Topic: 1974 CB550. Racetech Monoshock. JMR Head. Built Engine. "BLAC"

[BLAC]

Man that seat looks nice.

Thanks man!  I'm really happy with it!

[BLAC]

I think im going to need 14.5in shocks... fully bottomed out shouldnt be shorter than 10.25 (or else ish will get real..)

What I have done to get these numbers is measure center of eye to eye a little above where I would like the ride height to be and then when down to where the rear wheel starts to get intimate with the seat loop.  That range gives me a spring of 14.25" - 10.25"

Does that sound like im thinking about it correctly?
 

I agree.  The only reason you would want to adjust the subframe supports is for rear wheel clearance.  As an alternative, you can keep the line of the tank and seat uniform and use 750-length shocks.

[SOHC4 Cafe Racer Fan]

That sounds like adequate clearance.  I guess you'll know by road testing.  Keep on keeping on.

[BLAC]

That sounds like adequate clearance.  I guess you'll know by road testing.  Keep on keeping on.

I just dont want to test by buying more sets of rear springs that end up not working lol

Anyone interested in stock length, brand new, Hagon springs? =(

[SOHC4 Cafe Racer Fan]

That sounds like adequate clearance.  I guess you'll know by road testing.  Keep on keeping on.

I just dont want to test by buying more sets of rear springs that end up not working lol

Anyone interested in stock length, brand new, Hagon springs? =(

I'm sure you can sell them quickly in the Classified's section.

[redwillis1978]

Your assumptions includes a zero weight rider or infinitely stiff springs?

You could achieve the same look by adjusting the tank mounts once the geometry was correct.

If your total shock travel is about 4", that's 2 up/down. At ride height your ass end is going to be dragging.

[redwillis1978]

[GV1390]

Looking good homie! Glad you're taking a stab at trying things out on your own, it'll be rewarding in the end.

[Tews19]

Subscribed. I once attempted a frame.mod like yours. Let's just say I have a stock fram now.

[BLAC]

Subscribed. I once attempted a frame.mod like yours. Let's just say I have a stock fram now.

Haha thanks, I hope it turns out.  I'm debating on a monoshock conversion... I love the lines of the subframe and would love to run a monoshock setup that slows the rear to stay open and uncluttered. I just need to do a lot of research on the proper geometry for that...

[Camrector]

Mike le at Kinetic makes a weld on kit for a monoshock cb550 conversion. Might be worth checking out. His exhaust fab skills are sick!  . I sent you a PM with pics showing my same cowl and how it sits with longer (363mm) Fox Podium R shocks. Did that help any?

[BLAC]

Yes and thank you for the pics!  I was looking at the Kinetic kit, and think I can make it for a lot less than $700.  I have a mandrel bender, welder and access to some clevis joints.

I have been looking at theirs and the couple that Cliff has done.  In theory I could bang it out, but I dont know enough about suspension geometry to fee completely comfortable yet

[BLAC]

here is a quick and dirty photochop of my bike with a monoshock..

I think im going to go for it 

[Retro Rocket]

here is a quick and dirty photochop of my bike with a monoshock..

I think im going to go for it 

Yes, retaining the stock swingarm {length} and retaining the correct wheelbase/geometry is a smart move, there are lots of examples of how NOT to do it on the forum with bolted in monoshock swingarms from other more modern bikes, usually stretching the rear out 4/6 inches or more. Member Godfrey has a good example of what you plan, looks damn good too...

Check out Godffrey's bike...

[BLAC]

Thanks for the encouragement and info!

I have seen pretty much every cb550 with a monoshock on the Internet at this point 

My main question is regarding the angle of the shock, should that be in-line with the mounting point of the swing arm brace to the swing arm so it makes basically a straight line or can it angle downward at all from the top mount to the swing arm mount (if that makes any sense).... I will draw up what I mean in the AM

[BLAC]

Most of the (good) bikes that I've seen have an angle very similar to the frame tube at the rear of the main section. That allows for the most travel and damping. But, when you buy a shock, a good company will ask you the design criteria of: angle, weight, distance, bike, etc. to provide a unit that functions properly. Don't do this much work on your own then buy an off the shelf unit because its the correct length. It may well not be designed for an application like yours at all.

Totally agree.  I am most likely going to have RaceTech custom make a shock for this bike. 

