2001 FXD TC88 44.5K miles
CV40 Keihin carb
Main jet is a 180
Pilot jet is a 48
N9EY jet needle (HD part 28027-04)
Stage 1
Samson Challenger Wildcat pipes with the least restrictive baffles

Original problem: Bike was running great until I started smelling fuel and noticed slightly sluggish acceleration. I found fuel leaking from the accelerator pump diaphragm when I checked it out. I removed, disassembled, and cleaned the carb, blew it out with shop air, and installed a basic CVP rebuild kit. I also replaced the aftermarket jet needle that was in it with a HD part. I did not replace the intake to head gaskets.

No real problem with the cleaning and rebuilding and other than the kit, the only thing I replaced is the jet needle and now I am having a bitch of a time re-tuning this thing. I am getting decel popping and some occasional blowback, it takes too long to warm up and does not want to idle when it is cold and the idle is rough when it is at operating temp. The mixture adjust does not seem to have much effect unless it is turned out more than 3 turns. With that much adjustment, the popping is minimized but still still annoying. (It did not have decel pop before I rebuilt the carb).

I have a 46 pilot jet and a 185 main jet on hand and a CVP Easy-Just mixture screw and packing kit on the way because I did not pay close attention to whether or not the mixture adjust o-ring came out before I cleaned it and now I am thinking that either the o-ring went MIA and I didn't notice it or it stayed in the carb and the cleaning solution whacked it. And, I am tired of burning my hands trying to adjust the mixture using a screwdriver so I am going to put in the Easy-Just mixture adjust screw from CVP.

Before I start tearing this thing down again and going back through it looking for internal problems or swapping jets, do any of you carb experienced folks have any ideas or suggestions?

BTW, I am not looking for an EFI vs. normally aspirated engine discussion...I don't particularly GAF which is allegedly better or why because my SG has a carb and that is that. You dance with the hog you brung.

 

Not sure if this will help or not. good luck http://www.harley-performance.com/ha...arburetor.html

 

Thanks for the link. Good stuff there but the problem is that they do not present or discuss any troubleshooting points if things do not go as outlined.

 

first clue is having to turn out the mixture screw past 3 turns, this indicates a too small pilot jet, you may have to go to a 50 pilot and 185 -190 main.

also did you install the choke cable correctly, there should be some freeplay when pushed in fully, I have heard good things from the spostster needles

See attached pic of main needle, make sure it is installed correctly

 

sounds like an intake leak to me.
Did you use a new carb/intake seal ring, 27002-89?

 

If it was a non-stock needle (usually spotted by being the clip type) then it might be a dynojet kit that was used.

If so, then they have their own emulsion tube and main jet to match their needles. If you went back to a stock needle then its a mismatch.

The stock emulsion tube (AKA needle jet holder - the bit the main jet screws into) has a lot of holes all the way up. The dynojet one has just one ring of holes at the base.

If that's the case then try a stock emulsion tube and main jet (say a 180). I'd not recommend going bigger than a 47 on the pilot.

The other important thing to check from your description of the problem is the float seat and the float height.

Also make real sure that the rubber diaphragm in the carb top is not snagged or has holes. Real common for it to get brittle and/or to trap it during reassembly.

 

Here's how my 2002 FXD is set up, keep in mind the 95" kit and 203 cams. I kept the stock jets 45 and 190, put in the Sportster needle. About 2 1/2 to 2 3/4 turns on the idle mix screw. Overnight cold start 1/2 enrichener and a twist on the throttle. The bike fires right up, doesn't want to hold the idle till it's good and warm then it's potato potato all day long. Idle is 1000rpms. Pulls real good going up in the gears and has a nice little burble between shifts. It possible the intake gasket, slip on is dry and not sealing. It's possible there is a small hole in the diaphragm or the diaphragm is not seated properly between the body and cover.

 

Something's amiss if yer bike's acting lean with a 48 pilot. Put a new diaphragm in 'er & replace the intake gaskets/seals.

I'm running a 46 pilot, 190 main & '88 XL needle in my "stage 1" '02 FXD & it runs like a champ. Was pulling down 47mph with the 45 pilot, but had a lingering sneeze & decel popping. 46 pilot cleaned all that up, but mpg is down to 42 (but they may be 'cos I've been putting the spurs to it a bit more lately....).

 

I knew I would find some good answers and suggestions here...there is a lot of HD talent reading and posting here!

More on the problem...when I bought the bike it had some kind of still unidentified 2 into 1 pipe system that looks a lot like early Thunderheaders...The pipes and heat shields still looked good but the muffler was pretty ratty and even though the low end and mid range was pretty zippy, it had a slight but very annoying decel popping and blowback then. The previous owner had it rejetted with the 48 and 180 pilot and main jets with the aftermarket needle jet. I have the 46 pilot and 185 main jets but I decided to keep the same pilot and main jets since they are on target for size and replace the needle jet with the better HD jet.

I tweaked on it some more last night after I got home from work rode it to work again today. I have not had a problem starting, it fires right up with the enrich pulled full and warms up at about 2000 rpm. It is warming up and idling better and not popping as bad but it is still popping. I had tweaked it after I installed the Samsons and it did not do that before the rebuild. I also noticed that I can pull the enrich about 1/3 out and it runs smooth with minimal popping which suggests to me that it is running too lean. This seems kinda odd with the 48/180 combo. I was really hoping that replacing the mixture adjust screw and putting in a new packing kit would get me back where I was without tearing it all back down again but if I do, I have a lot of things to look for and I will probably install the 46/185 jet combo.

This is the kind of stuff that only comes from someone who knows his Harley carbs and gives me something solid to look for when I go back into it...I am surprised that this valuable pearl is not mentioned in all the info I have read and video clips I have watched on this problem. The aftermarket needle jet was the kind with the clip...it also had three washers spacing it up. It may well have been the dynojet kit and there may well be a mismatch. Since I did not change anything but the needle jet and put a rebuild kit in, this seems like a very likely scenario.

I inspected the float seat and checked the float adjustment per the manual...no problems noticed. But I will be sure to look it over real good again.

I checked the diaphragm for tears, holes, and overall condition and it looked good. I am pretty slow and methodical when I work on my own stuff and I did not have any issues reassembling the slide and cover but there is no harm to check it over again...

I was also thinking I may have a vacuum leak and I am going to check for that using the butane gas method before I pull the carb off again. When I reinstalled it, I used the carb/intake seal that came with the CVP kit. I do have a new HD seal on hand so I may swap them.

Updates later...

 

I have been micro-tweaking the mixture adjust and the decel popping is getting much better...I am concerned that I am out past 3 1/2 turns, though. I am really starting to think that that packing o-ring went MIA and I didn't notice it...I am also thinking that the previous owner never did get this thing tuned right when the 2-into-1 exhaust system and stage 1 AC were installed because the decel popping and blowback was a problem when I got it and there is a 48 pilot jet with three spacers on the jet needle. Seems a little excessive to me, but I don't have much experience with these carbs on a V-twin.

The new mixture adjust and packing kit should be here tomorrow and I am hoping that is all I will have to do. I installed my stand-by pair of new spark plugs and put some miles on it so I see how they look...