Topic: 1982 Honda CB650SC - Triple Tree Clamp swaps

[papi_sosaa]

I'm currently in the process of pulling apart the front end of my Nighthawk and decided that I would like to swap out the stock triple tree clamp. I'm still compiling information on what triple tree clamps will work with the 650SC frame and I'm just looking for any insight and or measurements.

What I know so far is that the 1982 Honda CB650SC has:
- 37mm forks
- 192mm axle spacing
- Air assisted forks
- Progressive springs?


Option 1:

According to this post (reply #38), the '81-82 CB900C has near identical measurements.
http://forums.sohc4.net/index.php/topic,139630.25.html

Would the 900F's triple tree clamp assembly be direct bolt-on or will I need to get spacers or even a different stem for it to sit correctly in the CB650SC frame?



Option 2:

The '81-82 CB750F triple trees also use 37mm forks so would this work? Reply #2 in this post mentions the 750F triple tree clamp but not much else.
http://forums.sohc4.net/index.php/topic,17486.msg186612.html#msg186612

Is the fork spacing on the 750F triple tree clamps the same as the 650SC?

I'm going for a minimalistic approach, the 750F bottom triple tree clamp would allow me to use this top clamp alongside some clip-on bars to meet that goal:
https://cognitomoto.com/products/billet-top-triple-clamp-cb750f-1980?variant=3855303671848

Also, can the air-assist on the 650SC forks be capped off or is that something that is functional for the operation of these forks? I assume I'd have to get 750F forks if I wanted to delete the air-assist function/feature.

[fizzlebottom]

The air-assist feature of the forks just allows for an adjustable preload. Some folks have capped them off while putting an appropriate diameter 1" or so spacer at the top of each.

Regarding swapping the triple trees, let's talk about why you're doing that. It isn't bad in any way, but depending on your overall goal, you may end up doing more work than necessary if there's another way to reach the goal. So what are you trying to accomplish?

Tourmax over at this thread (http://forums.sohc4.net/index.php/topic,189755.0.html) has done a seemingly insane amount of work, some of which includes an entirely different front end. Consider looking at what he's done for inspiration if you are steadfast about a different front end.

[papi_sosaa]

Regarding swapping the triple trees, let's talk about why you're doing that. It isn't bad in any way, but depending on your overall goal, you may end up doing more work than necessary if there's another way to reach the goal. So what are you trying to accomplish?

I like the top clamps from Cognito Moto because of the clean “minimal” look. Would pair nicely with some clip-on handlebars. If the fork spacing between a 750F tree and 650SC tree is the same then I “should” be able to just get the top tree off their site and call it a day. I say should because I can’t find the measurements to compare.

[fizzlebottom]

Few folks on the HondaCB650 forums have apparently had a similar discussion: http://www.hondacb650.com/viewtopic.php?t=9955

Give it a read. I really can't tell what the conclusion is from 8 years ago. If I can get an accurate measurement on mine, I'll see what the spacing is between forks and let you know. The only part that I can really find on the '82 CB650SC front end that's shared across other bikes is the axle shaft itself: https://www.partzilla.com/product/honda/44301-461-770?ref=2eda1fc03d8abaae71da973ebb0da455381bff31

It doesn't say anything definitive though. I'll try to measure fork spacing later today.

[kerryb]

If you intend to use clipon bars, why change the top triple.?  You wouldn't have to remove the bar clamps because they aren't visible.  I just raised the tubes through the trees to make a place for the clipons to attach.

[papi_sosaa]

I just raised the tubes through the trees to make a place for the clipons to attach.

I noticed that you and Hutch mounted your clip-on's above the triple tree. What made you install them there rather than below the triple tree? Would the clip-on's be too low if you did that or would it almost hit the tank/put you at an awkward angle at full lock?

[kerryb]

Form and function played a role here...I raised the tubes througb the triples to lower the front end.  This bike had cruiser/chopper styling with longer forks from the factory.  I had a couple of designs to put the bars over/around  the tubes, but since I set out to build a cafe style bike, clipons were appropriate AND covered up the exposed tube tops.  If you're curious about other details & compromises, here's the build thread;  http://forums.sohc4.net/index.php/topic,174985.0.html

[kerryb]

You might want to look at my build thread, seat houses custom airbox, electric are in other places.  Seat hump has fuse box &regulator.  Battery box behind tranny area.  ‘82cb650sc project at www.cb650forums.com