Topic: Starting the CBR fork / swingarm conversion *Updated*

[ScottB]

After a few months of putting parts together I am ready to get moving on this.  I know some purists won't be too excited, but hey, I think this is going to be sweet.  I picked up a CBR 900 front end, CBR 600 swing arm and CBR 600 wheels. I found an extra stem that I am having swapped out for the 900 lower, that should be done next week.  Here is a pic of the bike when I recieved it:



I painted it, chopped the fender, drag bars, and a tune.  I ended with this:








Here are some of the parts:





Now I just need an ugly tail section...

[Triffecpa]

I did a similar project with a '78 750F, only I used Kawasaki ZX-6 parts (forks, wheels and brakes) from an early 90's donor bike.  The Kawasaki swap was trickier than using Honda parts though as I had to have a custom steering stem turned to mate the ZX-6 triple clamps to the Honda frame.  I also used a Cal-Fab swingarm for the CB750F at the rear.  Anyway, I think that it was a cool project.  Good luck with yours.

Tracy

[KB02]

Keep the pics and progress coming. The front end of my K8 will end up going away and being replaced with something else. Not sure what, yet...

[ScottB]

Thanks guys.  I got a late night itch to dig my self a little deeper:




The CBR swingarm measures roughly 4 inches longer than the stock one.

[azuredesign]

It looks like the swing-arm will increase your wheel base, is the idea for using it to get the bike to track more directionally at speed? I wonder if the Seeley and other aftermarket frames had a longer wheelbase, and perhaps a but less acute steering stem angle to track easier at speed. I don't think roadracers back in the day found having to muscle bikes through corners that much of a challenge, as long as the bike tracked stabily and predictably.

Thanks and all best,
Ben

[ScottB]

Ben,

I have more than a few reasons for doing the swap.  The first is that I am 6'4 250lbs.  The bike doesn't seem to be very stable with me at freeway speeds.  I'm hoping that with the extended swingarm, larger front tires and better suspension it will track a bit better. 

The other reasons are aesthetic .  I have seen a few F bikes on the forum that have done the swap and they look amazing.  I'm pushing for the same result.

[KB02]

Are you going to use the Mono shock or stay with the stock Duals?

[azuredesign]

Scott,

Those both sound like good reasons. Are you going to use the wheels in the photo as well? I think they look great, and may add some stability as well. You also may want to consider a steering damper to further enhance the stability, if needed.

All best and put up photos when you get done!
Ben

[ScottB]

Azure,

I will be using the wheels in the picture albeit they will be black by the time they go on.  After all the bugs are shaken out I will get a set of wire wheels with a black rims on her. 

Off to the machine shop tomorrow to have new bushings made.  Anyone viewing happen to have the exact spec's I need?







 

[dusterdude]

scott,im going to be doing the same deal on the swingarm in a few months.are you going to drill the frame for the larger swingarm bolt or make bushings for the swingarm so you can use the stock bolt.i am very interested in hearing about your experience with this,please keep me posted.

[ScottB]

Duster,

I dropped off the bearings, swingarm and lower forks this morning to my machinist.  Having new bushings made was going to cost around $300 because of the hardend steel issue.  We tentatively decided that the best idea so far was to use the factory hardened steel CBR bushings, grind them down for clearance and machine a smaller bushing to fit inside the CBR one but over the CB swingarm bolt.

I was nervous about blowing holes in the thin walled swingarm so I am having him fab up the shock mounts too. I will save my nonexistent welding skills for mounting the rearset brackets.

I can't wait to get the parts home and see this thing go together, glad to see there are others interested in this too.   

[dusterdude]

oh yea,very interested.i think im goin to try to make some bushings that go into the cbr bearings,according to my very rough measurements,the shocks will land on top of the swingarm,if thats the case,im going to weld blocks on top to accept the bottome of the shock.

