My brother has A yfz450 and he was having A similar problem.
What the the problem ended up being was the valves were out of adjustment.
In the owners manual it says that the valves should be checked for clearence every 25 to 30 hours of use.And the valve pads should be changed as well.Just A thought, good luck.
For A head unit(cd player)I highly recommend an Alpine, Its fully adjustable in any way with high, mid, and low crossovers built in.And it has three sets of pre-amp outputs(front,rear, and sub woofer.)
And its very reasonably priced. :thumbsup:
Adjust the pilot screws for idle, then at half throttle adjust those big flat head screws on the top of the tors.It is much easier once you get rid of tors.
The handling between A j-arm banshee and A a-arm banshee(stock of course)is roughly the same.
The j-arm banshee likes to eat up the upper bushings A little faster.
A-arm banshees are better because of all the aftermarket a-arms that are available.
They do make aftermarket j-arms and d-arms but they are not cheap, meaning they cost more than a-arms.