489cc screamer build

[Kurlon]

I've just picked up an FZR 400 project to use as a means of getting back into racing. My goal is to make a short stroke 489cc screamer by shoehorning an FZR 400 crank (once I FIND one) into a YZF600, retaining the 600's top end and modifying as needed to make the two live together happily. Seems everyone is going bigger these days (660s? Cool!) but race restrictions cap me at 500cc.

Has anyone traveled down this road already and care to share any pointers? So far digging around it seems there is one crank seal that may give me trouble, and I'll have to sort something out with the ignition as the rotor/trigger setups aren't directly swappable between the two mills? If I can build up the YZF head so it'll survive trips to 14k I'd prefer to use the 400's ignition/CDI.

Anyone know where there is a stash of 400 cranks hidden?

[sweekster]

This is the first i've heard of such a thing. I quite like it actually. But...

[blensen]

Don't take it as fact, but I believe that the stock yzf600 revs to right around 13k. With a shorter stroke, I'd think hitting the 400's 14k redline should be no problem. Should be a wicked little motor by the time you're done.

[zero9243]

This is the first i've heard of such a thing. I quite like it actually. But...

As long as it has polished lips, duane will like it

[Kurlon]

This is the first i've heard of such a thing. I quite like it actually. But...

Heh, not much to see at the moment.

https://picasaweb.google.com/lh/photo/5 ... directlink

For some reason I thought YZF600s had a much lower redline. If they're showing 13k stock the head is in much better shape than I thought, I can tune for a 13k redline and be happy I think. Next debate is rod choice, if I retain the YZF rods I have to deck the YZF cylinder about 6mm, and a laaaaazy 2.8:1 rod to stroke ratio. 01-05 R6 rods have the right big and lil end dimensions but are 91.5mm compared to 115mm long. That means taking 28mm out of the cylinder (dunno if that's doable...) and a much more sporting 2.3:1 rod ratio.

A custom billet cylinder would solve that issue, those are cheap, right?

[Kurlon]

The more I compare part fiches and pics along with digging around online the more I seem I'm going to need from an FZR400 motor to complete the swap. Clutch primary gears are different sizes so I'll need to resolve that. Flywheel tapers are apparently different... almost looks easier to start with an FZR400 and swap top ends rather than start with the YZF600 as a base.

[Kurlon]

So, no new pics yet, but lots of build news. To get around the YZF/FZR crank compatibility issue, I bought a former race FZR 400 RR SP (3TJ) complete with a viable 400 bottom end. Speedwerks has done a few of these scream builds over the years so rather than learn as I go and possibly guess wrong on some critical detail, I'm letting them handle the motor build.

My current task is trying to figure out if a 99 R6 wheel set can be adapted to the 3TJ forks and swingarm without 'reinventing the wheel'. As an added bonus I have neither the wheels or my chassis on hand to get measurements from. Thats right, I get to mock it up using nothing but the internet for data.

[pefrey]

Where did you find the RRSP?

[Kurlon]

Where did you find the RRSP?

Pure dumb luck. It was posted in the fzrarchives classified section the day I decided to take a random stroll through. Former WERA race machine, one of 3 3TJs that Speedwerks imported for people over the years.

[SouthendChris]

Regarding the R6 wheel in the 3TJ this is something I am looking into myself. The steering head bearings on the 1990 FZR400 and upto 2007 are the same according to http://www.allballsracing.com/index.php/forkconvertion

Whether the 1990 'FZR400' they are refering to means the Jap 3TJ or UK 4DX is open to question. It does mean that an R6 front end could be grafted on, or even early R1front end using R6 yokes (4XV?) - which would be nice

Chris