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I purchased a 1990 FXSTC with 11K miles. Great shape but it had a HyperCharger but a pristine SE backing plate, filter, and round cover in the box. It also has V&H Long shots on it for reference and no other mods.

I removed the Hypercharger and had to pull the carb to remove the T fiting from the VOES vaccum line so I thought I would go through the carb and make sure everything was good and clean. The inside didn't look too bad with this crap fuel that we have. The jets were not gummed up which is good.

The air fuel screw was at 3 turns out. The slow speed is a 45 (had to get my son to read it as I couldn't see the numbers!) and the main is a 180. It has some kind of kit installed as the needle is adjustable and the clip is in the 3rd position from the bottom out of 6 slots (I remember there being only 5 slots in the dynojet kits and the clip went in the middle - third from top or third from bottom yielded the same result). The emulsion tube only has two small holes towards the base where the main jet screws in. I have some other Keihen jets in my stash and these don't fit into the emulsion tube - the threads on the ones I have are bigger. So I am not sure if that emulsion tube/main jet are stock or if those jets are from some other bike/ATV that I have owned in the past.

SO what is the baseline jetting starting point for an 1990 80" Evo with stage 1 pipes and air cleaner?

 

A 45 at 3 turns sounds typical and a 180 is ok for the most part. I prefer a 48 low so you have more "range," as the idle screw actually changes a bit more than just the idle mixture and a 185 might be a bit better if you do a lot of high speed cruising. Depends how you ride and what you're looking for as far as throttle response/drive-ability/fuel mileage but you're basically good on jet size.

 

I have a 48 slow speed in my spares - I may throw that in it and see what that does to the idle mixture screw.

I will run the 180 for now and see how she runs. Just trying to get her back on the road and get it inspected for now.

 

Cool. A 48 will use about 2 - 2 1/4 turns off seat most often.

 

I think the Dynojet emulsion tube will not accept Keihin jets, so most liklely thats what you have, so you have to use Dynojet jets. CV Products emulsion tubes accept stock Harley jets as well as their own brand of jets.

 

What about that needle?

 

Well, full disclosure - I spent every weekend for 2 summers and one winter when it wasn't snowing, doing every mod to a CV that you can imagine in all temps, weather/riding conditions. So in a way, I may know too much about those things (laughing). I don't know everything but what I learned was by actually riding rather than going by dyno readings which is fine but can't duplicate elevation and weather changes. If you started bone stock and asked what a particular change will do I could probably tell you. But, it's all with stock heads. Ported is a totally different ball game and I can't help much with those.

I agree with RT, it's probably had some Dyno jet parts installed. Harley even marketed a version of that kit under Screamin Eagle some years ago. One version had tube, jets, adjustable needle and another version had different diaphram springs.

There's a wide overlap on these carbs (idle, mid-range, high-speed, wfo) Anything you do will ultimately, sometimes drastically affect the other so again, just depends whether you want a bar-hopper, high-speed cruiser or general knock around ride and whether fuel mileage is of any consequence to you. I'd recommend you check the hole in the top of the slide to see if it's been drilled out. If anything bigger than a 7/64 drill bit will fit - replace it and I'm no fan of adjustable or shimmed needles on the HD CV but they'll work ok . Unless you're ready to go back to the stock type emulsion tube, just leave the adjustable in it for now. (clip in 2nd notch from the top) Many recommend the early Sportster needle (27094-88) but I never got any mileage with one because it came into mid-range a little early. There's also a chance the slide spring was changed but I don't have the measurements handy for you to check that. The Dynojet springs are near stock length but lighter and the SE versions are shorter about same pressure as stock. I'll go measure some if you want, but it'd be later this evening before I go to the shop. I like a 48 low jet because it allows more range in tuning to the needle/tube. Actually with what you have, 1.5 may be all you need on the screw with a 48 but 3 on the 45 is typical with what you presently have.

I'm overly caffeinated today... heaven help us all

 

Try some Death Wish coffee.... yee ha!

 

45 or 48 and a 180 or a 185 are good numbers to start with. If the plugs look good with the latest air filter then leave it as it is. Consider picking up a new stock or cvp emulsion tube, needle, and needle jet. Don't need to change them out right away, but nice to have if you decide to later on. YD