biker_reject
Over 1,000 Posts
Very cool, very cool!
1979 CB750 DOHC Monoshock Build
- Thread starter bananas
- Start date
bananas
Been Around the Block
trek97 said:
Haven't fitted a chain yet -- actually still picking one out. Although the axles match perfectly, a big problem with the GSXR swingers on these CB750's is alignment and the chain.
We were able to center the swinger perfectly through a ton of fitting and removing material. A chain will clear -- just perfectly, however when off the bike it does comes pretty close to the guard. Worst case scenario I'll add a chain tensioner but it shouldn't be a problem.
Nice. Seen a number of guys do a ton of work and in the end they say "DOH!!!" didnt consider a chain went on this thing. Its crazy how easily things like that can get overlooked.
Im glad you had it in mind from the start. Thats more than half the battle, WON.
Im glad you had it in mind from the start. Thats more than half the battle, WON.
bananas
Been Around the Block
trek97 said:
Thanks for looking out! Due to the nature of my work (architectural design) I'm a bit paranoid and as a result somewhat meticulous by nature -- also why this build is moving so damn slowly. Gorgeous sun all around and I'm stuck traveling in a cage!
pukhkan said:Awesome build bananas!!!
been thereforgot to consider air filters on my bike
That's hilarious! I had also forgotten about the air filters but luckily the shock just clears (by a few millimeters). Thanks!
alexfisher7
New Member
HI bananas
Good job indeed,
I am looking to do a monoshock conversion myself. Beside the all monoshock fitting/fixing malaka, how easy was it to fix the gsxr swing arm? any mods needed on bearings and fixings?
I am up for mods on the frame itself but don t have the gear to work aluminum so....
Good job indeed,
I am looking to do a monoshock conversion myself. Beside the all monoshock fitting/fixing malaka, how easy was it to fix the gsxr swing arm? any mods needed on bearings and fixings?
I am up for mods on the frame itself but don t have the gear to work aluminum so....
bananas
Been Around the Block
750mors said:
Thanks Matt. Love the build. We DOHC owners have got to show up those inferior SOHCs! Its funny.. I've been building this for over 2 years now and you're way ahead of me -- awesome!
Here's a photo of the shock mount (best I have on me -- out of country and away from the bike). Its basically a series of gussets, about 2.5 inches down, connected to the stock horizontal brace/tank mount location. Originally we had created a mount directly to the tank mount -- however the bike ended up having about 3 inches clearance and mushy suspension travel. It functions well at the new location, albeit stiff. I'll get more photos of it in the future but I assume you've figured it out already!
More recent.
cklamer said:
Awesome, good to know this is possible! Love that BCR setup on your bike and rad paintjob!
xb33bsa said:
Good point! She's definitely the longest thing I've yet to ride. Thanks!
alexfisher7 said:
Fitting the GSX-R swingarm wasn't particularly difficult. The stock axle actually just kind of... fits. However the major difficulty with this one is centering the wheel. Most bikes you see aren't centered -- they're actually a couple mm off. Another major difficulty was was finding a offset front sprocket to get good chain clearance. Ended up welding two sprockets together. In hindsight I should've just measured and had a custom setup made. The rear 530 sprocket is from a 2001 GSXR 1000. It's important that I can do some canyon carving on her so I went a little overboard but very happy with the results. All-in-all I kind of should've went for a dual Ohlins setup... probably handles better... However I've heard somewhere that monoshocks get you laid. 8)
DylonDylonDylon said:
Thank you sir!
bananas
Been Around the Block
750mors said:
We used a trial-and-error approach for the bike. The shock is from a 2006 Ducati 800 SuperSport -- the reason being I had wanted to install it as a diagonal/horizontal monoshock from the upper swingarm brace to the tank mount area. The Ducati has the same set-up as this. However, the machine shop I am working with was adamant that brace wouldn't be strong enough (I trust this guy -- he knows what he's talking about!). We ended up mounting down low, nearer to the axle, forcing a vertical setup and making the shock geometry a bit wonky. The stock Ohlins dual-rate spring was having issues so we swapped out to a heavy-duty spring. Works fine now.. I would say about 90% of the way there... she's now ridable with very good clearance.. however it probably could still use a bit of tinkering and fine-tuning. All in all I probably shouldn't have used this particular shock...
For me I've taken this is a very interesting learning experience and a crash course to shock geometry. The important point is to have the shock react at the angle it is originally intended to -- usually the shock wants to compress at a 90° angle relative to the bottom mount and overall swingarm movement. It's funny after all this I realize most of those BikeEXIF mono builds are actually done incorrectly -- a lot of them aren't actually ridable (too stiff or too soft).
750mors
Been Around the Block
Funny that you mention the BikeEXIF builds as I too have been looking at them wondering how on earth they actually function.
I'm going to have to get a spring custom made for my setup so hopefully I can get it in the ball park first go, but that's the risk with one-off builds hey!
Keep up the great work, it's keeping me motivated!
Matt
Sent from my iPad using Tapatalk
I'm going to have to get a spring custom made for my setup so hopefully I can get it in the ball park first go, but that's the risk with one-off builds hey!
Keep up the great work, it's keeping me motivated!
Matt
Sent from my iPad using Tapatalk
bananas
Been Around the Block
Got some photos of the shock-mounting locations for anyone curious:
Still missing a bit of frame strengthening in the area. I do plan to do some hardcore riding on her so there is still a chance I will end up adding a linkage setup if I feel like she doesn't handle as well as I'd like. Unlikely, but worst case scenario will be utilizing the OEM GSXR 750 setup.
Still missing a bit of frame strengthening in the area. I do plan to do some hardcore riding on her so there is still a chance I will end up adding a linkage setup if I feel like she doesn't handle as well as I'd like. Unlikely, but worst case scenario will be utilizing the OEM GSXR 750 setup.
