Gents,
I am new to your forum, but a frequent contributor to several others on Ducati. I have a 1990 750 Sport. Actually, I have 2 of them.
I am building up my 2nd one as a custom/hotrod. The swingarm was not the original, and it was destroyed by the sprocket bolts, and a misplaced spacer. In an odd reversal of roles, I got a steel F1 swing arm that I will be bolting on. Same pivot pin, and shock mount. I picked up a few spare swingarm plates and adjusters. (seems the appetite for the Verlicchi swingarm on this forum has made it hard to find one)

I am planning on using a rear wheel from a Sport Classic that has a 25mm axle. Width at the axle seem to work just fine, and tire clearance seems to be OK, but tight.

So, Here's the question:
- Has anyone ever put a 25mm axle into a round steel tube swingarm before? Seems easy enough as the odd spacers in the swing arm are 25mm rounds, and the flats are only 1.0mm each.
- Do you see any negative side affects of boring out the swingarm side plates, adjuster slider, and swingarm to accomodate the 25mm axle, and forgo the odd spacers in the swing arm? Its only a millimeter on each side.

Thanks for any insights and thoughts.

Cheers, Phil

Hi Phil, I guess my thoughts would be to change the bearing in the wheel (if that is possible) to accomodate the right size for the axle you are using. Secondly, what size is the rim and tire combo you are using? I would be very surprised if it fit the steel swingarm. Lou

Their are several problems in changing the the bearings in a wheel.
First is that the width of the bearing changes when the aspect ratio changes. So a bearing that has (I think) a 47mm outer bore and a 17mm inner bore, has a few more millimeters added to the width compared to the 25mm ID bearing. The taller bearing has bigger balls, and hence, wider races. So the whole wheel width stackup gets wider, and affects the whole assembly. Boring a hub is not an easy task, nor is changing the mating parts such as the caliper hanger and sprocket carrier to get all of those parts to align and work properly together again. It all can be done, but I'm just looking at the simplest route.

As I am seeing it right now, one 25mm end mill will open up the 4 side plates, the 2 sliders, and the siwingarm. The cut will only be 2mm, one on each side. Actually, the slot in the swingarm is almost 25mm already, so the cut will be about 1mm total.

What is the purpose of those spacers in the swing arm that are 25mm outside and 17mm inside and have two flats on them? Do they simply keep the side adjuster plates in place when the wheel is off? Seems like a lot of steel not doing much. Wouldn't an axle the full diameter be stiffer, and lighter? Am I missing something? Seems like a poor design based on the fashion of a 17mm axle of the time.

Cheers,
Phil

Not to mention that the Sport's vertical exhaust header is pointing the wrong way for the F1 Swing arm.
Bill

Hello Phil,

I just fitted 696 monster rims to a TT2 rep that was a 95 SS engine and swingarm.
The axle for the SS is 17mm but the 696 is 25mm.
I couldn't get bearings to fit the rim and 17mm axle so I made steel bushes to reduce the bearing ID to fit the 17mm axle.
And made a new bearing spacer to suit the bushs flange.

Hope this helps,

Graeme

Hi Graeme
Your bike looks fantastic, love the black wheels

Hey Graeme your bike is a beauty! Phil you are correct about the bearing size increase, I guess I thought as Graeme that a combination of bearing and bushing might do the job, but I guess you would like to use the larger axle and avoid all the other mods. Let us know how you do, the ingenuity on this Forum is top notch. Best of luck. Lou

Lou,
Thanks for the encouragement. I'll take some photos and post them as I progress.
Cheers, Phil

Uh,Bill [Pantah Good] Kinda beat me to what I was going to say. The cross brace for the swingarm is right where the vert. exhaust needs to be unless you reroute it.

Yeah, thanks, saw that coming. I'm making a whole new exhaust system for the build, and will run the rear pipe on the other side of the cross brace. I'm making some high pipes to mimic the '72 Imola . Routing for the rear cylinder gets a bit convoluted, to say the least. Stay tuned.

Cheers, Phil