Jared's 1982 CM450C Cafe Project

jaredc7

Get busy living.
Hey everyone! After pouring over countless posts from you all (extremely helpful) and getting a few books to learn on my own, I've finally started a cafe rebuild for my motorcycle. Just started to tear into it a couple weeks ago, and trying to only focus on one problem at a time. I'me sure you all know how overwhelming it can be trying to do multiple things at once! Here is what I'm working with...

1982 Honda CM450C
Purchased April 2013, and rode it most of the summer
About 22k miles

Goals for Cafe Rebuild
- Single swing arm conversion
- Monoshock conversion
- Old styling with modern performance parts

I'm already into a couple issues and expect some custom fabrication. I'm looking forward to hearing a variety of thoughts and ideas from this forum!
 

jaredc7

Get busy living.
I got in the single swing arm from a 1990 Honda Hawk NT650. It was by far the best option for a single swing arm for my 450CC bike. Here are some details...

Honda CM450C
1 - Swing arm pivot diameter: 14mm
2 - Distance between inside edges of swing arm (or width of swing arm pivot at frame): 5 and 5/16" (roughly)
3 - Distance between pivot rod CL and rear axle CL: 20"

Honda Hawk NT650
1 - Swing arm pivot diameter: 15mm
2 - Distance between inside edges of swing arm: 5-3/8"
3 - Distance between pivot rod CL and rear axle CL: 21-3/8"

Some other swing arms I considered...
- VFR800 Interceptor - 20mm, 6-7/8" wide (10.75" wide at outside edges)
- VFR750 Interceptor - 20mm, 247mm wide, 570mm long
- Variety of Ducati and Triumph brands... pretty much ALL other single swing arms have a 20mm diamter pivot shaft.

Since the Honda Hawk NT650 is the closest in dimesions, as well as overall bike size, the choice was easy. Now to get the damn thing to fit!!!
 

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jaredc7

Get busy living.
Here's my thoughts to get this swing arm to work. Any thoughts here would be greatly appreciated.

- Remove rear tube section of frame so left side of swing arm is clear to move.
- Cut out existing pivot rod housing from CM450 frame
- Cut out pivot rod housing from a Hawk NT650
- Weld in NT650 pivot rod housing into CM450 frame, moving the centerline about 3/4" farther to the rear so swing arm clears transmission case.

Questions!!!
- Will I need some additional reinforcement here when welding in the new pivot rod housing?
- Should I get a monoshock and fab/install the top mount where it should go to accommodate that shock? - OR - Weld in the monoshock top mount where it "should" be, for structural integrity, and size the monoshock for that specific application?
 

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1969Honda

Member
Do you have the rear wheel and sprocket carrier in hand yet? If not you'll want that in hand first to see where your sprockets line up and what will be required to center the wheel and line it up with the front. Once you get those figured out post up some pics with them installed and I'm sure some of the more talented and experienced builders (teazer, bradj, sonreir, crazypj, von yinzer, etc...) on here will offer up their 2 cents
 

jaredc7

Get busy living.
I do not have a rear wheel and sprocket carrier. I am looking at some different wheels that will work with the Hawk NT650, including the Interceptor VFR 750 and 800. Not really a big fan of the stock NT650 wheels. The VFR models have the same design of single swing arm.

One thing I realized is that the Hawk's frame mounts to the outside of the single swing arm, so there is no "pivot housing" I can steal from the Hawk. For my 1982 CM450, the swing arm will have to straddle the frame (as you can see in the pics). Very different! It may take some extra work to line up the front and rear, but since I will be modifying my existing swing arm pivot anyways (for clearance with the right side of the transmission case), I'll be able to move it anywhere I need to. Not to say it won't take some finesse!
 

jaredc7

Get busy living.
Custom Fab: monoshock top mount

Here are a couple CONCEPT drawings showing some options for the custom monoshock top mount. Let me know what you think, or if there are other/better options out there!

I will be using the rear shock off of a 2009 CBR600 RR. From all the people I've talked too, this seemed to be the best and most economical approach... Unless someone has a spare YSS, Wilber, or Ohlins shock lying around??? hahaha. I bought the CBR600 RR shock for $50 on eBay.
 

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jaredc7

Get busy living.
I know the orientation/perspective is off on these, but they are just concept drawings...

The yellow lines are welds visible from that particular persepective, and the red lines are welds behind the material.

