Hi,

I've got a 2003 FXDL with ~18K miles. I got it at ~14K miles; has the stock CV carb w/ the round high flow airbox (may be stock too).. It's always run kinda poorly in colder weather (like under 50 or so), which I attributed to incorrect jetting and never thought a whole lot about it. It will sort of cough here and there at low RPM (under 2500), corrected by rolling on the throttle a bit (which I assume richens the mix momentarily through the accelerator pump). Sometimes though it would be very bad and would not even like the throttle, misfiring and "popping" when you try to get going.

This spring something had definitely gone wrong, which I attributed to the carb. It started OK but was running very quietly - missing the right thump. When I took it out on the road it wanted to stall if I touched the throttle, barely was able to accelerate etc.. etc.. (strangely though wasn't really misfiring, just running "weak")..

I rebuilt the carb, basically I cleaned it, set the float, replaced the float needle, gaskets, o rings, and accelerator pump diaphram (first shot at ordering a kit and I would not choose this kit again, would've liked to have had a main diaphram too). I set the mixture adjustment exactly the same number of turns as before..

The bike fired up and ran perfectly the second the fuel hit the carb. I didn't notice anything obviously wrong when rebuilding the carb but apparently something changed. I did replace the plugs at this time too, however the ones I took out had about 1000 miles on them and looked perfectly fine (little dry black soot is all you'd notice versus new).

The bike ran fine for a few trips around town, 30 miles or so, until one night when the sun went down after I parked the bike and it went from 60 degrees to 45. I let it warm up at least 10 minutes, got out on the road and it was falling on it's face - bucking, misfiring, etc..

So I go to adjust the idle screw - I bring it out 1/4 turn and the bike will no longer idle... I bring it in 1/8 turn, runs the same as before.. Then back out 1/4 turn and it's running OK as far as the bucking goes (can hold 2000 RPM cruise evenly) but is misfiring now when I roll the throttle (assume too rich when accelerator pump is spraying)... I go back in 1/8 turn and then it seems to be lean again. Back and forth I can't seem to get it right.

Basically what I'm experiencing is the adjustment is having an impact but it's not logical. I have adjusted things with 6 carbs before without so much trouble. Whatever is going on it does seem to be fuel related so I'm thinking some part of the carb (maybe just the stupid needle) just isn't right.. Anyone ever been here before?

I've got a repair manual (Clymer) and it's a joke, I need a better one. This one doesn't even mention the presence of an adjustment or show the needle in their diagrams. Any recommendation on a better manual?

The mixture assembly, as it came out when I took it apart, was a needle, a spring, and an o-ring at the bottom of the hole. There seems to be no seat in there, the aluminum carb body does have a taper that seems like a seat but this strikes me as fishy now - am I missing a brass seat or something? Is this o-ring normal? This is different than other carbs I'm used to.

Is it obvious when these carbs are flooding? Because of the diaphram I'm not sure what to expect, but it does not seem to be flooding. I did set the float a little different than how the manual stated because it was waaay off from how it came out and to me it looked like the float would barely open how they wanted it set. I put it in the ballpark but put err on the side of open and not shut.

Anyway, sorry for such a long post, thanks if you read this far! Thinking if all else fails gonna try to get a better idea of how to set the float, get a replacement mixture assembly, main diaphram, make the changes and try to get it running right again.

Thanks in advance!

Jon

 

It has no seat. It should be needle,spring, small washer, than O-ring.

 

Thanks - OK well problem #1 is it was missing that washer. Maybe that explains why adjusting the needle has unpredictable results, like the O-ring is getting distorted by the spring sometimes, it doesn't seal right that way and allows air in etc..

Other odd thing is I counted 5.5 half-turns when removing it, and that's about where it's been running OK (or in other words 2.75 full turns).. Poking around online about how to initially set the screw I found two places saying 1.75 turns - maybe that's just a matter of it missing the washer (ie washer thickness is about 1 full turn).

Ordered a kit with the ez adjust and packing.

