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Posted by mumbles
- June 25, 2013, 00:14:27 AMIt's called a carb fart.
Make sure the carb is seated properly in the intake boot. Also do not over thighten it.
If no air leaks at the carb/intake boot then adjust the a/f screw out 1/4 turn.
Posted by Troll
- June 24, 2013, 18:28:37 PMHarleys, even injected ones, do this all the time. The official H-D explanation is called EGR crosstalk. Seems they claim that small amounts of exhaust gas are reverted into the intake tract, and this causes the pop back in the intake. S&S claims you can minimize it with a stronger accelerator pump shot and "rolling" on the throttle instead of snapping it open. When I put the Keihin blockhead CV carb on my '80 shovelhead, a little tweak to the accelerator pump linkage all but eliminated it. I had a Super E on my '98 inch Glide, and that would only do it when the engine was cold, of if I tried to pull hard from under 1500 rpm...it's a V-2 thing......Sooooo, it's maybe just a little on the lean side...but the main jet isn't the cure....the pilot is just a little small.....and the pump shot is a little thin.
Posted by greenbarn
- June 24, 2013, 17:27:59 PMOver the winter one of my projects was to do a moderate/major modification of the intake system, and to rejet the carb. I followed the "grampsizing" mod on russwolf's website, including the exact jet sizes.
http://www.angelfire.com/ak5/russwolf/documents/grampsize.PDF (I used the OEM needle, with a 170 Main/52 pilot --OEM sizes are 135/48) I know that's a lot bigger, but that's what the mod that seems to be tried-and-true suggested as a starting point, so that's where I started.
Results: everything seems great, the bike runs fine, with one small exception:
Sometimes, infrequently, if I close the throttle suddenly, and then open it again quickly, it will give a single "pop", I believe back through the carb., and usually (but not always) it will die. Most of the time this happens when rolling up to a quick stop-and-go- this will usually result in a stall, but it's happened at least once while moving down the road (but of course then it doesn't stall).
So my question, is this typical for "too lean" or "too rich", and which circuit are we talking about?
It also does smell rich at idle speeds. I probably at the very least need to adjust the fuel mixture screw: it's set at the suggested starting point from russwolf, and it ran so good there (with exception of these two little issues) that I haven't messed with it yet. Not to mention, I'm getting significantly better fuel mileage since the mods...
Suggestions? I hate to have to take off the carb, because the problems seem so non-eventful.