Topic: '82 cb650sc cafe project

[kerryb]

Yes I would say better.
The angle of the shocks may be a bit too far forward though.  To check for proper top post location, use a ruler or string from the forward swingarm pivot point, back to the lower shock mount on the swingarm, then (keeping the forward end on the pivot point) rotate the other point up to the frame and see where it lands.

I agree, the shocks "appear" to be leaning too far forward.  I've been stuggling with this design issue from the beginning.  If I get longer shocks, that allows the tops to reach the new top tube (the hoop) and still hold the frame up where it needs to be.  My other option is to move the lower mount further forward.  But that will bring with it a change in geometry that will affect spring rates, and I only want buy 1 new set of shocks!
So... help me pick the right set of new shocks, l'll measure the length, and depend on the collective expertise of the forum to select a good spring/damping rate in a reasonably priced/performance shock.  Keep in mind, i've never ridden a modern sport bike or a new shock (except on my harley) so I have no credentials for selecting a shock!  Where do we start?  Rider weight, swingarm length, angle of the shock off vertical, or some mystical mix of all of these.  What is the specs of the stock shocks? Is that knowlege even helpful?  I figure the budget is as large as the profits from selling off the tank, seat, sidecovers, and other bits that will never go back on this bike.

When I get out to the shop later, I'll do the string arc method to test your theory.   

[Godffery]

After finding your top mount location, position the swingarm so that the front sprocket shaft, Swingarm pivot pin & axle are all in alignment. Then measure the distance from the newly established top shock location, to the lower shock mount on the swingarm. (I'm guessing it will be in the ballpark of about 13 or 14"?) That will determine your ideal shock length.

[kerryb]

so many factors, and no engineer in sight...oh well, here goes.  So I lined up the driveline parts(sprocket, swingarm pivot, and axle) set the back wheel on the lift, relaxed the straps on the fork so it could rebound, and put the new shock mount/gusset where I wanted to see it, and measured the desired shock length.  Near as I can tell, the shock length should be 14.125" to 14.25".  I'd rather have the shocks too long than too short, so I found 14.5 inch shocks for a low price on DCC website.  These are rated for 365 lbs per shock.  Do I now put the engine back in so I can weigh the back end of the bike to add the rider weight to it?  Note: I still have the triple trees dropped down the fork tubes 1 1/2", so maybe a 14.5" shock is actually the right length.  Probably need to put some 14.5" struts on it and measure to seat height to make sure we can still reach the ground.  (I'm only 5'8" and shrinking!)

[calj737]

Don’t buy those crappy shocks. Do yourself a favor, and spend enough to buy some decent shocks. They make ALL THE DIFFERENCE in riding your bike. Contact Nils @ Restocycle for an SOHC discount.

[kerryb]

I knew somebody was going to tell me that!  Okay, okay...I'll contact Nils and do the right thing, but only because you said it's the right thing to do.  If it weren't for the wisdom and generousity of this forum, I wouldn't be this far along in my training and successes. 

[Godffery]

There are so many Crap shocks on the market today, it caused a fails gauge of what to expect for the average shock.  So as a reference, Just about any Good set of shocks will start around $400+. If you find something (No name or off brand) that "looks" good, for less then that, chances are they are crap. =/

[kerryb]

I got a nice reply from Nils offering a cbx shock at 14.3".  Two versions, adjustable rebound or not.  Then I noticed they are eye to eye, not eye to clevis which my frame is set up for.  Now what...am I missing something obvious, or did I not supply the right info?  The cbx weighs more than the 650, do I need to consider spring rate in this choice?

