CB360 - Monoshock Brat

[compoundcycles]

Is there going to be a bar or connection between the shock mount arm and swingarm?

Absolutely.

 

[neevo]

What PJ said. My understanding is that the swingarm should be about -10 degrees from horizontal to not mess up the frame geometry too much.

 

[compoundcycles]

More work today. Seat hoop fit and welded on. Yep its going to be a stubby one. Swingarm brace...braced. I finally got to sit on it and test the spring and I'm pretty happy with it. I posted a video of me putting weight on it.

http://youtu.be/kCpIwoKlJbY

I have only one tube holding up the swingarm brace. I've seen lots of people use two, one on either side. This makes sense so there is less chance of the swingarm setup twisting. I was thinking of trying to leave it as is...but I wanted to see if anyone had strong opinions. I like the simple look. My other idea is to reenforce it with some smaller tubing on either side, ending up with 3 points of support. Check the thinner rod in the last photo.

Tomorrow: settle on the swingarm bracing, reenforce the seat, make some handlebars/seat pan/electronics tray/fenders/gas tank/or work on the motor? Soooo much to do.

 

[neevo]

Wow, I'm surprised the shock doesn't move way more than that. Either these shocks are low travel or that spring is waaaaaay too strong for the setup.

What's the general consensus as this setup is pretty close to what I'm planning.

 

[compoundcycles]

I've never ridden a RD350LC before so I don't know exactly what it should feel like. The stock wheel travel on that bike is 95mm (3.74in) and that bike is 328lbs. CB360 stock weight is 392lbs. It sounds like with the motor in there...and my setup being close to the rd350 design I shouldn't have any problem getting some flex out of this shock.

I'm super stoked with how it turned out and I think its gonna ride great when its all finished.

 

[neevo]

Fair point on the motor, I think that will get the shock flexing a little more.

Looking good!

Just looking to order my shock at the moment and thinking of going for an upgraded spring as the CB is a good 15kg over the RD350LC, not even sure of the effects of a GSXR front end and upgraded swingarm.

Care to do another video when you have the motor back in?

 

[trek97]

Its just freakin cool.

 

[teazer]

I suspect that the shock on an LC is mounted closer to teh pivot so teh leverage is completely different. Geometry matters.

I hope that the rubber bushes are not still in the swingarm. If so the brace will flex slightly and will probably fatigue the front welds.

 

[compoundcycles]

Thanks. Yeah, I'll post another video once the motor is in.

I have some bronze swingarm bushings on deck to replace the stock rubber ones. Once everything is cleaned up I'll install them.

 

[crazypj]

I don't remember the exact number but I'm pretty sure the leverage ratio is around 1.7~1.8:1 on RD350 LC.
When I did 400, shock was way too stiff
As I said earlier, I had to extend swing arm mounting up and back. (moving bolt closer to tyre)
You don't need or want a 'straight' push, a longer 'loop' holding shock with revised mounting may be required.

 

[neevo]

I don't remember the exact number but I'm pretty sure the leverage ratio is around 1.7~1.8:1 on RD350 LC.
When I did 400, shock was way too stiff
As I said earlier, I had to extend swing arm mounting up and back. (moving bolt closer to tyre)
You don't need or want a 'straight' push, a longer 'loop' holding shock with revised mounting may be required.

Really PJ?

So getting an uprated shock is a big mistake!!!

Might let the missus know before she buys it as an Xmas pressie.

Any thoughts on the affects of an USD front end too? Seems like the front might be way over sprung too considering the GSXR 750 is a 200kg bike. Should be able to dial back some preload but I think spring change all round might be in order.

 

[trek97]

I hope that the rubber bushes are not still in the swingarm. If so the brace will flex slightly and will probably fatigue the front welds.

Teazer is talking about the rubber bushings in the shock mounts of swingarm. not the swingarm bushings themselves.

 

[crazypj]

Really PJ?

So getting an uprated shock is a big mistake!!!

Might let the missus know before she buys it as an Xmas pressie.

Any thoughts on the affects of an USD front end too? Seems like the front might be way over sprung too considering the GSXR 750 is a 200kg bike. Should be able to dial back some preload but I think spring change all round might be in order.

I think GSXR is a little undersprung?
You can tune it out with various adjustments to work with 400.
Personally I don't like too much dive under braking so tend to have my bikes set up a bit stiff

 

[neevo]

Good stuff. I prefer a heavier sprung/preload setup anyway. Cheers!

 

[compoundcycles]

Cleaned, Blasted, and Primed the footrests.

 

[compoundcycles]

Working on the seat...

 

[compoundcycles]

more seat...

Does anyone know of a place that will cover a seat pan with foam and cover if you send it to them? Because of the shape in front I think I'd like to have a professional do it. I tried a quick version with the original seat vinyl and I don't like it at all.

 

[VonYinzer]

Alchemy Upholstery here in Pittsburgh. Jim is an AWESOME guy and super talented.


http://www.alchemyupholstery.com/

 

[1969Honda]

How'd I miss this one, I'm subscribed and in now!

 

[MotorbikeBruno]

Yup I missed it too! Just started on a cb500 project and my brother-in-law and partner in motorbike crime is pushing me towards a monoshock too. Killer build so far man. I enjoyed going through it all up to this point. Now hurry up and finish so I can learn more... ;D