most Vstar bikes will rumble and pop and sputter when you compression brake with the throttle all the way closed
try cracking it open just a bit, the bike will not slow down as fast, but it will usually quiet the exhaust
I think there have been some threads about people modifying the hypercharger air intake so its not so agressively ramming air into the carbs. As Les mentioned the problem is it works great for max hp, ie drag racing or running on the track, it will really increase the HP by forcing air into the carbs, which allows them to be jetted for more fuel
air pressure (force hitting the front of the bike) is exponential with speed. When you go twice as fast there is 4 times as much wind resistance hitting you - the way the hypercharger is designed it takes advantage of that at high speeds, but when you slow down the airflow into the carbs is not a straight linear curve, so the jetting that is awesome at 90mph is rich at 45mph, and very rich at 30...
The main jets and PM ports control the fuel flow at different throttle openings, but its still difficult to get a bike with a hypercharger to run well when you are puttering thru town or down your street to your driveway.
Its a similar situation to putting a 'wild' cam in the engine - it will be great at 5000 rpm, but it will idle like your spark plug wires are falling off.
if you search you should be able to find threads by others who have modified their hypercharger to back off the ram-air effect a bit, both on this forum, and on other bikes / engines (on other websites).
Its a great looking intake - some people buy them just for the appearance. In fact there was a guy here a year or so back, who bought a bike that had one, and he could not get it to run well.
Turns out the previous owner was just building bikes for shows - he put a hypercharger on the bike, and impressive looking custom exhaust, but never bothered to change the jets in the carbs to match, they were still the factory OEM jets, because he never actually rode the motorcycle.
Last edited by KCW; 06-26-2019 at 09:26 PM.