Pulleys??

[2nd gen GSX]

I was wondering,since i was changing my belts, if swapping out the stock pulleys for some aftermarket ones would be a good idea. what are the benifits to the pulleys?

 

[SpoolinGSX]

While you are in there you should check out your stock pulley. It is a two piece design held together with rubber. If you notice any cracking in the rubber or chunks missing DO NOT reuse it! If it comes apart your valves will hit your pistons.
If you are going to change the pulley for an aftermarket one there are a few things to consider. First there is the obvious benefit of the pulley being lighter. Companies like Unorthodox Racing sells an underdrive crank pulley. This basically means the diameter is smaller, making it lighter and concentrating the mass closer to the center of the pulley as opposed to it being a larger diameter stock pulley. The underdrive effect is called such because it has a smaller circumference and therefore turns all of your accessories less with each revolution. So you will not be provided as much power to the accessories. If I remember the UR crank pulley is 15% underdrive or somewhere around there.
Second the stock pulley you will notice has holes drilled in it from the factory for balancing reasons. Putting a aftermarket pulley on will throw your crank balance out. How much? That is debatable considering the pulley is not that much mass to start out with. I think I recall my stock pulley being somewhere in the neighborhood of 2500g and the UR racing one being 500g. This new imbalance will wear out your main bearings faster as well as reduce your power output but as I said before the amount it is reduced may be very small depending on the the amount of imbalance.

 

[ballagsx]

i just wanted to point out that if your crank pully comes apart your pistons will not nessisarily hit your valves. it is verry possable though. what happens is the outer ring or the pully separates for the center and can smash the timeing belt housing and then can potentialy damage the timing belt.

just wanted to clarify how that works

 

[Morphius]

Second the stock pulley you will notice has holes drilled in it from the factory for balancing reasons. Putting a aftermarket pulley on will throw your crank balance out. How much? That is debatable considering the pulley is not that much mass to start out with. I think I recall my stock pulley being somewhere in the neighborhood of 2500g and the UR racing one being 500g. This new imbalance will wear out your main bearings faster as well as reduce your power output but as I said before the amount it is reduced may be very small depending on the the amount of imbalance.

The crank pulley is a harmonic dampner, not a harmonic balancer. Meaning, it's not balanced or counterweighted to offset any mass of the crank. The 4G63 is internally balanced.

Eliminating the Harmonic Dampner can have ill affects on your crank. It's there for a reason. If needed, buy another factory one. Buschur Racing sells an underdrive harmonic balancer. Expensive, but sell worth the money.

Here is a interesting statement by Buschur:
http://www.pacarsearch.com/stealth/buschur.htm