I thought some of you might like to see this if you haven't seen it before:
Note: "Fuel Screw" and "IMS (Idle Mixture Screw) are the same thing. Keihin uses the terms interchangably depending on what information you are reading.
Part numbers for different needles:
Sudco Part numbers:
Main jet part numbers:
Here is a great webpage detailing the location of all the jets and adjustments on FCR's - I'll do the same with my bank of 39's (with better pics, of course) when I pull them apart next time (should be next week - I'm going to skinny up my slow fuel jet just a bit and give them their annual cleaning).
Since this is stickied now ...here are some shots of the innerds of the beasties (Keihin FCR39 flatslides)
Underside of carbs with bowls removed...you can see the emulsion tubes (8MM unscrews them) and the main jets (6MM unscrews them). The lone silver rod is the accelerator pump actuator.
In this shot, the brass is the main nozzle tube with a main jet screwed into it.
Other holes (in relation to brass you see) are the pilot fuel jet at the 7:00 position and the Idle mixture screw at the 3:00 position. There is no jet in the hole at the 12:00 position. The float needle is at the far left.
Another shot of same with flash so you can see the pilot (slow) fuel jet. I have already removed the Idle Mixture screws in this shot:
Here is a shot of the top of the carbs where the needles live:
Close-up of screw that holds needle in place:
Screw removed, showing top of needle and the C-clip. Notice - no plastic spiders, springs, rubber diaphragms, or other crap to mess with. Simplicity at its best. I LOVE FCR's.
Here is a close-up of the pilot (slow) fuel jets. Location documented in above shots.
Closeup of the main nozzle tubes (these screw into the carbs, then the main fuel jets screw into these). Main fuel jets partially in view at top of shot.
Closeup of the main fuel jets. Emulsion tubes partially in view at bottom of shot.:
I use small needlenose pliers to remove the needles:
Here they are removed:
Here is a view of the back of the carbs...you can see the red plastic intake trumpets, and two brass jets at the base of each spigot. The brass thing on the left base of each is the slow air jet (it is a spring loaded screw) and at the right base location is the main air jet:
Close-up. Again, slow air jet on left (adjustable spring loaded) - main air jet on right (choose a fixed number):
Accelerator pump actuator rod:
A ball-socket allen wrench is a must-have to undo the screws that hold the trumpets on - that or you can Z-bend a normal allen in your vice. 4MM is the size:
Close-up of slow fuel jet removal:
Close-up of main air jet removal:
A can of carb soak for making all those giblets I removed look new and clean again:
All shiny and sparkly again...now I just shoot carb cleaner from a can through all of them before re-installation.
Here are my aftermarket stealth racing adjustable Idle Mixture fuel screws:
As far as cleaning the carb bodies themselves...I jam the slides open with a screwdriver, protect the bike's faster green paint with lots of towels, and then spray carb cleaner into all the holes:
1) Main jet/main nozzle tube hole
2) Pilot fuel jet hole
3) Idle mixture fuel screw hole
4) Slow air screw hole
5) Main air screw hole
6) Other hole next to main jet / main nozzle tube hole that doesn't have a removable jet that lives in it.
7) I make sure I see a nice stream of carb cleaner come ouf of the two holes that are in the base of the carb throat.
8) I dis-assemble the accelerator pump and clean it as well, being careful not to lose the two rubber O-Rings or the spring. I have contributed to another thread with lots of pics on accelerator pump mods here:
Avoid getting carb cleaner on your FCR39 logo - it will destroy the paint and you will have to have Giannis make you a new custom one. Ask me how I know this.