Hello! needing help with carb i have 2003 road king CV 40 carb engine is stock except for a hypercharger pro r series air cleaner and Vance and Hines true duals with thundercones. i am running the sportster needle with 195 main and 48 slow a/f screw turned out 3 1/2 from seat it had drilled vacuum port hole drilled to 1/8Th and yost kit i replaced the slide to a new slide no drilling and stock emulsion tube basically back to stock except for jetting. seems at anywhere from 40 to 60mph i can open throttle and it seems to pull some but not like i think it should has like a rough /stuttering feeling trying to excel up it takes off great from a dead stop and through gears great but at normal mid sucks when opening throttle wide open to pass or just get up speed is there something in the mid need to be changed? drop jet sizes slow and main or would the thundercones have something to do with as i read about those needing to bend tabs and such. any help would be appreciated. the jet sizes where reccommended by yost tech with their set up, he says exhaust i have may need bigger slow and back out to 3 1/2 that's where i left it after taking out their kit and still same results as it was with there kit. thanks

 

What gear(s) do you use if you want to accelerate fairly hard at 40-60 mph? It sounds like you're lugging it. If you're in 4th gear at 40mph, you won't get much pull unless you drop down to third. Same thing if you're cruising at 55-60 in 5th gear; if you want quick acceleration to pass a car you need to drop to 4th to decent pull.

If I'm accelerating fairly hard I run 3rd gear out to 50-55 and 4th gear out to 65 or 70.

 

When I built my 95" I tried 4 different jet needles; stock, another keihin needle, the 88 sporty needle and a dynojet. I also used one, and then 2 brass washers to raise the first 3 needles after running them without the washers.Finally settled on the dynojet with the e-clip on the 4th groove using the butt dyno as a gauge. Not very scientific but with carbs, that's as good as it gets without a dyno and sniffer.I tried the sportster needle like you because of Joe Minton's articles regarding tuning a CV carb but settled on the dynojet. I just didn't get good response with the sporty. With that being said, if you have a manual, I would check the float first, adjust if necessary, and then go from there. Your jetting is close, probably correct, but not knowing the altitude where you live, it's is hard to say. A 48 and 195 should be good but if anything you may be able to back off to a 46 and 190, it's trial and error without a sniffer but always change only one component of the carb at a time otherwise you can end up chasing yor tail. Aside from the carb adjustments,I would research those thundercones to see if they may be causing the havoc in your mid-range. Takes patience and alot of trial and error to get the carb right. I couldn't tell you how many times I pulled my front plug to check for rich or lean condition. BTW, when I thought I had the carb tuned about right, I went to JD's in Hellertown, Pa. for a dyno run and sniff to check the setup, running around 13.5/1 AFR throughout the RPM range after an small adjustment on the AFR screw . Good luck.

 

thanks guys i did drop down to a 46 and 190 seems to be smoother i understand the lugging did catch my self at it like a dumb ***...lol ok now i have the 46 slow in and started out at 1 3/4 turns checked plugs almost white backed out to 2 1/2 still seemed alittle on the white side now i am at almost 3 1/2 looks like a yellowish crusty start to build on plugs didn't know if that was normal though i always seen a light grayish to a tan color was good. is it possible that i need to go up to a 48 slow or shim the sporty needle everything in carb is back to stock, slide is new no drilling of the holes stock spring and the stock 190 jet and emulsion tube except for the sporty needle i dont have the stock needle as i could buy if needed is it necessary to shim a sportster needle or move up on slow jet which is easier...lol bike is stock except for hypercharger pro r series air cleaner and vance and hines true duals with thundercones. i really appreciate your guys help thus far.

 

oh btw road king hary did you drill the slide as called for or not i hear mixed opinions on it? also i'm in michigan and we are probably 850 above sea level elev. thanks again for the help did update problem now above.

 

There is a semi scientific way to get it right without a dyno. The trick is to put a stripe on a deserted country road at a telelphone pole and another two poles away. They are about 150 feet apart. Using a watch with a second hand, cross the first at 40 in 3rd gear, whack it open and count the time (or the miles per hour exactly) as you cross the second . average a couple of runs both ways. The setting with the highest speed or lowest ET is the best one. This is a fun way to do it and you can check the effectiveness of mods objectively. As allways obey all posted limits! LOL

 

Coastie56 gives some solid advice, and probably the best method to fine-tune the best jetting and setup. If you can drag your wife or a buddy out with you to do the timing, even better. I did not drill my slide or modify any of the carb parts. You probably will not have to shim the sporty needle with washers. You may find that you have to go back to the 48 slow jet and then back off the AFR screw. As far as checking your spark plugs, the way to do it is called plug chopping. You find a long straightaway that is not very busy, probably the same one you use to use the technique that Coastie describes.With a new plug, the engine warmed up, ride at wot for about a half mile, hit the kill switch and coast to a stop. Remove the plug and examine.

 

hey roadking harry how's it going today? when i had that 48 in there i had 195main as well backed off to 190 and 46 . i'm thinking that when the 48 was in the a/f screw may of been out too far approx. 3 to 3 1/2 maybe i should have leaned it out further (turning in screw i guess) till i had no black on the plugs but the yellowish crust i'm getting i rode about 3to4 miles at a time at 55 killed engine then check did this a few times till i got to where it wasn't on there as bad as the white i was getting from the 1 1/2 to 2 turns out but now at three and a half got a little seems to be a yellow tint build up on the electrode to about half across it is that still a too lean or normal look to you in your opinion? i know changing the slow is easier than getting in there to shim needle so think i'll go get more plugs and start again and work from there.

 

I'd say keep the 46 in there, adjust the a/f screw as needed. 3 1/2 turns is about as far as you can go, then you'll have to go to the 48 if you need more fuel just off idle and low speed, but the 46 should be good in a stock engine with aftermarket intake. Use the process that Coastie described to get your main jet right. The sportster needle (#27094-88) is one that many guys use. Google Joe Minton to read some of his advice for tuning the carb. He had a write-up in the May issue of AIM, same issue that Hillside's 98" build, part 1, was in.

 

You said "it takes off great from a dead stop and through gears great", so why are you messing with the pilot jet and idle air mixture? The Pilot jet and idle air mixture have nothing to do with acceleration at 40 - 60 mph.

You never answered my question as to what gear(s) you are in when you accelerate from those speeds. If you are cruising at 40 and want to accelerate quickly, what gear do you use? What about 50? What about 60?

Do you have a tach? If so, what rpm range are you having issue with?