6 replies to this topic
  • BadhabitMX

Posted April 13, 2007 - 08:16 AM


Hey guys,
I am a college student, shopping for engines my school's FSAE team. FSAE is an international competition where students build and compete with their own formula style autocrosser. To get to the point, this year I am leading the engine team. Because of my previous knowledge with the WR/YZ line, I want to use one of these. It will most likely be highly modified (bored, stroked, ported, high compression, etc). My question is in regards to the transmission; I vaguely remember the WR having a wide ratio transmission, as opposed to the YZF's close ratio. Is this true/still true? If so, what years does that apply for? Also, if anyone knows the specs of the YFZ's tranny, that would be great.

Thank you!

  • msgbean

Posted April 13, 2007 - 08:39 AM


All WR's have the wide ratio transmission. That's what WR stands for. If you want to know the exact specs for the YZ or WR tranny I would need to know the year of the engine you have in mind. The WR's have always had a five speed but some of the YZs have a four speed.

  • ez__rider

Posted April 13, 2007 - 09:56 AM


The motors are indeed what makes these such sweet bikes, but is it really best for your application? very different from the 600cc F4i engines and the like... then again, you could potentially end up with a much lighter design.
just my 2 cents. good luck in whatever you decide!

if this is really the engine you choose, I think you found the right place!

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  • BadhabitMX

Posted April 13, 2007 - 12:13 PM


Ah, now I feel ignorant... I knew that WR stood for wide ratio, or at least I used to. Thanks!

I believe it is best for us. Previously, we used a Yamaha R6 motor. It was what we started with, and it stuck. However, we are forced to run a 20mm restrictor. That limits the R6 to around 70 horsepower, I believe. Our displacement limit is 610cc's. I came in, a new member this year, with a good amount of motocross experience. The four cylinder seemed inappropriate for a small race car. It is simply too heavy, in my opinion. I currently ride a YZ144, and previously owned a YZ265F. For the past couple years, teams have done well with single cylinder motors. With modification, and fuel injection, RMIT was getting 60 whp out of a WR450 last year. The weight reduction is around 65-70 pounds just out of the motor, not to mention the lighter drivetrain, smaller fuel tank, smaller overall frame, smaller exhaust, etc. The electrical system is also greatly simplified. The goal for this single cylinder car is something between 400-450 pounds. We are just starting organization for the 2007/2008 year, so if you guys have any suggestions, I am very open to them.

Thanks again!

  • goodluckmonkey

Posted April 13, 2007 - 03:00 PM


Why not use the YZ? surely the longer 1st gear, and closer top would be beneficial in a race car???

Only thing that's really gonna tie you, is if you bump-start the car, or need to run e-start. Then the choice is already made for you.

  • BadhabitMX

Posted April 14, 2007 - 03:26 AM


E-start is a requirement. The driver has to be able to start the car from the cockpit with no additional assistance, on flat ground. We have also found that the fewer shifts, the better; the goal is to only use 2-3 gears. I was not aware that the YZ has a taller first; thats interesting, but probably a moot point because of the required starting procedure.

  • msgbean

Posted April 14, 2007 - 06:18 AM


Here you can compare the ratios yourself.

______________________07 YZ_________07 WR
Gear Ratio - 1st Gear 27/14 (1.929) 29/12 (2.417)

Gear Ratio - 2nd Gear 23/15 (1.533) 26/15 (1.733)

Gear Ratio - 3rd Gear 23/18 (1.278) 21/16 (1.313)

Gear Ratio - 4th Gear 24/22 (1.091) 21/20 (1.050)

Gear Ratio - 5th Gear 20/21 (0.952) 21/25 (0.840)


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