[SOHC4 Cafe Racer Fan]

Most of the (good) bikes that I've seen have an angle very similar to the frame tube at the rear of the main section. That allows for the most travel and damping. But, when you buy a shock, a good company will ask you the design criteria of: angle, weight, distance, bike, etc. to provide a unit that functions properly. Don't do this much work on your own then buy an off the shelf unit because its the correct length. It may well not be designed for an application like yours at all.

Totally agree.  I am most likely going to have RaceTech custom make a shock for this bike.

Matt Wiley or one of his colleagues at RaceTech should be able to hook you up.  They are very competent suspension guys.

[Denver_Larry]

If I can put my 2 cents in here on your quick and dirty photoshop mockup:

Consider making the new hoop that runs over the tire (from the original shock mount locations) a bit snugger to the tire than you have shown.  And possible using a longer support tube from the swingarm pivot area.  These both will help with the geometry, as it is now you will have a falling rate setup instead of a mostly linear or rising rate setup.  Or get the front end of the shock lower...

[BLAC]

I have to commend you. Despite the multitude of folks who chase an aesthetic and don't give much through-thought, you on the other hand have mocked, photoshopped, analyzed, and now are prepared to have professionals perform the critical calculations. Its really great to see someone update these bikes "properly" and get what the want out of it. I doubt this will fall into the "Started, never finished" bin due to lack of commitment.

You will invest far more than the market for this bike will return. BUT, you will have a truly custom bike, that you built, that can be bought, no one else has, and it will still be a blast to own/operate and cheap to repair in 20 years. If I had a hat on, I'd remove it for you-

Thanks, cal I really appreciate it!  I figure that if I'm going to do it might as well do it right!  And there are people way smarter than I am, so might as well pick their brains.

If it's no fun to ride, I have wasted a lot of money 

[Retro Rocket]

I have to commend you. Despite the multitude of folks who chase an aesthetic and don't give much through-thought, you on the other hand have mocked, photoshopped, analyzed, and now are prepared to have professionals perform the critical calculations. Its really great to see someone update these bikes "properly" and get what the want out of it. I doubt this will fall into the "Started, never finished" bin due to lack of commitment.

+1
Thats the exact reason I commented here Cal, There's very few here that actually do it right when performing these type of mods   

[RAFster122s]

I'm looking at the photoshop mock up and if I think about the arc of travel for the swingarm would it translate into the motion needed?  It arcs forward and then down, right?  But, I haven't really looked at monoshocks, so, maybe I haven't considered it enough or studied them at all.  So, never mind.

I think that Godfrey's monoshock conversion would be worth looking at...  He has some very nice builds documented on his site.

[BLAC]

I'm back from the dead! It has been a few crazy months at work and I am just coming of 25 days straight on the road... The good news is I have made some more progress on the bike!

I bent a hoop out of 1" chromoly, and then decided to chop off and file down the stock mounting points from the swing arm and slot the "hoop bar" so it can sit recessed in there to look clean/stock once finished. 

Now on to the pics...

Milling the channels in the hoop.


Added the front brace bar (I'm finally getting decent at fish-mouthing!)


Test fitting... Getting Closer...


Ahh there it is.


Mock up.


Looking good for now!


The one thing I don't like about the lines of my bike is the Joker Machine brake strap.. Is there a way to remove that, rotate the drum a bit and mount the tab to the swing arm or the hoop bar I made (or any number of possible mount points)?

[540nova]

A hole saw makes fish mouths very accurate and easy. 

+1 it's what I always use. Tubing notchers are pretty inexpensive.



1974 CB450, 2006 CBR1000RR

[BLAC]

There must be a reason that the drum brace bar is so long and attached up at the front of the swing arm, is it to limit the twisting of the swing arm when heavy braking is applied?  Im just wondering why it isn't anchored to the swing arm much closer to the mounting point?

[luvmy71]

Just started reading your thread.  Great job!  I just started a 550 build (first build for me) from a frame and engine so this along with several other 550 threads and the input from the great members here are going to be extremely helpful.

Did I see an Oregon Ducks Fiesta Bowl t-shirt somewhere along the way?   Go Ducks!!!  Class of '81 when it was painful.

I live right down the 5 in San Diego.  Would love to connect with all the LA board members sometime when there is a fun event.

Keep up the good work!

Kevin