So the throttle is no longer stuck. After replacing a few fuel lines, fuel filter, spark plugs, and tank draining the bike now runs. Sometimes it idles well, sometimes it is running on less than four cylinders.. The bike refuses to rev at all, sometimes you can sneak a few rpms out of it but normally it will just stall. When you turn the choke off, similarly it will just stall. This thing is beating me around.. The carbs have been cleaned (they are now being cleaned again), the plugs are not fouled, spark seems to be generous. It seems like it is not getting enough fuel. Any suggestions?

 

Well, I don't think there is any doubt that there is a carburetor problem. You're right, it's not getting enough fuel. The idle jets and slow jets are where your problem is. There are really tiny passage ways that are easily clogged if the bike sits for any length of time. Look closely at the inner bore of the carb, right next to the butterfly. There are tiny holes that need to be clear. Pay close attention to the small areas while cleaning.

 

unwound guitar string is an easy fix for a corked-up jet

 

This may help with some visualization:

https://cbrforum.com/forum/showpost....25&postcount=6

 

The carbs have been disassembled and reassembled for cleaning twice now. Nothing seems to change. It will start right up, however, it will not run with the choke off. It will rev up a little bit but it feels like it is trying to drag itself down. The coils have the correct resistance values and the plugs are new. Also, the main Jets do not thread completely. Is this normal?

 

That is normal for the main jets to not thread all the way in.
Have you looked into your fuel pump or adjusting your air/fuel ratio on the carbs?

 

Try stuff in this in order...

Check the spark plugs for signs of lean or rich. Sounds lean but it takes a minute to check plugs so why not. Check all of them.

make sure your spark plug wires are in the correct firing order.

Check your vacuum lines, I believe F3 is vacuum and fuel pump mix right? pump is for high speeds, vacuum for low? I think the F3 should be able to start/idle with the fuel pump not working, so the pump isn't your problem. (maybe? someone verify? i have an F2)

Is your fuel old? Fill the tank with fresh fuel.

Check to make sure your choke actually engages.

Pull the carbs again, drain the bowls (is there a lot of fuel?)

Check the pilot screws. screw them in and write down the turns on each. If your plugs were dark and wet, screw them out 1/4 to 1/2 less than they were. If your plugs were dry/white, screw them 1/4 to 1/2 turn further.

Double check the sliders in the carbs to be sure that they give a little resistance and slide back to position properly.

At this point, if you are even the least bit unsure on how well you cleaned your carbs then do it again.

If none of the above works, let us know If done right, it should run.

 

Cinderfella - I am unsure of how to test my fuel pump. I have pulled the fuel discharge line and cycled it and it seems to produce enough capacity but I'm not positive. I have not attempted to adjust the pilot screws in the carb as they should still be in the factory position.

Disserved - I will check the plugs again this evening (weather is moderate here and I'm about to go ride for a bit). The plugs are in the correct firing order. I may need you to elaborate on the Vacuum/ fuel pump, I dont know if they work together on the F3 or not. The fuel, filter, and lines are fresh. The choke is engaging. I will have to check the float bowl volume again. The pilot screws should be untouched and in factory position. The slides are moving well, slight resistance and no sticking.

 

Again I don't know the F3 well so I will leave the pump stuff to someone else. A quick check of the float bowls should tell you if you are getting enough fuel or not. You could always bypass the pump and run directly off gravity/vacuum. Your petcock should have a 2nd smaller hole for a smaller tube, if its not hooked up now, just run a tube over to the left side of your engine just below the carb boot. Should be a vacuum port there.

Is your bike stock? have you been the only owner?

You said the plugs were not fouled, but I'd like to get a pic anyway. Also perhaps a carb sync will help you.

Your bike runs like mine does for a minute. I set my bike up on the edge of being lean, and can be hard to start in cold weather, and when it does start, any bit of throttle will stall her. Sounds like you are lacking fuel but if you have a good amount in your bowls then its probably a dirty jet or poorly tuned.

 

The fuel pump on the F3 is a very low pressure pump. (maybe 2-3 psi) It basically is there as a helper as the carbs are higher the the petcock. But you can bypass the pump by running a line straight from the petcock to the carbs and it will run fine. This is what I have done. Have you checked the fuel cut relay? That was my problem at first. Wont go into anymore detail because my issue is a little bit bigger than the relay as I discovered today. But mine too would only run with the choke on and no throttle. It would instantly die with any throttle or any choke off. BUT, have you messed with your idle control screw at all? I also discovered today that mine was turned way down and that is why it would die. I let it idle with the choke on and let it get warm and as I used the ics to "raise" my rpms I would slowly back off the choke until I completely turned off the choke and had the bike idle around 12-1400. The shop manual can tell you how to do this and that it should idle around 1200 +/- 100. Sorry for the tangent but hope this can give you some direction.