[Tim2005]

It looks like the swing-arm will increase your wheel base, is the idea for using it to get the bike to track more directionally at speed? I wonder if the Seeley and other aftermarket frames had a longer wheelbase, and perhaps a but less acute steering stem angle to track easier at speed. I don't think roadracers back in the day found having to muscle bikes through corners that much of a challenge, as long as the bike tracked stabily and predictably.

Thanks and all best,
Ben

The Seeley chassis has a shorter wheelbase than the stocker, by about an inch, achieved by shortening the swingarm and/or it's mounting position. The rest of the geometry is stock +/- 1 degree rake. Not sure about other aftermarket frames' specs.

Cheers

[cben750f0]

looks like a great project mate, looking forward to some more pics...

peace

[seaweb11]

I also look forward to seeing more of this thread.   I like the way you started, your attitude, and your obviously great relationship with your machine shop.  Dive in and give-er    The way you are describing it, this could become "The" how to thread.

Make notes, we all may be asking questions later if you don't key in all the specs.............

Your like a kid waiting to open is B day present......."a NEW shiny swing arm"     

[ScottB]

Finally got the stem back from my machinist.  Looks awesome. I will have to wait until tomorrow afternoon to get the swingarm but from what I saw today he is very close.  It seems like the "bushing in a bushing"  idea worked out well, I'll post pic's when I get the actual parts.

As DougID once said "I just try and get one thing done a day".

Here is the new hybrid lower and stem:



The new upper waiting on paint:

[cben750f0]

looking great M8, cant wait to see how it all goes to gether....

peace

[Wycked]

  The first is that I am 6'4 250lbs.  The bike doesn't seem to be very stable with me at freeway speeds.

Not knocking what your doing, I think its brilliant!

But having said that, I want to address this comment, How well does your normal riding jacket fit? Tight? Snug? or Loose? A stability issue that people often think is the bike, turns out to often be caused by the fit of their jacket and how much the wind pulls at the material of their sleeves, which then makes the bars quiver, which makes the bike feel unstable. If your jacket Balloons up around you at speed, it too can have the same effect. Just some food for thought, I would really hate for you to go all through this and find out the bike is still just as unstable as before you started.

Keep up the good work, it will look incredible when your done!

[ScottB]

Wycked,

Thanks for the comments and I hear what you are saying about loose fitting jackets; my spidi is snug as a rug.    My previous R1 and other liter bikes I have ridden have felt more "solid".  Being this is my first vintage bike that I have brought up to freeway speeds, I was tempted to blame any instability on it being either a) and old bike or b) my big ass.

Even if nothing changes in the handling characteristics I won't really mind.  I imagine I am not alone in seeing the artwork and beauty of these bikes, especially one I have been so hands on with.  I wonder if I can convince my wife that it would make a great conversation piece in the living room... 

[ScottB]

Big day.  HUGE.  I was able to get the rest of my parts.  Took a half day and got to work.

Here is the swingarm when I received it back:




Close up of the welds:




The picture is awful but you can faintly see the inner bushing pressed in there:



Other side and after I ground down tabs that are unneeded:



Time for paint!



While the paint was drying I started to assemble the front end:

[ScottB]

I removed the center stand:





I couldn't wait to get see the mock up on the ground so here it is!





The jack stand is only a preventive measure, it's not actually holding it up.  This thing is long and the stance is low.  Now comes the laundry list of small things to put together.  Anyone have ideas on who makes 45mm headlight ears?

[cben750f0]

Mate just wanted to chime in and say...bloody well done, looks awesome... about the headlight ears.... ebay.... i am sure there has to be some on there some where... would the headlight ears of a CB600 hornet fit?

NEway keep up the great work, and make sure you put more pics up

peace

[PhilaStandard]

When you're done please post a step by step procedure. A lot of guys would love to do this mod.


Does a 600rr Front end work for this?

[DCopp]

where's the rotors???

[750essess]

Just finished the front conversion myself, let me know if I can help in anyway. I will be doing the swingarm this winter, so I will be watching your progress for tips. 
A 600rr fork will work, but they are upside down units and will give you even less steering lock than the normal style. They are also more expensive to purchase used.