Hey all, ive got a problem with the ol scoot and maybe someone can give me some assistance. Here's the scoop.
I have a 1998 FXSTC, when i bought it, it had what looked like a carb from an 88 sporty. Anyway I rode her pretty good for the day and it started acting up, like the plugs were fouled. I pulled the plugs and they were full of dry soot. I changed em and rode some more, they did it again. Being that I bought it from IN and I live in NM, I thought it was the jets, so I changed the jets, didnt solve the problem, maybe the carb so I bought another one that had allready been modified, (drilled with the sporty needle). It made it a little better but not like it should be. So I changed the jets again, made it run a little better but still not like it should. Ive checked for exaust leaks, manifold leaks, changed jets many different times, changed the type of plugs, checked enricher for faults, checked compression and just about everything else I know to do and it still runs rich. I have noticed that if I am hot rodding around town, running it hard then it wont foul the plugs and it doesnt run as rich (still runs a little rich). But if I am cruising out on open road with the throtle about 1/4 to 1/2 open, it will quickly foul the plugs. The only thing I havent checked is the petcock, I also could be missing something else thou. Thanks for any advise..

 

what size jets are in it now? what eng. mods? need more info to make a suggestion.....

 

What kansas said plus what part of NM are you in (elevation)?

 

The jets in it now are 45 and 185. I havent done anything internally yet and as far as I know, the ppl that I bought it from didnt do anything either. Except the pipes and a k&n breather. Im not sure what kind of pipes they are (staggered, 1.5 diam, one piece, no baffels). The elevation here is around 5000ft, where I bought it was at around 800ft.

 

Sounds kinda like float level to me, check that first, it's outlined in the service manual how to check and adjust, if that is ok, you need to check your mixture screw adjustment, your motor should or almost die when you turn the mixture screw all the way in, (when at idle and good and warmed up) if it doesn't, your slow jet is too big, just make one change at a time, ride it for a while and check your plugs, you don't want to go too lean, but too rich is bad also..... check out;
http://www.nightrider.com/biketech/hd_cv_mods.htm
I have found that their Twin Cam set-ups are a bit on the rich side, don't know about Evo's though..

be sure to look of info on your Evo motor, not a TC...
Good luck,

K.

 

kansas, thanks for the reply..
I got to looken at the manual again today and checked the float according to it. It doesnt seem that it would be very accurate thou. I also changed the enricher cable, and messed with the idle mixture screw again. I screwed it all the way in and it didnt change anything at least not that I could notice. But if that means the slow jet is to big then wouldnt if I reduced it, it would run even richer? Is there a smaller jet than a 45?

 

this is a CV carb we're talking about, right? not a Mikuni or somethin' else......

 

I think JP Cycles sells a 44 and HD will have a 42

on a Harley CV carb, turning the mixture screw in leans the mix, and a smaller size slow jet restricts flow of fuel to the slow speed circuit; = leaner mixture, you might also try the stock needle shimmed up .025 - .050.

here's what I've found on my bike for example; if I run a 48 slow jet, the mixture screw needs to be about 3/4 to 1 turn out, with a 45 it needs to be about 3 3/4 turns out, but I have a 95" TC with bigger cams, etc. this would be waaay too rich for yours....the mix screw is just used to fine tune the slow speed curcuit as I understand it.

your mixture needle and or seat could be screwed up by previous owner seating it too hard.... could also have some garbage in the float needle & seat, air bleed holes could be plugged up, elevation, there are a lot of things that can cause a rich condition..... you gotta be very **** about cleanliness when you are working on/inside a carburetor.

K.

 

I'd try a 42 slow jet first, that's what should have been stock in your bike. Next I'd try a stock needle, the Sporty needle is richer all the way from the straight section on down to the tip. You don't have a Dynojet emulsion tube in there by any chance do you? The Dynojet tube has only a couple holes in it IIRC vs about 14 holes in the stock Keihin tube.

 

Hey Murphdog, what will that dynojet emulsion tube do? compared to the stock one.....

K.