Putting an F2 Front end on an EX5

This page relates some of my experiences putting an early 90's Honda CBR600 F2 front end onto my EX500 chassis. It will be updated as appropriate, as the work is still in progress.

All of my F2 front ends arrived piecemeal with no axles or spacers. JJ of http://sportsmensracing.com sent me these drawings to fabricate my own spacers, including a dummy to replace the speedo head. He said I could share them.... You can view/print them one at a time, or all at once (see below). Click on the thumbnail to see the whole thing. Enjoy.

The AxleThe sleeveThe spacerthe speedo replacement
The Axle The Sleeve The Spacer The Speedo replacement

Click HERE to view the four .jpgs on one page (about 200Kb of graphics)

Click HERE to download the four Autocad Drawings in zipped format

As with any engineering project, there are numerous solutions. I'm presenting the one I used. This method inserts the EX5 steering stem into the F2 Triple clamps, so the standard EX5 steering head bearings are retained. This method was suggested to me by Andre and TJ, among others. Alternative solutions to mounting F2 forks in an EX frame may be as good or better, but I can't speak to them, having not yet tried.

This first cutting step required a little over 2 hours the first time, I'd expect it's more like 30 minutes now that I know what to expect. Start with one set each of F2 and EX5 triple clamps. The lower clamps are welded to the steering stems. Cut or grind this weld off. I used a cutoff wheel in my radial arm saw. It was easier than trying to get the dang things clamped onto my mill.Cut off one weld

I suggest cutting about 6mm off the bottom of the EX stem, and 8 or 9mm off the bottom of the F2 stem, then with the triple supported on something solid, knock the stem out of the clamp. I used an appropriate diameter socket with an extension on it. After a couple good whacks with a hammer, you should be able to see the seam between the stem and the clamp. If it's tenacious, grind off a little more of the weld metal. Don't worry about chopping through the outer edges of the lower EX triple clamp. You're going to throw it out when you're done. Once the EX stem is loose, it looks like this:EX triple with weld cut off

The hole in the top Honda clamp must be bored out to approx 28mm (from its stock 26mm diameter) to accomodate the top of the EX stem. I don't know any way to do this other than to use a boring head on a milling machine. The inner bore is almost perpendicular to the top and bottom faces, making it relatively easy to grip. I had to use some thin shims under one side to get the existing bore lined up with the boring head. After that, it was simple. The machinist who let me use his equipment for this said he estimated that boring one triple would be billed as a 30 minute job (machinist rates are about $45 per hour around here these days).

Cutting the welds offRun a weld bead around the inside of the lower triple, cut the top couple mm's off the top of the stem to allow the top-bolt to land flat on the top triple (I used my radial arm saw again), then assemble the whole thing. Whaa-Laaa! You got an F2 Front end!

JULY2000 NOTES: it is important to note that the top bearing nut on the stem (which rides below the upper triple clamp) is no longer jammed in place by the upper clamp! This means you have to fabricate a spacer or buy washers of the right stack height to do the job, otherwise your bearing preload nut will walk off, and your life will suck. Been there, done that. Didn't crash, but had a LOT of chatter in high-speed corners!

After opening my forks up for freshening, I determined that one of the springs was 1/4 inch shorter than the other...Watch those springs, folks! Word on the street is that 20 wt Bell-Ray oil gives better performance than the 15 wt with regard to chattering. I'll let you know after I try it. I do know that the 15 wt fresh oil was MUCH better than the mystery decade old oil that was in there when I first raced on it.
-------------a colorful spacer bar-----------

| TOP | Back to the EX page | HOME |

Last modified on 05JUN2000