Maybe option 2 could be bolted on instead of welded? Just exploring options, I think I would prefer welds here.

Let me know what you think!

Thanks,
Jared
 

1969Honda

Member
The rvf400 rears can be put on that swing arm with the corresponding eccentric and axle set up and a little modding to the brake system mounts if you want an 18x4.5 rear wheel. You might even be able to go for the NSR250R single nut rear wheels as well, not sure just some of the different routes I've been researching. In a couple months I'll be back home and have access to all of the eccentric and wheel dimension for SSSAs that I have been collecting for awhile. If you need further measurements and fitments for wheels and the swing arm check out www.customfighters.com, there's tons of swap information for the NT650/VFR swing arms.
 

cxman

Active Member
DTT SUPPORTER
you are about to put a considerable twisting force onto a stamped sheet metal frame member

in order to support the single sided swing arm

the whole center section will need to be strengthened and re=enforced as well as i might suggest

solid butt welded as it is only spot welded together
 

jaredc7

Get busy living.
Thank you CXMAN and 1969 Honda, both very good points! I am looking into a larger housing for the swing arm pivot rod (steel tube 15mm ID, and 3/16" wall), as well as strengthening the steel around that housing. I'm also having a friend do a stress analysis and engineering design on the rear shock top mount. Hoping to optimize that connection.

One thing I am having trouble with is my research on the front fork swap...

I've looked up the extensive list of front and rear axle diameters, steering stem bearings, etc. but cannot find bikes listed that are newer than 15 years old! I'm looking for a newer set of used forks that would work with VFR wheels (20mm diam axle). Are there any newer bikes that have a 20mm front axle diameter? If not, couldn't I just get bearings from AllBalls with the same ID (20mm) and a larger OD to accommodate the larger diameter axle size on the forks?

FYI... I assume to be pretty constrained to VFR wheels on my cafe rebuild because I am using the NT650 Hawk single swing arm and need the offset rear wheel. I would use the Hawk wheels but they look like crap. Also, from the research I've done, a conversion to Ducati or Triumph offset wheels seems far too involved. Maybe I'm mistaken about the ducati and triumph wheels?

Thanks!
Jared
 

swan

Kickstart, shift on right, drum brakes and spokes
DTT BOTM WINNER
jaredc7 said:
Goals for Cafe Rebuild
- Single swing arm conversion
- Monoshock conversion
- Old styling with modern performance parts

I'm already into a couple issues and expect some custom fabrication. I'm looking forward to hearing a variety of thoughts and ideas from this forum!
I have never seen a cafe racer with a single swing arm or mono shock. Why not simply buy a modern bike?
 

oldskool

Joon-yah
DTT SUPPORTER
DTT BOTM WINNER
swan said:
I have never seen a cafe racer with a single swing arm or mono shock. Why not simply buy a modern bike?
That'd take away all the fun!!
 

jaredc7

Get busy living.
swan said:
I have never seen a cafe racer with a single swing arm or mono shock. Why not simply buy a modern bike?
Stop looking at me swan!!! Sorry, I could resist... Billy Madison gets me every time!

The main reason I went with a motorcycle rebuild instead of just buying a used Ducati Monster is because I am a very handy Mechanical Engineer, and my job over the last few years is primarily focused in project management. While its a very good and engaging job, it severely lacks in providing an engineering outlet that I've always wanted. When I was younger it was taking things apart, plastic car models, erector sets, etc. Of course I am always tinkering and fixing my car, but there have never been any real engineering challenges lately. And while my engineering degree had an emphasis in motorsports engineering, the rebuild process for an old motorcycle is just fascinating for me. And cheaper than cars!

Basically, the reasons I'm doing a complicated cafe rebuild, like Joon-yah Bourelle so perfectly stated, is because its the challenge that drives me. And because I know that I can do it! My goal isn't exactly to have a pure riding machine, but rather "one-off" novelty-type machine that's more a labor of love than anything else. The fact that I will get to ride the motorcycle after its all done is just icing on the cake for me!

PS - here are a few sites with single-swing-arm cafe racers... they're awesome!

