DOHC CB750 front end on a '74 CB360...will it work?

[hardline_42]

Hi everyone, this is my first post though I've been lurking for some time. I'm currently building a '74 CB 360 into a cafe racer. This is my first bike build, though I'm a tinkerer by nature and have a few car and truck builds under my belt. Since the bike is stripped down completely and wasn't running when I got it, I figured I'd do a complete rebuild and modernize it as much as possible. I'm starting with the front end and planned to swap in the larger 35mm front end off a CB750 and possibly run the dual disk setup. I know that the front end swap is fairly simple...with the SOHC year 750's. Unfortunately, I just picked up a set of forks and trees from an '81 CB750C before I read that critical little snippet of information. Will the '81 front end fit my CB360? What kind of wheel and brake options am I limited to with this front end (hoping to run spoke wheels)? Thanks in advance.

Brian

 

[hardline_42]

OK well, no responses so far. That's cool. I'll just do some thinking out loud. I know the DOHC CB750s had air-shocks up top. I'll probably just swap those out for regular closed fork caps, run Mike's XS 35mm cartridge emulators and the stock CB750 springs. Planning to match them up with some CB750 Progressive 11" shocks out back. Still not sure about my brake and wheel options. I believe that there was a DOHC model that had spoke wheels. I may have to wait 'til I get my forks in to see if I'll need a specific hub or if my CB360 hub can work. In the meantime, here are some pics:

When I got her:

As you can see, she's missing quite a bit. No kickstart lever, shifter, clutch or brake lever. Oh, and a nice little bird's nest in the carbs.

As she sits now:

Stripped down wearing a tank from an XS750 (mounting it will be interesting). I flipped the stock bars upside down to get an idea of how the bike's gonna sit while I wait for my clip-ons and CB750 front end. Also have an airtech tail on order.

Here's the required garage-riding shot:

Here I am, eyes closed in contemplation:

I welcome any comments, front-end related or not. Thanks for looking.

 

[hardline_42]

Well, here's an update for anyone who might be curious about my question. It turns out that the stem bearing sizes are as follows:

'81 CB750C:
Upper - 26x47x15
Lower - 30x55x17

'74 CB360
Upper - 26x48.5x15.2
Lower - 30x50x14.4

From what I've been able to glean from this info, both stem bearings have the same diameter. So the stem from the DOHC 750 "should" fit the 360 frame, provided it's the same length as the 360 stem or slightly longer, in which case I can fab a spacer to take up the extra length. If not, I'll have to swap steering stems.

Now, I'll have to wait and see if the hub spacing will accomodate my 360 hub. If so, I' have a nice CBR900RR brake swap planned.

 

[hardline_42]

Well, unfortunately I've hit a snag with the front end swap. The fork tubes and lowers from the CB750C are too long to work for my application.

I had to slide the forks up about 4" through the trees just to get them to match the stock height of the CB360 forks, nevermind that I had planned to lower them about an inch from stock.

This in and of itself wouldn't have been a deal-breaker (even though my front end looked like a giraffe's head) except that the fork lowers on the CB750C are a good deal taller than the CB360 lowers, reducing my front suspension travel to an unrideable level. I could bottom them out just by pushing down on them with my upper body weight.

So, I've given up on the DOHC forks, even though the leading-axle stup would've provided a little more trail and the air-forks were a nice touch. I've decided to sell them for anyone who's interested.

Instead, I went back to my original plan and picked up a set from an SOHC CB750 off eBay complete with a dual disc setup: calipers, discs and hub. Looks good to me (the top tree isn't pictured but is included). I'll have to wait 'til it arrives but they already look a good deal shorter than the DOHC set -