Info for the Fat Axle Swap

[the_finch]

Starting note: alot of the info in this post is thanks to George (yamaha_george)

A little while back George (yamaha_george) posted some wheel bearing specs to use for converting from the 15mm stock front axle to beefier 20 and 25mm front axles.

As I understand it, the following would be needed for the fat front axle mod:
New front wheel bearings
New front wheel spacers (both the ones between the bearings and the ones between the fork/wheel/speedo sending unit)
Speedo sending unit
Front Axle
Fork legs bored to accept the new axle

First thing's first: why? With the fatter front axle is less prone to flex like the stock axle is, allowing both forks to work in tandem better and thus do their job better.

Here's what a little spare time can do for you....
According to the microfiche, a 1997 YZF 750 used a 20mm front axle. This helps, as the bearings used on this bike are the ones George researched for use on the 20mm axle conversion (6004-2RS). Another big help is that it appears that the bike uses a cable-driven speedometer, which means there should be a way to adapt the sending unit for use on the FZR600.
The only hiccup in using the whole front axle assembly is the front axle itself. It's designed for the upside-down fork assemblies that the YZF 750 uses, and it would be pretty tough to convert that particular axle. Solution? The 1997 Bandit 600 uses a 20mm rear axle of the same style as the FZR front, though it is safe to say it is alot longer. Cut it down and re-thread the end to the custom length needed and you're good to go (after getting your fork legs modified, of course).

I currently don't have the funds to pursue this mod myself, but thought I'd share some of the knowledge I'd collected in my research in case somebody else had the time/money to do the write-up on this.

[ragedigital]

That is really an ambitious mod.

I would find a way to replace the entire front system. The forks on my 05 GSXR are a leap beyond those that were on my FZR.

Since more and more bikes are using the USD forks, they are becoming increasing cheaper.... eBay Link

[the_finch]

That is really an ambitious mod.

I would find a way to replace the entire front system. The forks on my 05 GSXR are a leap beyond those that were on my FZR.

Since more and more bikes are using the USD forks, they are becoming increasing cheaper.... eBay Link

Thanks for the link and comment rage.

It probably would be lot easier to replace it with something newer, such as a newer FZR1000 USD front end or YZF600 USD front end. It would probably also be cheaper. I won't be doing this any time soon, as I replaced my front wheel bearings less than 1000 miles ago. And the only thing keeping me from just going to a different fork setup is the fact that I spent right at $200 on new racetech springs, cartridge emulators, and seals before I really knew what I was doing.

So currently, I don't really have the money for this mod, but I also have too much money tied up in parts for my forks to throw them away and go with something else. The only other person that this would be extremely helpful to would probably be CaptainCanuck, as he's building a FZR600 for a vintage class of racing, which keeps him from even swapping out the '89 swinger for a newer deltabox unit (a fat front axle would probably be considered cheating, but I won't say anything if he doesn't).

[95FZR600]

I suggest upgrading the entire front set up. There are a number of front fork set ups to use.

[yamaha_george]

hi,
well it is nice to know someone reads my scribblings :-}

The GSXR rear axle is cheap for sure, turning it to length is a cheap job, I would turn the bolt head end off (with a nice radius or chamfer for deep welding and use the threads as is and weld a drilled out nut on the "bald chamfered " end.

The cable tacho wheel end has plenty of room to be drilled out to size (yamaha aint stupid one size fits all (just a different boring tool for blah model :-}

wheel spacers again is a drill thro job (on a lathe is nice and easy but in a bench vice will do.

The only critical bit is the fork legs being drilled / bored square to axis, I have done this with a hand held drill machine with a suitable jig in place to keep it all square !!


Finch you may have invested in emulators & springs as I did and to me that is the best mod so far (at least until I put her thro her paces with the new rear GSXR6 shock & 3TJ s/arm, early tests look good but I have not been out thrashing yet {too busy giving the doctors a hard time })

[CaptainCanuck]

I agree, swapping the front end would be easier and better in the long run. If you want to recoup some of your costs on the emulator and springs I'm looking for some.