I've got an interesting problem... While cruising, if I pull the throttle just barely off the bottom, the bike surges ahead for a moment then hesitates and then picks up again. RPM doesn't seem to make much of an impact.
I've noticed as well that when pulling on throttle, it's very difficult to go from decel to accel smoothly.

It's a 1994 F2
Vance & Hines 4-1 exhaust with pipe
K&N Air Filter
DynoJet Stage 1, second clip from top plus one washer, fuel out 1.5 turns, and DJ126 Main Jets
note- the problem was also present before the jet kit

Any help would be awesome

 

Just to clarify, was it AFTER the exhaust and BEFORE the jet kit?? It sounds like a needle adjustment problem. I'd drop clip down to 3rd clip pos. from top. That's usually where most people start off with. See how it reacts to that. Also, 1.5 turns out on fuel screws isn't very much (about where stock setting is). How does it start cold? If raising needle helps, I'd go back and play with fuel screws.

 

I bought the Bike with the Exhaust and filter. It had a few dead spots at 2000 and 4500, plus the throttle issue. I bought and installed the Dynojet kit today. Pretty much cleared up the dead spots. But the throttle issue remains... Cold starts require choke, even not so cold starts, but starts fine hot.I'll give the needle raise a shot tomorrow. Thanks

 

My bike always requires choke when starting cold or even semi cold. It's a pretty standard thing!


As for his settings, those are stock for the dynojet. I went out to two turns on mine though due to a lot of popping while engine braking pretty much from 6.5K down.

As for going from Decelerating to Accelerating, it could be related to excessive chain slack, or perhaps just bad throttle control. Depending on whether you're engine braking or accelerating, you'll have the slack on different sides of the chain, and in switching that chain has to switch where it's slack is as well!

Check chain slack, and also look into being a bit smoother in that transition from decel to accel by using the clutch a bit perhaps.

If that doesn't work, report back, we'll keep investigating

 

A good rule of thumb for adjusting needle height is this...In 3rd or 4th gear, run it up to 3-4Krpm's and while at steady throttle, crack it wide open. If it pulls away cleanly, needle is in acceptable position. And I agree with Jesse, it should require choke for cold starts. For the fuel screws, this is my preferred method of adjusting them. I have an old multimeter that has a tach function on it. It doesn't read correct rpm's but it does read them in 50 rpm increments and that's what's important. With it hooked up, I back fuel screws out until rpm's drop, then screw them in 1/2 turn. It's slightly on the fat side on bottom end but not enough to foul plugs or anything and it really helps throttle response (especially if at dragstrip or trying to blast somebody from a redlight). Don't try it with the bike's tach, it isn't sensitive enough to read that small of an rpm drop. Again, just my .02

 

Interesting technique! I'll have to try that sometime... Where exactly are you connecting the leads?

 

I hook pos. lead to negative side of coil and neg. lead to a ground (frame). I bought that thing at a yard sale forever ago. It's the old black one with clear cover on front and red needle sweep, remember those? I haven't used it in a while but if I remember right it reads somewhere around 1/4 or 1/5 actual rpm's bike is turning. All I care about is noticing tiniest of rpm's drop so I don't care what it's actually reading. You could get away with the bike's tach if there was a way to back out all 4 screws at same time.

 

Well I tried dropping the needle one slot. The hiccup disappeared, but a huge flat spot @5000 developed and it wouldn't push past 10K. So I went to the top clip. Pulls like a banshee, but the hiccup is still there, and cruise developed a slight stutter. Tried 1/2 turn rich on the mix screw, no real difference. One turn lean, and the problem got worse. Back to original, 1.5 turns out.
I'm thinking of keeping the needle where it is but adding the washer from the DJ kit under the clip. And maybe a full turn rich as well?
Thanks for the input

 

Just so everybody is on same page...You said you dropped the needle, then said you raised the clip..that's the same thing. I'm not being picky, but sometimes wording is everything. Also, your last post was first mention of a "hiccup". You first mentioned a surge then bike accelerates with no dead spots.
There are a couple of ways to do it, but I always tune carbs from bottom up. On stock CV carbs that's pilot jet, fuel screw, needle and main.
If you would indulge me...go over exactly what's it's doing again. Then exactly what those changes did please?
What size mains were in there before jet kit? What kinda humidity yall got there? I'm really surprised it wouldn't pull on top with needle clips in 3rd position from top.

 

I`ll try to clarify. When I say Hiccup, I mean the slight surge then dead then smooth out again.
It originally had dead spots at 2K, 5K and the hiccup just off the bottom of the throttle. Turns out, it had a Factory Jet kit installed. 3rd clip on the needle plus one washer, and Factory`s 138 main jets. But I had already torn open the DynoPro kit, so I swapped it in.
After my initial settings of: needle - second slot from top plus one washer, fuel out 1.5 turns, and DJ126 Main Jets. Then I tried the third slot plus one washer, which seemed to smooth out the hiccup but gave the bad dead spot at 5K and nothing over 10K. So then I moved the clip to the first slot plus one washer, pulls hard but the hiccup came back. So I played with the fuel, starting at 1.5 out, to 2 out (no real change), to 1 out (Worse). Bike temp also seemed to be an issue at this clip setting with a stuttering at cruise.
I live just outside Vancouver BC, humidity averages around 70%
hope this helps