I have a 2001 road king I bought used so not sure of the upgrade history. It has slip-ons and the SE air cleaner. Not sure what has been done to the carb but I assume mods were done when they did the stage 1. It runs good now.

I'm going to put a thunderheader 2-1 on this weekend and wondering if I'll need to rejet? Is there a big enough air flow difference in the 2-1 versus the stock pipes with slip-ons that I will need to tune or rejet the carb? Thanks.

 

You'll wanna rejet

 

Ok thanks. With the change I'm making would I most likely just have to bump up the slow jet to the next size, say from a 46 to 48? Or do you think it would also require a different main jet?

 

Make sure the welsh plug is removed to allow access to your low speed air fuel mxture screw. Install the pipe. Ride the bike until warm. Adjust the screw out until the idle slows. Then while counting the turns turn the screw in until the idle slows again, Back out the screw to the halfway point between where it slowed down. Ride the bike. If it spits back through the caarb it's too lean. Grab full throttle if it feels sluggish its rich, if it spit it's lean. The jets are cheap and easy to replace. You very likely won't have to.

 

if you go over to nightrider.com bike tech section there is info on tuning and modifying the CV carb.
the cv carb has the black plastic ( sometimes replaced with a chrome) cover on the top.

feel underneath, if the plug is still over the idle mixture screw mentioned above, that indicates your carb has not been monkeyed with.

It probably has, and you may want to take the time to pull the carb and see what number is on the needle and what jets are in there ( for you records)

I also replace the float bowl screws with allens so that I can drop the float bowl for jet changes with the carb in place.

the 2/1 is likely to flow more at midrange, and I would think you are correct about bumping up the low speed jet.

enjoy the new bike, MK

 

Too many unknowns. Best thing to do is just put the header on and see how it runs. you will know with in a few miles whether or not it is too far out of whack. If it is too lean it will pop and spit back thru the carb.

 

Thanks for the tips. I got home and checked and the mixture screw plug has been removed so I'm good there. I like the idea of the allens screws for dropping the float boal.

I had already ordered this kit which should be here tomorrow. I wanted to have all the parts on hand to rejet if needed once I swap the pipes. But after reading more I'm not so sure I want to mess with the emulsion tube, spring or needle jet included with this kit.

If mine doesn't have a shim under the stock needle or the XL needle I will fix that but otherwise just adjust the main or pilot and do the allen screws on the bowl. I'm not going to drill the slide hole or any of the other stuff.

I got the Thunderheader model 1025 (2-1 w/ falsie) in from UPS today and checked the instructions. Last step says "rejet your carb as necesarry. In most cases you will need to increase the main jet and reduce the size of the low speed jet." I wasn't expecting that and not sure why you would need to go leaner on the slow jet but I will have some extra jets on hand just in case. I'll let you know how it goes.

 

I finally got my thunderheader installed and carb rejetted. It went pretty smooth for a 1st timer. I'm not sure if my mixture is ideal. Maybe I will get a dyno and see. With the slip-ons and "stage 1" I was getting only about 35mpg highway and occassional carb farts. But I checked the plugs and they looked good, a light tan colored.

So I put on the thunderheader Sunday and ran it around without any carb adjustments and it seemed to run about the same to me. Granted I only ran it about 10 miles.

I pulled the carb off tonight and found it had stock needles 45 and 190 and the mixture plug was drilled and the screw was turned almost all the way in. I didn't see a part number on the needle jet. The spring appeared to be the 6" stock one. I went ahead and shimmed the needle jet with 2 #4 washers. I replaced the 45 pilot with a 46. I replaced the mixture screw with an EZ-Adjust screw. Put a chrome top on and stainless screws on top and allen heads in bottom.

On the mixture screw, both with the stock and EZ-Adjust it starts to get a little tight but still continues to turn another 1-1.5 turns before it really starts tightening down. I'm afraid to go much further for reading warnings of overtighening. So at this point I back it out 2 turns as my starting point. Fires up good, idle is high so I adjust that down let it warm up enough to push the choke all the way in. Then I turned the EZ-adjust in until the engine slows and then back it out 1/4 turn. I installed new plugs and went to take it out and it was pouring so I only went around the block a few times. It seemed to run good but not much of a test. I will try tomorrow, check my plugs and see how they look.