below 4500 RPM Bog

[Each It]

I bought a 1985 VMax that came with 4 K&N filters on the carbs, no airbox. I Dyno'd the bike and was shocked at the 80 RWHP. If I go full throttle in any gear, below 4500 RPM, the bike breaks up, all the way through top end. If I go full throttle above 4500RPM in any gear, the bike runs great, no hesitation. Is the open airbox allowing too much air when the VBoost comes on? Should I disconnect the VBoost?

 

[maleko89]

What exhaust are you running? You're probably running way rich....and since it's bad from 4500 on up you'll need to make adjustments on the needle and main jets.

Let us know what your current settings are. Check size of mains, exhaust, stock vboost/open vboost, needles/clip position, altitude, location.

Mark
#1098

 

[Each It]

Running Kerker 4 into 2 into1 full exhaust.
It's only breaks up if I open throttle below 4500 RPM, then it carries thru to top end. If I open the throttle after 4500RPM, it runs fine. I think it's rich at lower RPMs during full throttle and floods the bike right thru to the top end.
How do I determine the difference between stock or open VBoost?
I will have to get back to you with the other info you asked for.
Thanks for your help
Phil

 

[4gasem]

I had a similar problem once and it was the plugs getting blown out... You may also want to check them as well...

I'm sure it's a carb issue but I was suprised by what I found! :surprise:

 

[maleko89]

Running Kerker 4 into 2 into1 full exhaust.
It's only breaks up if I open throttle below 4500 RPM, then it carries thru to top end. If I open the throttle after 4500RPM, it runs fine. I think it's rich at lower RPMs during full throttle and floods the bike right thru to the top end.
How do I determine the difference between stock or open VBoost?
I will have to get back to you with the other info you asked for.
Thanks for your help
Phil

I think you're right.

If you turn on the key, do you hear the vboost cycle? If so, you're stock. I was referring to some unplug the vboost in the open position so it's on all the time.

Mark
#1098