1977 CB750 F2 Super Sport

Alright. Now this is giving me a headache...

I plan on keeping the front stock 19". I'm giving in to going to a smaller wheel/tire on the rear, but where do I start? Here's what I'm looking at:


http://cgi.ebay.com/ebaymotors/cb-750-honda-k-wheel-rear-wheel-_W0QQcmdZViewItemQQitemZ130413300165QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_956

http://cgi.ebay.com/ebaymotors/REAR-HOG-WHEEL-16-SPOKE-ASSY-HONDA-CB750-DRUM-CHOPPER-_W0QQcmdZViewItemQQitemZ110577214007QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_1495wt_941


http://cgi.ebay.com/ebaymotors/Honda-CB750-Rear-Wheel-Straight-Rim-_W0QQcmdZViewItemQQitemZ260496124651QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_956


http://cgi.ebay.com/ebaymotors/HONDA-REAR-WHEEL-250-17-SPOKE-_W0QQcmdZViewItemQQitemZ400121203004QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_500wt_1182
 
Ok stock front is 1.85 x 19 and rear is 2.15 x 18. The only issue i see with a wider rim is chain clearance. a wider rim 2.50" to 3.00" will accommodate a larger tire 4.00 and up. The larger rubber the higher the chance of chain clearance issues. You may want to mount the hub and see how much width there is to play with. and if offset sprockets are in order.

On the diameter, others have drilled a hole in one end of a piece of scrap wood, cut to length desired, and mounted on the axle. Strut the swinger to max expected compression, and spin the wood to check clearance.

Now my stock 18 x 2.15 with a 4.00 tire gives me a tire dimension of 4" wide and 3 1/4" from the shoulder of the rim out. I would measure the radius from the axle, but I can't find my tape measure.

Food for thought.
 
Here's some tire info I borrowed from Dunlop. First is the listed tire size, then the recommended rim width, then the tire height and last the tire width (typically mounted on listed rim size) Divide the height in half to see how much clearance you gain, and you'll see the difference from the first tire and the last tire you would gain 1/2 an inch. There are resources everywhere on deciphering tire sizes but basically it's tire width (in mm)/sidewall height as % of tire width/rim width (in inches). The 'old' way of 4.00-18 tells you nothing about the sidewall height. That's 4" wide and mounts on 18" rim. Have to get height info from a manufacturer, but I think you'll find the aspect ratio is often 100%, so the sidewall is probably 4" tall.

130/90B16 3.00 24.95 5.25
140/90-16 3.50 25.70 5.60
150/80B16 3.50 25.25 6.19
140/80B17 3.50 25.60 5.63
150/70B17 3.50 4.00 25.22
120/90-18 2.50 2.75 26.50
130/80-18 3.00 25.95 5.10

My route is usually pick your tires and wheels, then make the vehicle fit them because they make or break your look in my opinion, and as you've stated. Again, I defer to Carpy. You can have a look at several of his rides on cb750cafe where he's gone with a nice, fatter 16" rear - though fatter can also mean taller as you see above. I know he's fit a 140/?/16 tire on a CB750, but I can't recall if any mods were required. Hate to say it, but I'd be looking at modding the rear hoop/battery box til you can get your 4" of travel on the wheel/tire combo of your choice. Unless of course you're a big guy, in which case jack your rear end up with taller shocks and/or relocate your upper (or lower) shock mounts. Moving the lower mount will require a spring rate change though. Lots of options... sort of. I don't want to interfere with your creativity, but I'll try and save you some pain if I see it coming.
 
Man that's a wealth of info jlgace. Thanks a bunch.

So I just took some measurements and got off the phone with the YSS guys.

eye-to-eye at full extension: 13.25"
eye-to-eye at compression, just before bottoming out: 12.25"

So I have a total of 1" of travel. Awesome. He told me I was crazy, and though they could make a shock with a tighter wound coil and a damper to prevent the tire from hitting the tray, he suggest I get a smaller tire or get rid of the battery tray. I'm pretty sure I'm not going to be doing the latter, so 16" x 3.5 rear wheel it is. Damn I hate the way that looks, but I guess I'll have to live with it. There are just too many options... I can go taller on the shock, mount the lower shock mount on the new swingarm a little closer to the pivot to gain height, cut the battery tray from the bottom of the frame rail, and weld it to the top... I just don't know what to do yet, but I'm itching to get on this thing and ride.
 
I would suggest starting by determining the compressed length of the shock you were going to use, compress the suspension until the tire hits the tray (with the 18" or whatever tire you want to use) and measure the shock length in that position. The difference is how much clearance you need to gain (plus a safety factor for tire growth etc.) and then you can look at your alternatives. If you know you only need an inch, you can get a shock with a 1" longer body without losing travel. When I've seen these rear trays used, iirc the batteries are often the optima-type and mounted on their side probably for this reason. Very surprised the seller (Benjies) hasn't thought this out more. If you're willing to do some cutting and welding there's no need for you to lose all your suspension travel. I would even resort to removing the tray and rewelding to mount on top of the loop if necessary as long as the battery height doesn't interfere with the cowl. My $0.02. And like somebody said before and I'm sure you know, 1" won't cut it. That's next thing to a hardtail.
 