[Godffery]

   Stock CBX has the clevis.

 https://partstream.arinet.com/Image?arik=Vkgcs9tma3XMhDIifYPQ&arib=HOM&arim=oQP8CsBN5kh1yW4tp4C9BQ2&aria=Za0_M9PGk7WRoCUgOvFMRA2&ariz=3&ariv=https%3A%2F%2Fwww.midwestactioncycle.com%2FOEMpartfinder.htm

https://www.midwestactioncycle.com/OEMpartfinder.htm#/Honda_Powersports/CBXA_(80)_SUPER_SPORT%2c_JPN%2c_VIN%23_SC03-2000021/REAR_SHOCK_ABSORBER_80/CBX-80-JPN-A/2Y144220AF1442202501A

[kerryb]

Well thats a color of a different horse!  I sent a reply to Nils indicating my confusion.  We'll have to wait and see what he says. 
The picture he linked me to showed eye to eye, hopefully just a typo, or my poor eye skills.
In other news, hows this?  Started a headlight/name badge mount.

[kerryb]

Another email to Nils and we have settled on the Ikon cbx shocks.  that means we need shock mounts...so here goes, I think I have it figured out.  You can't buy these at dime city, but I can steal their idea!  I guess the real trick will be making the other side match!

[kerryb]

So I got the welding done and the shocks mounted.  Looks like I need to get the engine back in and a rider on it to see where it sits.  I may be able to stick with stock shock length after all.
Also practicing my sewing in preparation for a seat cover!

[Hutch]

Your frame modification looks great.  What tank are you using?  I was able to mount a tank from a '81 CB650 custom by relocating the front tank mounts.  It will also allow you eliminate the vacuum assisted petcock.  The only thing to look out for is the petcock clearing the motor.  I barely made it...

[Hutch]

Don't know what your pan is for the air box with the frame changes.  I made an adapter to fit a large pod filter.  I kept the stock cv carbs, this set up works fine since I didn't attempt to eliminate the plenum.  This allowed me space to relocate the battery, I mounted the rectifier to the bottom of the seat pan.

[kerryb]

Your frame modification looks great.  What tank are you using?  I was able to mount a tank from a '81 CB650 custom by relocating the front tank mounts.  It will also allow you eliminate the vacuum assisted petcock.  The only thing to look out for is the petcock clearing the motor.  I barely made it...

I'm using a '78 CB750k tank with slight mods to the frame mounts.  The petcock clears ok with the CV carbs or the pd42a's from the same '78k.  wish I could find a petcock with a rear outlet or just run the hose around the rear of carb #1.  Not sure which set of carbs will be final as the 42's will require a new rack and linkage to work, but there is plenty of room to make a new custom airbox. 
The last item without a plan yet is the battery.  Either mount the stock battery somewhere in the rear triangle or research a super small one that is still capable of running the starter motor because there is no kickstart, but plenty of room under/in the seat and cowl.

[Hutch]

Your frame modification looks great.  What tank are you using?  I was able to mount a tank from a '81 CB650 custom by relocating the front tank mounts.  It will also allow you eliminate the vacuum assisted petcock.  The only thing to look out for is the petcock clearing the motor.  I barely made it...

I'm using a '78 CB750k tank with slight mods to the frame mounts.  The petcock clears ok with the CV carbs or the pd42a's from the same '78k.  wish I could find a petcock with a rear outlet or just run the hose around the rear of carb #1.  Not sure which set of carbs will be final as the 42's will require a new rack and linkage to work, but there is plenty of room to make a new custom airbox. 
The last item without a plan yet is the battery.  Either mount the stock battery somewhere in the rear triangle or research a super small one that is still capable of running the starter motor because there is no kickstart, but plenty of room under/in the seat and cowl.

My '81 petcock has a rear outlet, not sure of the thread size.  There's always pingel, but they are $$$.  A small battery tucked under the seat would be ideal IMO.  I went with a Shorai lithium which is damn near the same size as the stock battery since I didn't have any more room under the seat.

Honestly, the stock CV carbs where not the nightmare I thought they'd be.  Although the air mixture screws on carbs 2 & 3 are a pain in the ass to adjust once the carbs are on.