Thanks,

Jon

 

Without that tiny washer between the o-ring and spring you can't be guaranteed a good seal so your mixture will be unpredictable... explains the odd results when trying to adjust it. Unfortunately, the washer, o-ring, spring and needle are not available from HD since these are not supposed to be 'serviceable' components by EPA rules. I believe you can get the components from CVP or DynoJet. EDIT: LoL! never mind... you already got all that!!

One thing you may want to confirm is that both cylinders are firing when the engine is acting up and feels like it's going to fall flat. My bike is currently fouling a plug once in a while and runs like crap when only on one cylinder.

 

That screw adjusts the slow speed and idle mixture. I think you need to step up two sizes on the main jet.

 

I never really messed with changing jets on anything - how do I know what I've got and what to try? Is having to change that main jet typical?

At what point is it a high speed versus low speed jet problem?

Thanks,

Jon

 

Running oddly, for sure. I have an '04 FXDP, so same carb, & took me a good while to dial it in.

Exactly how did you set the float level, and to what? That's pretty critical in my experience. Setting the float level on this carb is a bit of an odd procedure, as described in the service manual. Have to lean it up at 20 degrees from vertical, then measure bottom of float off carb body surface with bowl removed (0.413"-0.453" spec with valve barely closed).

Also, what jets are you running and how many turns out on the mixture screw? If you pull the jets, the size should be stamped on them. At least with mine, it had the OEM jets which were 190 main & 45 slow with everything stock. Wouldn't run worth a crap. Backfired & popped bad on decel. Replacing the 45 with a 46 slow solved that. Then when I installed a DK Customs open AC, I had to push the slow to a 50, and the main up to 195 before it would run right. Pretty finnicky.

Are you sure you got the slide diaphram back in the groove correctly before you put the cap back on? And are you sure it did not have any tears or holes? Carb rebuild kits typically don't, in my experience, include a new diaphram. Mine is the original with 55K mi on bike, & still works fine - IF I get it back in properly.

 

Thanks - I did read the plugs when I removed them and seemingly they were the same. Is it obvious when one of these gets fouled or how do you verify both cylinders are firing otherwise (ie by reading plugs or spark test?)... Are you dealing with a mechanical or electrical problem?

My thinking (maybe wishful) is since the bike runs perfect in warm weather but not colder, is it's practically a dead ringer for carb issues. Did also order a new large diaphram and a CVP velocity needle that supposed to make it a little richer mid range. When the odds and ends show up will set the float again and swap those parts out and hopefully that's it.

On the needle/packing, the silly thing is they have a little rubber o-ring in there that probably will not stand up well to even just carb cleaner. The clymer manual is a joke, they will dedicate pages explaining how to remove something obvious like a throttle cable but not a sentence on adjusting a carb or even a complete carb parts breakdown.

Jon

 

I assume the jets are stock but will read when I take the carb out to replace these other parts. I took a look at the diaphram and it looked OK but was very flimsy and may have been damaged somehow I didn't see.. it didn't look like the type of thing you'd ever re-install when rebuilding a carb. It was installed correctly though.

The jet was set initially at 2.75 full turns out - which is where I found it. Now it's probably 3 full turns out.

On the carb float - I set it just above the high end of that spec (believe I decided on .47), because it didn't look right any closer to mid-.4.. When I took it out it was actually much higher (like guessing .6) - looking online though I see other places saying to set these carbs with the float parallel to the body (when the float is just touching the spring on the needle).. That would be similar to how mine came out, where the Clymer manual I don't trust was saying to set it so it was angled down when compared with the body (ie slanted down from the end with the needle)..

How does your float look when compared to the body when you set it at ~.4 ? There's definitely a descrepency there because I found two different ways it's documented and the results are much different. If it runs well for you like that maybe I'll try it with the funny angle and it will run better (although I swear it's gonna flood like that).

Thanks,

Jon

 

I just used the float adj procedure described in the HD service manual. Seemed to work perfectly for me both times I've replaced the needle valve & adjusted it. Don't know any other way.

My slide diaphram is the original. I'm absolutely sure the carb on my bike was never opened up before I got it. I see no reason it shouldn't last the life of the bike. Unless I really screw up, that is (a not unheard-of occurrance).