The Dreaded Carb Fa*t
hedgehog1 said:
I've got into this topic slightly in other parts of the site but I'm strictly looking for help with this carb. Right from day one this bike has always popped through the air cleaner .... I had a dynojet kit installed with a big sucker and V&H ovals. It popped threw the aircleaner still, but was louder. They then installed a 48 slow jet and it didn't pop as much but my mileage went down to 30MPG. I then removed all the dynojet **** myself and installed the stock immulsion tube with the stock 190 main, J&P 46 slowjet, sportster needle and re-adjusted the mixture screw to 2.5 turns out. The bike runs OK but it seems to stumble a little if I'm on the highway doing 65 and I open it up. It stumbles slightly then clears up. I also still have the occasional pop if I blip the throttle too quick off idle or sometimes during deceleration if I blip the throttle to downshift. Any input would be appreciated before I end up scraping this carb and installing a Mikuni42>
Hedghog1:
I probably ought to preface my answer by saying there are at least two ways to look at this. Either you usually ride a steady crusing speed or you extract the maximum potential from your machine by accelerating, braking and downshifting your machine to increase performance. I am the latter sort of rider and approach tuning problems from that viewpoint.
From the factory, a HD carb 'pops' through the air cleaner because the mixture is WAY too lean. They all come that way. When you had the dynojet kit installed, one of the things they did (hopefully!) when they installed the kit was to drill out the vacuum hole in the carburetor slide. This is a very important modification as it makes up for the decreased vacuum signal created by the less-restrictive air cleaner/mufflers and higher air flow through the engine. When you removed the dynojet kit components, I suspect that you did not put in a new slide with the smaller, stock, vacuum port/hole. That's actually good, since you really need the larger vacuum hole in the carb slide to allow a modified HD engine run properly.
It sounds as though you're now on the right track with a #46 pilot jet turned out two and a half turns (I might try as far as 3 1/2 turns), although the #190 Main may turn out to be a little fat (I use a #185 on a carbed '05 FDX). The problem, I believe, lies with your needle. It sounds as though it needs to be 'raised' at least one notch in order to prevent the hesitation upon throttle application.
The other area I'd certainly look at is whether or not there may be an air leak in the exhaust system. If you haven't re-tightened the head pipes at the exhaust port and double checked where the mufflers clamped to the head pipes and replaced the small gaskets where the stock crossover pipe attaches (I think theTouring rigs have one if you didn't remove it to install the V&H's), you should check these areas.
You should also check intake gaskets and alignment on a TC. There is an inexpensive fixture from Harley-Davidson that will allow you to get the alignment right.
Good Luck!
PS:
Popping through the carburetor on downshifting may also be the result of a lean condition created when fuel added during deceleration by the carburetor (this is designed to keep the engine from from popping thru the carb or muffler during deceleration). I think this can significantly lower the fuel level in the float bowl and, coupled with decreased vacuum in a more agressively-tuned engine, the bike can react as if it had a lean carburetor. I also believe the vacuum-controlled "no-flood" fuel petcock contributes to the problem by not receiving enough vacuum to maintain a fully-open fuel valve, further starving the engine and resulting in the dreaded Carb Farts.
A flat-slide carb could work very well on this engine, but the lean problem may not be able to be resolved untill you replace the vacuum petcock with a manual one.