1979 CB750 DOHC Monoshock Build
- Thread starter bananas
- Start date
Earlysport
New Member
I"m in the middle of a mono shock conversion and hence have done quite a bit of research. I've also played a lot with car and mountain bike suspension in the past. You can check my thread XS400 Cafe Modern for my approach, which was to implement the full 05 GSXR linkage and factory shock along with the swingarm. That required a totally custom rear frame section and a lot of other frame work however.
An issue I see is the Ducati 800 SS has a falling rate rear suspension, and your design has a rising rate. That means shock valving will probably be some way off, and it will also be further off having changed spring rate. I think it'd be worth you sourcing a shock that operates in a similar plane (although I have no idea of a factory bike that does. Alternately a decent fully adjustable shock initially valved for your desired spring rate might do the job.
In my build I also went for a 525 chain as it's narrower than a 530, and in hindsight I'd go with a 520 for even more clearance. They do 520 chain conversions for 150 hp super bikes so no issue with strength! This might help you with your chain clearance concerns.
Cheers,
Earlysport
Yamaha XS400 DOHC build, future CB750 build, Ducati 996R
An issue I see is the Ducati 800 SS has a falling rate rear suspension, and your design has a rising rate. That means shock valving will probably be some way off, and it will also be further off having changed spring rate. I think it'd be worth you sourcing a shock that operates in a similar plane (although I have no idea of a factory bike that does. Alternately a decent fully adjustable shock initially valved for your desired spring rate might do the job.
In my build I also went for a 525 chain as it's narrower than a 530, and in hindsight I'd go with a 520 for even more clearance. They do 520 chain conversions for 150 hp super bikes so no issue with strength! This might help you with your chain clearance concerns.
Cheers,
Earlysport
Yamaha XS400 DOHC build, future CB750 build, Ducati 996R
bananas
Been Around the Block
Hey Earlysport,
Thanks for the info. Love your bike! I'm actually sub'd to your thread, haha. I've actually been thinking of switching the shock out to something very similar to how yours is setup.
For now I'm getting the bike towed home so I can finish up the electrical system and build a seat/pan.
Cheers!
Thanks for the info. Love your bike! I'm actually sub'd to your thread, haha. I've actually been thinking of switching the shock out to something very similar to how yours is setup.
For now I'm getting the bike towed home so I can finish up the electrical system and build a seat/pan.
Cheers!
biker_reject
Over 1,000 Posts
Really diggin' it. Also, I like your rear sets!
bananas
Been Around the Block
biker_reject said:
Thanks! I chose the Tarozzis for what I would consider their subtle OEM appearance. Glad you like em.
So we've reached my favorite stage of any build. Just before any major stylization where the design possibilities are still somewhat endless.
Just for fun, I thought I'd do a set of before/after comparison photos.
Ass:
Not bad, however I found the wide K-Series (Touring) gas tank was hard to grip with my legs. Combined with the clubmans I found it was difficult to maneuver -- especially at low speeds such as parking lots or in traffic. Being somewhat of a newer rider and rather small-framed probably creates this this problem.
A shot of the new rear. The new '80 F-Series (Super Sport) gas tank cuts 1.5" inches from the width at the front and 1" at the rails. This shot also really emphasizes the new beefy 180/55/R17 tire vs the old 130/90/R18. The bike's lean angle is drastically increased. Will figure out by how much once she's running.
One sacrifice visually is the superbike bar/ risers, however the major increase in comfort, control and my own confidence really makes up for this. The control set-up is completely bespoke and built around my own proportions. The setup is extremely comfortable.
Right Side:
This was my favourite angle of the bike previously. My wallet tells me I probably should've left it here... hahaha.
I'll admit I got a bit carried away with the suspension upgrade... The new wheelbase is 59", 1.7" longer than stock. The new seat rails are at 29.5" high (with a planned 2" +/- seat), compared with the stock bikes' 32.6 inches.
Another result I am very happy with is the new seat frame. I've always held a dissonance about the infamous 'triangle' -- on one hand it exists on almost every 70's bike platform, obviously there to support the twin shocks, yet I've always felt it visually detracting from the bikes more significant lines. Credit for the new design goes to Adam at AMT Machine Shop here in Vancouver.
Visually, the SRAD GSXR 750 swinger is a bit beefy and I'm thinking a coat of a flatter shade of black will assist in this de-emphasis. For the sake of design continuity, the frame gussets will receive a tiny bit of adjustment.
Flattering Angle:
I'll admit the side profile was fantastic at this point, however the very wide tank was rather uncomfortable for my 5'6 frame (28.5" inseam)
My favourite angle at the current stage of the bike. For some reason seeing this makes me just want to hop on and ride. I consider this mission accomplished.
bananas
Been Around the Block
750mors said:
Hahaha. I've come to the realization that your F-Tank is the superior choice. K would've looked great as a tracker but I'm wanting a slight cafe hump. BTW how's the riding season over there in Australia? The rainy season is about to begin over here
StoleOne said:
I'm still learning from scratch how this whole process works. There are some great posts over in the 'Electrical' forum. BTW, if you're still looking for parts, 'Mark13018' on the forums has the best deal on wire. Moto-Madness has the cheapest M-Unit and I'll probably be getting my connectors from VintageConnectors.com in the next day or so.
The M-unit will eliminate your need for fuses, LED flasher relays. The rest of everything else can be wired directly into its individual slot. Some cool things are programmable headlight/tailight/signals and the alarm system. Still learning and absorbing info so I'm sure there's a bunch of stuff that I've missed.
