Man, what an improvement.

S.E. 10.2:1 pistons.
Mild porting on heads, larger intake valve, new springs.
S.E. 204 cams.
Mikuni HSR42 carburetor.

Got it running last night and heat cycled it a few times.
It fired right up and sounded good.

But, I have a pretty bad flat spot in the 2-3,000 rpm range. if I roll on slowly, it runs great.
When I smack the throttle, it hesitates something terrible.

I bought the carb used, and it came setup with the following
Main- 180
Pilot- 27.5
Needle- 97-- clip #2
Accel pump nozzle - 50

So, after some research, I found that I was pretty fat for my motor.
Today I swapped in....
main- 162.5
pilot - tried a 22.5, no better, then went to 20
same needle - 97, and nozzle - 50

It seems better but still wont take quick throttle.

Raised the needle one groove to #3, same results.

It seems like it's still rich, as the exhaust is fumey, and kinda burns the eyes.

I rode it around for about 40 miles, runs great except for the hesitation.

got home and put my stock carb back on, which is setup with a CV Performance kit. Cant remember the numbers, but it always ran good on the 88".

Well, the CV carb runs great on the 95". Went for a short ride and it ran great.
I can feel that it doesn't perform like the mikuni though. (Rolling on, the mikuni felt like an animal).
The mikuni also makes the bike sound stronger.

so, I want to put it back on, but need it to run good.

Any suggestions ????

Also, Zippers back plate with open element K&N, Stock pipes with S.E. 2 slip ons.

 

Main 160 , pilot 20 and 70 accel, fuel screw about 1.5 turns out , and my bike runs strong, I too had that hesitation when opening the throttle full until I went with this combo

 

Always heard a mikuni was touchy to get just right. Once you do it will be awesome.

Big improvement over the 88 huh. I been pondering on doing a 95 to my 88 with a mild cam but no head work. But the way I been spanking the 96s lately with the 5 speed 88 I may leave it alone. I need a 103 to give me a good run before I make my mind up. I been pleased with the ole 88' it's a strong runner with a 5 speed

 

I'll try a 70 pump nozzle, but it already seem rich. I've tried opening up and closing the gap on the accel pump rod, but no change.

Thoroughly cleaned the carb. But, it was just recently on the sportster it came off from, and ran good on there.

I also sprayed the intake and everywhere to check for intake leaks, but it seems it's sealed up good there.

 

I thought my 88" was a pretty strong runner too, but it has nothing like the pull of this motor.
and i'm trying my best to keep it below 3,000 rpm. although I hit 4,000 a couple times today.
I don't ride with any 96" bikes, but my 88" will out run my buddies '14 street glide.
I should really wax him now.

 

If the heads are pre-06, depending on who did the porting and what the heads flow I doubt you'll see any differences as far as HP goes between the cv40 and the 42.. Maybe a little.. For sure the 42 is a better flowing carb but if the heads can't take it, the 42 ain't gonna help up top.. I've seen 204 create a bit of a dip depending on the exhaust.. Poor flowing intake make it worse.

Seeing as you seem to be running a stock ignition, it would surprise me that you don't get any ping.. I guess dumping enough fuel takes care if it..

 

Forgot about the ignition. I'm running a crane HI-4TC.
I haven't heard any pinging as of yet.

 

Thank you to the 3 out of 215 members that looked at this thread.

I figured out the problem.

I bought this carb used, and after much thought, realized that the accelerator pump plunger and spring is missing. nobody knows what happened to them.

so, waiting on some parts, but i'm assuming that will take care of the problem.