Currently restoring my F2 back into shape. Recently put everything back together after cleaning, had some strange issues with the idle fluctuating up and down at about 1000 rpms either way when the choke is on. After warming up properly, the bike will idle steady with the choke off, but it's doing this strange thing!! I'll have the bike warmed up and idling fine with the kick stand down, but as soon as I set the bike upright to get ready to ride, it chokes out and die.

After this, merely pressing the ignition won't start it. I'd have to roll on the throttle over and over along with the ignition pressed down for a good 5 seconds at least before it starts up again. Cleaned and checked the carbs numerous times now and spark plus have recently been replaced with NGK Iridium plugs. We're at a lost here and can't figure out what's going on. Any ideas?

 

Could be your kickstand cut off safety thing. Just cut the two green wires connect em and bam bypass honda

 

I really doubt this is it. I notice when tilting the bike upright slowly, there would be an increase in RPM followed by a sudden bogging and stalling of the engine. I've cleaned the carbs, but should I clean it again? It sounds to me like a float bowl issue since fuel would be shifting as the bike goes upright. Did a google search and found several topics on this, but in regards to Harley's.

 

Sam, I'm pretty new at this so bare with me. I had mine apart three times so I'm just going to throw some things at ya. When you rebuilt the carbs did you take the floats completely out of the bowls? If so did you check and clean the float needle valves? Did you put them back in so the tops of the valves connect to the floats? One might have not caught on and arn't working. Did you remove the Pilot/Slow jet adjustment screws? If so did you seat them and back them all out the same amount of turns? Mine were all messed up and wouldn't run worth a crap. Did you buy a rebuild kit with all the small rubber "O" rings and changed them all out? Did you mess with the choke bar and the little plungers? The "O" ring kit has replacement rings for them. I'm finding out that these carbs are pretty sensitive but not complicated....hope this helps. I know how frustrating this can be.

 

Can it be the tilt sensor (if there is one in your year & make)

Chances are you missed something during your cleaning....also check the throttle sensor...was it reinstall correctly...

 

It's something mechanically...physical cutoff.

Because when bike is on kickstand, it idles fine, pretty revving it is fine too...

So when you tilt bike upright, something is pull/pinch/disconnect.....maybe a vacuum hose, fuel feed hose, throttle sensor wire, spark coil etc....whatever it is...careful disassemble, check service manually, checklist making sure everything in place. Also did you trim the vaccum hoses or fuel line? Length may be shorten...

 

Hey Chonburi Sam I own two f2's and one thing i have experienced numerous times is since these bikes are gravity and vacuum fed... fuel lines and vacuum hoses have to be routed correctly and having spotless carbs is always equally important as estate4life pointed out. One other thing that is just a side point and i'm sure doesn't happen unless the bike has sat for a gooooood while. On my 94 f2 it would idle and rev fine on the stand as well and when i stood it upright it would rev up as normal then bog down and die out as well. This was after the carbs were just thoroughly cleaned, and i had made sure all fuel and vacuum lines were in order, new spark plugs and made sure it had correct fresh oil and filter. I took everything back apart and as i was opening up the air box i noticed a bunch of fuel/gunk in the channels leading to the ram air tube on the right side. Basically the gunk was sitting on the left side and when i tilted the bike upright/level this chum was making it's way over to the right side and blocking the air tube. Making the bike idle down and die out. I Cleaned it all out. re-cleaned the carbs and everything is all good. Just thought i'd throw my personal experience out there. Hope you get it all figured out. : )

 

Thanks everyone for your response. We figured out the problem!! Turns out that what we thought were 2 vacuum tubes coming from the carb were actually breather tubes for each pair of carbs so the jets would work properly! After unplugging these tubes, the bike ran perfectly! Before, while the choke was on, we could not rev the engine. It would just die when applying even a little throttle, so when we made the changes and the bike revved with the choke on, we knew we got something right. I'd have to tell you, this experience brought me from understanding NOTHING about carbs to knowing it like the back of my hand. Was such a stupid mistake, but important to understand nonetheless. Rode the bike into work this morning for the first time and man... best feeling ever .