When you are holding the throttle steady and it starts popping, what is your throttle position?

 

1/4 close to 1/2 throttle

 

Generally speaking that is your where your needles provide fuel. I wonder what would happen if you raised them one notch.

 

No notches I'm forced to use shims. I've got 2 shims under each needles as of right now. I'm hesitant to keep adding shims but I may just to see if it helps

 

I think that you are safe to at least try it. It won't do any damage and it is a relatively easy thing to try.

 

I was going to "guess" that now that the carbs are clean, your getting too much fuel.
I was going to say, remove 1 set of shims. And maybe turn the mixtures in a 1/2 turn.

But it's really hard for us to know what your bike wants over the internet without hearing it.
This is also why dyno tuning is worth the money. Then you aren't guessing at mixtures & ranges.

 

Im with Phil on tunning over the net but would look for dynojet stage 1 needles if you get it right with stock needles and shims... they have a a nice taper that works great on the F2.. a really nice broad mid range will be had..

 

New to these bikes. Do they have rubber boots between the head and carbs ? If so check them for cracks. I look back over the years and remember giving up on some really cool bikes I owned. Rebuilt and synced carbs but still ran weird. Turns out they all had cracked carb boots letting air into the air/fuel mix. Now anytime I pull the carbs, I replace the boots with new ones. Cheap insurance and one thing less to go wrong.

 

My boots were rock hard and after this many years if yours were never replaced, I'd say you want new ones.

Now I've been chasing your same problem and I think it's due to the jetting in the end.

What I finally put together so far is if I rip on the throttle, it bogs down. If I go ***** out it gets worse and actually stays running bad for a bit. Eventually everything comes back to normal and I can still pull high speed and high RPM but ONLY if I am casual with acceleration or while it's cold. Mid range appears to be the source of the issue since that's where most of the work was done.

So my assumptions is I'm dumping too much fuel in since that's the only thing that the throttle controls that would NOT be momentary like air intake. With a heavy twist and hold, it just keeps flooding it vs. a quick rip floods it momentarily. Mid range again seems the be the only issue since the light rip is in mid range to reach top end and it sputters but leads out with power. If I just kept holding it, it feels flooded and just runs like crap for several seconds (consuming flooded fuel) and finally zips out. It can actually be violent if I ease off just right.

The end hypothesis based on assumptions and the replies here is I think it's the way it's jetted and I think it's the mid range so I gather that's needles and I need to probably start at the lowest setting and pray otherwise find a factory set as other's suggested.

At least with new boots, it won't be the ultimate work out that requires an engine hoist to assist in removing the carbs with the rock hard boots Wrist is still messed up 2 weeks later...

Curious how your results go and I'll reply with mine assuming we have the same story

Quick add, we thought it was vacuum leak but I plugged all possible sources except the charcoal can (Cali bike) and the issue remains in 100% the same behavior.

 

Phil314 for the win!
Took out a set of shims an leaned out mixture ever so slightly. Now I can cruise, I can RIP it ; no bogging or popping unless I get excited an rev the **** out of it at a stop lol (I'm 26 ) but this Saturday is the true test as I'll be out riding the majority of the day.
Curious to see how it does after fully warmed up.

Also about how long until your bike is at operating temp? Mine never gets above half on gauge.