I need some guidance to make sure I'm on the right path here. The bike has the stock keihin CV carb. Since I bought it, the bike hits a wall at 4500 RPM, then comes back to life a few hundred RPM later. I replaced the drag pipes with a 2 into 1, replaced the jets (had 45/170) with 46/180, shimmed the stock needle, drilled out the emissions plug and have the screw at 3 turns. I also chopped up a stock airbox and put in a K&N (HD-1390) filter.

I expected the pipes to fix the problem, but there has been no change. Had a friend ride behind me the other night and gave it a blast and he mentioned that there was an orange glow when I hit 4500 RPM (exhaust note changes, it's sort of violent). The current thought is that the main is coming on too late (right around that time). The question is, how do I fix it? As I understand it, changing the needle may help. Should i go with the N65 or the CVP velocity needle? Would a lighter slide spring also help? Basically, I need the slide to move up faster, right?

TIA.

 

I think the most recommended idle jet for a CV is a 48.

 

Are you saying a few hundred rpm later as in higher or just a reference to amount of time it starts running ok? Is motor stock? Was carb modified prior to you running it?Sounds like a problem in ignition system.

 

It is a stock (as far as I know) motor. There was a marred up 45 slow jet in it when I first opened up, so somebody had been in it. However, they hadn't drilled out the emissions plug on the mixture screw.

What I mean is that the bike pulls nicely, then at 4500 RPM WAM!, face on the handle bars.. then by 4700 RPM, we're pulling hard again.

 

Bump. Anybody have any ideas?

 

Same issue here and it's new. Except mine doesn't turn back on at 4700. Did you figure it out?

 

you are in a high humid area and with out the use of a performance kit - you have too much jet and the needle is in the wrong spot being rich < too tall in the clip and OR shimmed to high

kinsler kits < made in japan and the only one i use in my shop 20 years now, when your done installing it most carbs have a 160 main and a 42 low speed and that is with a cam and a compression increase using thinner gaskets -- good fuel mileage - starts in the North east very well late fall - real good plug color - great throttle responce - its what we do in a shop so you dont wash out the piston rings with fuel trying to make a motor that has good VE run on big jets - that is for the guys who ported the heads so they never work correct again - just my take been doing it 2 weeks now

 

John I bought a cvp kit to rejet. It had a dynojet emulsion and 180 main when it started doing this. It now had cvp emulsion and 180 main and 45 pilot with the cvp needle and no shims. K&N filter stock airbox. Your saying it's too rich?

 

I did the CVP tuner's kit with their spring, CVP mid range needle, 45 pilot, 170 main with CVP emulsion. Seems like she runs well with decent mileage.

 

If I'm not mistaken shimming the needle richens it up across the board and doesn't change when the main comes in. I'd pickup the N65 needle as a start. My Fatboy is stock except for cv mods Sportster needle, 45/175 jetting with a hypercharger. I also run Longshots with no baffles. Not optimal but I like it.

Side note I believe the main comes in around 3500k.