1975 RD350B

[85RZwade]

Awesome, Rodney! I have that site bookmarked already. I'm still looking at options; pretty sure I want spokes, and I was thinking on the drive home tonight about the CB550K wheels I have. Single disc front and drum out back, and I would have them laced to some nice 18" hoops.
I perhaps foolishly sold my OEM RD hubs (as you know) thinking...I don't remember what I was thinking except that I wasn't going to use them. I don't want to build a 'tracker, but I was also thinking about this tonight:



Already has a disc but it's 19" and I'd have to come up with a rear to match, which could be tricky. Maybe I'll go look at the 550 wheels before bed...

[85RZwade]

And then, I had an epiphany! Maybe it was a minor stroke; I don't know. Anyway, that KZ650 front wheel is a 19x2.15, single disc with threaded holes for another disc (sprocket?). I realized that there's a KZ1000 in the barn with a similar front wheel: 19x1.85 with two discs. I quickly slipped the Motolana swingarm in place, went through an act of Congress to get the wheel off the 650, and voila!:









That last one is all artsy, right? So a 19" 110-series wheel and tire fits just fine all the way forward in the swingarm. With the narrower KZ1000 front wheel up front, I'd have matching 7-spoke cast wheels of slightly wider-than-stock widths running tubeless tires...sweet!

[85RZwade]

But wait! Remember, I said I wanted wire spokes, right? In front of the KZ1000 is a '78 CB550K with nothing better to do than donate it's wheels...:



19x1.85 with 40 spokes



18x1.85, also 40 spokes. So I could also have wire spoked wheels with a single disc in front and a drum in the rear, but there'd be that weird-Alice 19-inch front, with 40 freakin' spokes!

[85RZwade]

I'm not done! Back to the boneyard...remember this stray that followed me home?



'72 Suzuki TC125, 18xwho cares rear wheel, drum brake, cush drive sprocket and 36 spokes:






What's significant about 36 spokes, you ask? Something else has 36, but you knew that:



The RD rear wheel is 18x1.85, and although I sold the hub, I still have the rim. Bear with me, now: CB550 front hub laced to CB550 18x1.85 rear rim and TC125 rear hub laced to RD350 18x1.85 rear rim. I'd have two 18" wire-spoked wheels, a disc in front and a drum out back, just as Yamaha intended. Is a rear hub from a 125 adequate for a breathed-on 350 twin? No, really, I'm asking...

[Jspooner]

Do you need some 350 hubs?

[pidjones]

One must be careful when cross-breeding species that you don't start something that can't be stopped. The little 125 hub looks a bit small for this, although it IS just a rear. Would have to work beyond design and be watched for overheating. Maybe pair it with dual front disks? How was the 125 regarded back in the day for its rear braking ability?

[85RZwade]

Joe: maybe. I'm still blatantly violating your signature line! Some would call it "weighing my options". Since I'm not using RD forks or an RD swingarm, I don't feel that RD hubs are necessary.
pidjones: I have reservations about the size of that Suzuki hub as well, and I don't know the history of the TC. I've spent most of my mad money on carburetors, ignition, swingarm, engine work for the RD and engine parts and work for the LC. Back to looking at what I have on hand. More on this later.

[Jspooner]

Joe: maybe. I'm still blatantly violating your signature line! Some would call it "weighing my options". Since I'm not using RD forks or an RD swingarm, I don't feel that RD hubs are necessary.

Not to tell you what to do because the choice is entirely yours but I'd use RD stuff just to simplify it. Use RD400 forks with Racetech emulators and springs and you'll have a pretty nice front end.

[pdxjim]

^ He's right you know.

Modern running gear, maybe, but no way would I be bolting 70's Kwak and Honda junk on my RD.

I guess the KZ 19's would be appropriate for a "street tracker" style build, but if you're going to go to the trouble of lacing wheels, seems like sourcing proper RD350B hubs would be worth the effort

[zedixe13]

XS360 used basically the same rear wheel as the RD350

[85RZwade]

And then, I realized that the GSX-R axle is 25mm, almost as big as the O.D. of RD wheel bearings. Forget all that earlier wheel rambling; I'd have to have a new axle made or use needle bearings...and I might yet talk to the local machine shop about an axle. In the meantime, I allowed myself to look at the Cognito Moto site and I might be in big trouble. Of course, they have already solved my problem with a custom spoked hub, bearings, spacers, spokes and rim of choice for just $900. The budget-minded among us can opt for the bare hub at only $400, and pick up the spacers, bearings, etc. ala carte. Gulp.

https://cognitomoto.com/collections/gsx-r-conversion/products/bolt-on-laced-wheel-for-gsx-r-fork-1996-2017-complete?variant=2959129182248

https://cognitomoto.com/collections/gsx-r-conversion/products/1996-2000-gsx-r600-gsx-r750-srad-hub-bolt-on-conversion-laced-wheel?variant=11056925377

[rodneya]

Might be easier to make a sleeve for the gsxr wheel so you can use the smaller axle.

I got lucky and found a cognito moto setup with a matching rear wheel for sale on craigslist, conveniently at the exact same time somebody else listed a GSXR front end.

[bostontrackrat]

I REALLY like what you're doing with this project.  I'm really eager to see how that swingarm performs and holds up, and if it's worth getting.   

[85RZwade]

Me, too! No buyer's remorse yet; it really is a nice piece in person. Would it be too much black to have the fork sliders anodized to match the swingarm  or 

[bostontrackrat]

I guess that depends what color you're going to paint the tank, and if you're going for an overall "dark" aesthetic. If you arent, I might leave them aluminum to brighten the bike up a bit.