Thanks everyone for all the input on the rear clearance issue. Benjie isn't to blame for the supposed "design flaw." Just another thing to add to the "Things I'll need to change there when I make a change here" list ;)

So just for the hell of it, I went down to the local scrap yard to look for some taller shocks. First pair I found worked! They didn't have a price on them, so I asked the parts guy to hook me up. Final price for the pair: $60. They came off an 81 CB750. 14.25" eye-to-eye. I set the damping adjuster up, and also preloaded the shocks all the way. I've gained an additional inch of travel, and so far I have no problems bottoming out.

I took lots of pics over the weekend, after rebuilding the wiring harness to extend the electronics underneath the seat cowl. I also got a ton of parts that shipped last weekend... More of those pics soon...

Just for the hell of it, and until I could get the new Benjie oil tank on, I unscrewed the stock oil tank and twisted it sideways. All was awesome, until a kink in the hose spewed oil everywhere when riding. Woops.

After a quick blast of black paint to match the rest of the bike:

750-525x393.jpg


7502-525x393.jpg
 
It is really coming along Raf. I like love the stance of the new shocks. I knew you'd work it out, and glad it didn't cost 500 bones.
 
Christmas in August! Tons of parts shipped last week:

New solid state regulator/rectifier. Hopefully this will fix my battery charging problem. Set to rectify voltage to the battery at 14.3V.
DSCN1392-525x393.jpg


New ratcheting crimp tool and stock male/female connectors:
DSCN1393-525x393.jpg


Progressive front springs from Dynoman:
DSCN1394-525x393.jpg


Tapered stem bearings from Dynoman:
DSCN1396-525x393.jpg


Dyna S ingition, 3ohm coils and wires from Dynoman:
DSCN1397-525x393.jpg


First thing's first: Rebuilding the wiring harness:
DSCN1385-525x393.jpg


Since the above picture, I have redone the butt connectors with slimmed down butt connectors and the ratcheting crimp tool. Heat shrink to insulate. Haven't uploaded those pics yet, but I'll get to it this week...
 
CresentSon said:
It is really coming along Raf. I like love the stance of the new shocks. I knew you'd work it out, and glad it didn't cost 500 bones.
Click to expand...

Thanks man! Yeah, the thing I was scared of was having a high back-end, but it doesn't really look all that bad. Not only that, sitting on the bike takes up a bit of travel while still providing enough cushion while riding - and not bottoming out. Stoked.

btw - glad you like your new parts. Now let's see some pics! ;)
 
Oh yeah... Also took out some anger with the help of the cutting wheel...

DSCN1398-525x393.jpg


DSCN1399-525x393.jpg


Goodbye seat lock...

Does anyone know if JB Weld or Body filler will hold up to powder coating temps? I got as close as I could get, but grinding off these tabs has left some pretty rough grooves that I want to fill in before sending the frame to powder...
 
JB weld will "sometimes" take one cure cycle, but it is known to outgass, i typically will braze parts in that need coated, but in a pinch JB weld will work jsut depends on what powder your coater is shooting and what temps and cure cycles he is running. i would sugest calling him i know we will perfer to do stuff like that ourselves so we can stand behind the work.
 
JRK5892 said:
JB weld will "sometimes" take one cure cycle, but it is known to outgass, i typically will braze parts in that need coated, but in a pinch JB weld will work jsut depends on what powder your coater is shooting and what temps and cure cycles he is running. i would sugest calling him i know we will perfer to do stuff like that ourselves so we can stand behind the work.
Click to expand...

Good to know! Thanks :)
 
Dropped the rims and hubs to the powder coater today. I was also going to bring in the front and rear calipers, but I'm having a hard time deciding whether or not to blast and polish? Or powder coat? Right now, the rims are powdered black. Stainless steel spokes and nipples. Hubs powdercoated black. I'm thinking I should polish them, but I also want to polish the fork bottoms, and the new boxed swingarm will also be polished. Decisions, decisions...

I'll post pics when I get the wheels finished. ~2 weeks...
 
rafanomenon said:
Christmas in August! Tons of parts shipped last week:

New solid state regulator/rectifier. Hopefully this will fix my battery charging problem. Set to rectify voltage to the battery at 14.3V.
DSCN1392-525x393.jpg


I have that same reg/rect on my K8 and along with a odyssey battery, I have had no charging issues at all. Starts up oh so well and nver had a issue with charging. Well worth the money!
Click to expand...
 
Milehighcb said:
I have that same reg/rect on my K8 and along with a odyssey battery, I have had no charging issues at all. Starts up oh so well and nver had a issue with charging. Well worth the money!
Click to expand...

So far, so good! I wouldn't trust those 30+ year old electronics. Definitely a worth while upgrade, and a great warranty!
 
Bike looks good! I like the look of having some open air around the rear tire. Did you notice if the bike was more willing to turn after raising the rear? I actually don't mind the comstars on it. Your spokes will be much cooler though I think...
 
jlgace said:
Bike looks good! I like the look of having some open air around the rear tire. Did you notice if the bike was more willing to turn after raising the rear? I actually don't mind the comstars on it. Your spokes will be much cooler though I think...
Click to expand...

I did notice a little bit of a change, but not much to go crazy over. A few months ago I had some Vipex reservoir shocks on there that dramatically increased handling. I think they were 2.5" above stock? Made my bike look silly though, so I had to find a compromise...

dsc00528-525x393.jpg
 
Warning: Some serious bad assery ahead.

I've always dreamed a 650 bobber project. This past weekend my dreams came true. Say hello to project #3: Brown Bomber Bobber! (link to build posting soon in 'bobbers')

DSCN1423.jpg



Welp. There goes time and money into both my 750 and 175 builds... ;D
 
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