Following your progress intently.  Your work on the frame has me considering going full on cafe style with the same frame mod, but then I might have to figure out how to replace the stock comstars with a set of 18" spoke wheels  .

[Hutch]

Not to sidetrack the rear suspension and carb discussion, but what are your plans for handlebars since the SC has through bars.  I wound up shaving the excess material off of the top yoke and mounting clip-ons.  Top mount bars would have been ideal, but I didn't think it was worth the expense of ordering a custom made yoke since I was keeping things simple.  I also considered riser bushings, like some Harleys, but I need a new home for the ignition switch which I mounted in one of the holes using a set screw.

[kerryb]

The handlebars we have now were cut from a pair of old apes in my stash.  They had just the right bend between the riser and the grip.  They have about 4" of height adjustment, and in the current location, place the grips approx where superbike bars would be.  Gauges are white-faced from another cb750 (80's) and the ignition will probably remain in the stock position.  Current plans are to put a bank of idiot leds on the triple and one big red led in the steering tube opening.  The most significant change planned is the new headlight (smaller) which will have no wiring in it except the two wires to power the light.  These changes can be seen in earlier posts on this thread.

[kerryb]

I couldn't start the seat pan until the tank mount was finished, can't believe how long that took me.  With all the overthinkin' I'm wondering if I missed something.  This is my first tank engineering job.  So take a look and see if there are any details I missed or should change before final welding takes place...please.
Mounting pegs in front were dropped and shortened to accept the '78 cb750k tank.
Rear mounting plate created to hold the rubber feet and provide a rubber cushion to clamp against.
current clamp is a strip of aluminum bar into an existing threaded boss.  I think a more substantial clamp will be made for greater purchase on the tank.

p.s.  If some fool in the future decides to stand on the seat and tank, I don't want the tank coming loose!

[calj737]

If the ally plate at the rear is bolted to the frame, and the tank is bolted to it, you do not need the “strap” to secure the tank. And the plate looks plenty strong as is.

[kerryb]

The plate is mild steel, about 3/32", but tank is not bolted to the plate. 
Haven't decided yet to weld the plate on or just use the bolts.  So a clamp is still needed.

[kerryb]

Thanks for the input calj737,  time to move on to electrical component placement so I can figure out the seatpan and space needs under the seat.  I would rather not put the weight of the battery in the seat hump, just seems wrong on a weight distribution principle.  Other suggestions welcome...   

[calj737]

Any battery that will fit in the hump won’t weigh diddly. For true, best weight placement, low and central is ideal. But not from a fabrication point of view. Or styling.

[kerryb]

The battery will be a compromise with a nice battery box mounted just above or on the swingarm.  Maybe even have the starter solenoid hung off the side like a reservoir on a shock.
So I tacked on a cross brace between the shock mounts and made a tray to play with electrical placement.  What I've discovered is there is enough room for the igniters under the tank.  The fuse box can be much smaller with blade fuses.  Which brings us to the voltage regulator.  A) Are the rubber isolation mounts imperative or just a good idea?  B) Does the Volt reg generate enough heat to warrant mounting it under the tray in the airstream, or is placing it in the semi-protected tray under the seat ok?

[kerryb]

Had this idea for mounting the seat rolling around in my head but couldn't decide how to carry it out.  rummaging through the scrap box and came across the original frame brace cut from the bike earlier.  looked a little closer and found some tubing with the right ID. for the "feet" to sit on the frame rails.  the feet will be lined with neoprene rubber, and the brace will be glassed into the seat pan.  resulting cavity underneath should allow plenty of room in the electrics tray....progress.

[kerryb]

It's probably overkill, but hey what do I know, it's my first one!  Finished up the backbone for the café seat.  Added a plastic bumper tab for the original seat mount pocket, a "spine" to keep the front in line during glasswork, and a rear cross brace with two mounting studs that fit the frame.  Couple of wingnuts with lock washers should be all I need to hold the seat on and still be able to remove it without tools.