GPZ Intake and Exhaust Mods

JOHN SOLIDAY johnsoliday at
Sat May 2 12:00:44 PDT 2009

What is the source for the aluminum fan ?

> From: blackgpz at
> To: gpzlist at
> Subject: Re: GPZ Intake and Exhaust Mods
> Date: Sat, 2 May 2009 11:24:49 -0400
> Keith,
>      The ZRX1100 and GPZ motors are similar mechanically except for 
> camshafts and compression ratio. The GPZ is 11:1, the ZRX 10:1. The ZRX 
> camshafts are milder to keep cylinder pressure up with the lower compression 
> ratio. The GPZ camshafts are in between the ZRX's and the ZX11's in 
> performance.
>      There is no K&N OEM replacement filter for the GPZ.
>      Reed block-off plates are required for Stage 3 since some of the lines 
> for the KLEEN air system go to the airbox and you will be ditching the 
> airbox.
>      The reason for using an aluminum fan when replacing the stock exhaust 
> system with a header is the stock exhaust header pipes are double wall pipes 
> so there is not as much heat where they pass by the cooling fan. Aftermarket 
> header pipes are single wall and generate much more heat in this area, 
> increasing the chance of melting a plastic cooling fan. Another plus of the 
> aluminum fan is it's 6 blades in stead of 4 so it moves a lot more air when 
> needed.
> Steve in Western NY
> '96 GPZ1100
> '08 KLR 650
> '08 Tuono Factory
> "You Can't Fix Stupid", Ron White
> ----- Original Message ----- 
> From: "keith fraser" <fraskei at>
> To: "gpz list" <gpzlist at>
> Sent: Friday, May 01, 2009 8:50 PM
> Subject: GPZ Intake and Exhaust Mods
> I have been considering intake and exhaust options. I came across this page 
> on the muzzy site, , showing the 
> effects of different mods on a zrx 1100. It's my understanding the gpz and 
> zrx motors are very similar.
> There isn't much difference in power between the stage 1 and stage 3. I 
> would like to stay with the stage 1 but would like to replace the stock air 
> filter with a K&N. The air filter is tiny, only about 2/3rds the size of the 
> filter in my old Ninja. K&N doesn't list an air filter for the GPZ, anyone 
> know of a compatible K&N part #?
> If I did decide to go to a stage 3 would I need to buy the reed block off 
> plates? Is there anything else that would need to blocked off or disabled?
> Unless I find a really good price on a used exhaust system I will probably 
> buy the v&h supersport. It fits my budget and is the only black pipe I have 
> been able to find. Does anyone know of any dyno charts for the v&h pipe? Or 
> any other pipe and jetting combos?
> Also I have seen a couple sites recommending changing out the plastic 
> radiator fan for an aluminum aftermarket one, is it really necessary?
> Keith

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