Honda CB - http://www.bikeexif.com/honda-cb-cafe-racer
Honda CX500 - http://cx500forum.com/forum/cx-customization-modifications/21309-cx500-very-special-single-sided-swing-arm.html
W650 - http://angelandthrills.blogspot.com/2011/10/w650-with-single-sided-swingarm.html
http://forums.sohc4.net/index.php?topic=85413.0
 

jaredc7

Get busy living.
Here's a little progress on my cafe rebuild... The four pictures are from installing the new rear swing arm pivot housing... plus a little extra stiffeners ;)

I do have one question right now... Before I start designing the rear shock top mount, I am double-checking all my suspension geometry. The one thing I am having trouble researching is the sprung mass to unsprung mass ratio. I have the dry and wet weights of my bike, the travel and spring rate of my 2013 Yamaha R6 rear shock (~4.5 inches and 547 lb/in).

But in order to get the right profile of the rear shock top mount pieces, I need to know where the rear shock will be. Basically, I'm trying to find the angle of my rear swing arm with no rider, with rider, and while driving (always dynamic, I realize). Once I nail down the rear swing arm angle, I'll be able to position the rear shock, and design/fab my rear chock top mount pieces.

Soo... Is the percentage of sprung mass about 75%? Maybe 80% That should get me pretty close. Unless some of you disagree, then I'm down to weigh individual pieces that are unsprung!
 

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xb33bsa

New Member
why not just copy the aprox swinger angle of the nt650? then before final make sure you have good cornering clearance(50 degrees or so) with all front and rear suspension set to height an fully loaded as in a turn near full bump
how did you get that tube welded in straight? what kind of outboard frame tubes will you fab ? that center section is way to flexy to do the job on its own,unfortunatelly
I don't think you need to worry about antisquat too much that pertains to a bike that has some horsepower
 

cxman

Active Member
DTT SUPPORTER
easier way to do the weight thing

place the rear tire of the bike on a scale

get on the bike and have someone help you balance take the weight down

set the bike on the center stand

disconnect the rear shock from the swing arm

let the wheel slowly go down on the scale take down weight

you no have rear max sprung and un sprung weight
 

1969Honda

Member
In regards to your fork/axle swap comments don't worry so much out the stem and axle diameters. Measure out the bearing dimensions and then model up your own axle and stem. I don't think it would take much for you to figure out a bearing size that is easily available on your rims and then machine a corresponding axle to fit the forks and wheel. As for the stem, it's a actually pretty common to swap stems on the lower triple to get right combination of length and bearing size. You might be limited on your budget to the VFR wheels, but bearing conversions aren't to expensive and turning a new stem or axle shouldn't be to bad either. Also check out misumi-usa.com before you commit to a machinist on the axles, they have pretty competitive pricing for custom shafts with configurable machining options.

On your VFR rear rim, don't be surprised if you have to make any spacers to push the wheel to the right to clear the swingarm as well. IIRC correctly they are so much wider/offset differently than the NT650 you will need to add an 8mm spacer or so, surf around the build threads on customfighters.com, they've got tons of builds doing the SSSA conversions on sportbikes that you can pull applicable information from.

Keep up the good work and post lots of pics for those of us who enjoy the unusual/unconventional!
 

jaredc7

Get busy living.
xb33bsa said:
why not just copy the aprox swinger angle of the nt650? then before final make sure you have good cornering clearance(50 degrees or so) with all front and rear suspension set to height an fully loaded as in a turn near full bump
how did you get that tube welded in straight? what kind of outboard frame tubes will you fab ? that center section is way to flexy to do the job on its own,unfortunatelly
I don't think you need to worry about antisquat too much that pertains to a bike that has some horsepower
Thanks for the suggestion. I went the the Hawk 650 forum and got some info from one helpful person over there. I also stirred things up a little bit... seems there's quite a few people that are skeptical of this project! Hell, I don't blame them, the SSA and monoshock conversion is pretty alarming.
http://www.hawkgtforum.com/forum/forum/honda-hawk-gt-bros-discussions/mechanical-and-technical/639903-need-help-with-the-nt650-hawk-suspension-geometry

I had the tube welded in straight by referencing two other points on the same vertical section of the frame. The three points formed a triangle, so I got the centerline of my new tube to be the same distance on both sides from the two other points, I knew I was good.

For the outboard frame, are you talking about something that would connect to the outside of the SSA pivot like the Hawk frame does? I wasn't planning on adding anything to the outsides of the SSA, but that is a very goo point to consider, thank you.

I agree with your comment on the anti-squat, and I've gotten a similar reply from a few people in the Hawk 650 forum. It's more of an exercise in engineering that I'd like to solve rather than a practical problem that needs a solution. It is likely that my NEXT build project will need the anti-squat optimized!!
 

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