for ideal performance, but a simple size up low speed jet and mixture screw tweak will do well enough most folks probably wouldn't notice the difference.
Last edited by Imold; 05-03-2016 at 08:46 PM.
#3
#4
If it's not backfiring or stumbling at low rpm, I doubt the carb is causing vibration. Is it a steady vibration that changes with rpm, or irregular, with changes in throttle? Does it vibrate the same sitting still, or steadily increase with speed? Excessive vibration is usually something mechanical, possibly ignition related but not fuel related. You could check the plugs; if the carb had been set up wrong, the plugs may be fouling and misfiring, but I think you'd be able to tell the difference between misfiring and mechanical vibration.
A jet change is fairly simple. The sizes are stamped on the jet, so you could match what you have in there against stock numbers. I'd recommend against going with other than stock for the main jet, but stock or even a size up on the pilot jet should adjust out just fine with the mixture screw using stock mufflers. You should get a bit more power in the mid rpm range with stock mufflers, too, wide open pipes are best for high rpm, not where you spend most of your time with a Harley, unless you do a lot of other work on it besides the pipes; in near stock configuration, they run better with some back pressure in the pipes.
Here's a page that has some good info:
http://www.harley-performance.com/ha...r-jetting.html
#5
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