Thread: need help 2003 gpr1300
07-26-2008, 07:41 PM #1
need help 2003 gpr1300
need some info!
i have to change my top end in gpr1300
1.can i use :
3 - Brand new 90mm Wisecos (hopatcongGPR Big Bore Kits)
3 - GPR 66E cylinders - Welded boost and bored to the 90mm pistons + plating clearance ????
2. i'm looking for big''kick'' from low RPM , no need top speed
any ideas ?
thank you for all info
07-26-2008, 07:47 PM #2
There is work to do to finish, you will need more than just the hardware. if you are serious, I would contact Lowell Horning to see what it would take to complete the job. http://www.2-stroke-porting.com/
07-26-2008, 07:54 PM #3
07-26-2008, 08:00 PM #4
I have two skis that are both ported the bigger you go the more involved it becomes. If you have good skills take on the project. You can have your damaged top end redone and ported for less and have a screamer. I don't want to take sales away from anybody, I just don't like seeing what happens to people when they get too far ahead of themselves or their skill set. Lowell is a great source for info and work I suggest you send him an email with your needs and questions he is honest and top notch.
07-26-2008, 08:08 PM #5
not a simple question to answer
the size, position and height of the port openings needs to be correct in order to maximize the HP of the motor
when the cylinders are bored to 90 mm it changes the heights of the ports
when you bore out the cylinders you expand the displacement of the motor which changes the requirements for the ports
this is complicated stuff, engine builders use software to help them optimize the design of the port opening
07-26-2008, 08:15 PM #6
07-26-2008, 08:39 PM #7
Yamaha makes 4 different cylinders
60T power valve (2003 - 2004 gp1300R)
60T non power valve (2005 - 2008 gp1300r)
all 4 cylinder types start with different porting
so the question is, which of the above cylinder types should you start with if you want to bore the cylinder out to use a 90 mm piston?
actually it is a 2 part question, because you also have to decide if you want to use a custom stroked crankshaft or not? (approx cost $1,000) by stroking the crankshaft the engine builder has more flexibility in how he designs the motor
here is one example of a motor built using these pistons
07-26-2008, 08:48 PM #8
07-26-2008, 09:17 PM #9
the other thing that should be mentioned is I think all of the motors that have been built with 90 mm pistons use the GP1200R electrics (CDI, etc) and use carbs (this is because the 1300 EFI set-up cannot provide enough fuel)
so to use 90 mm pistons you would have to also use gp1200r fuel tank, carbs, wiring harness, CDI, stator, flywheel
07-27-2008, 12:40 PM #10
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what about running larger injectors ?
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