Race bike build

F

fastbroshi

Active Member
Didn't see a section for racers, figured this was as good as any. My current project is a '78 CB550F I'm converting to a race bike. Here she is disassembled down to the frame.



I plan on gusseting the frame and adding brackets to the CBR swinger for dual shocks, I'm not messing with a monoshock. Front end will be 1999-2002 Yamaha R6. Motor will be basically stock with some mods, I'll get into those as this comes together. If anyone happens to have a copy of Tony Foale's suspension program let me know. Here's some more pics for now. I'm not sure how to work out this rear end geometry.






Gussets I plan to add:








I'll add some more later, I've already trimmed off almost all the brackets it's going to lose.
 
Nice start man, although did you intend to put the 'I taste good' picture in there? ;D

Should be a blast to take around the track, I'd love to do a similar build for the Post Classic races down here. What other mods do you have in the pipeline?

Cheers - boingk
 
boingk said:
Nice start man, although did you intend to put the 'I taste good' picture in there? ;D
Click to expand...

You bet I did. Those are the main mods I listed up top, the rest will just be details. Oh alright let's see a 650 cam, ported polished head, don't know about the exhaust just yet. Looking for a Yoshimura header but everyone that has one won't give it up for the cause. Going to use the mags from the R6 and CBR, so there'll definitely be some more traction available. This is the main reason for the frame gusseting.
One main thing I don't know about yet is what shocks to use and what length they need to be. I have no idea what angle they'll need to be and such. I want to make sure and get it right so I don't get bucked off, so some research is in order.
Looking to race it in the vintage open classes.
 
Hi, can't tell from your posting where you're located, but wondering what racing organization(s) you were hoping to race with - VRRA, AHMRA, WERA, AMA, whatever?
For example, the mods you are making make it inelegible for the VRRA, though you might have a damned fine bike for track days - where as long as the bike passes safety inspection, you're good to go...
The VRRA Tech people are extremely good and if you download their rulebook and follow it to a "T" - and email them when you have any questions, then you shouldn't have any problems during tech inspection. It'd be a shame to spend a ton of time and $$$$ and have the bike sit on the trailer, or in a corner of the garage...
Regarding optimum mounting angle for dual shocks to get maximum rise rate, email me at pacomotorstuff@cogeco.ca and I'll see if I can find my old S&W Shocks book to scan some info and send to you.
Regards,
Pat Cowan,
Pacomotorstuff
 
Although gusseting is an improvement on way or another, placing them right inline with the center of the tube is the weakest way to do it. Typically they would run from tangent to tangent. With the way the ones pictured are placed the tubes can allow movement by deforming/ovaling.
 
youll have a beautiful track day bike when done... but i cant see it being legal for any vintage class... maybe a newer class? in a vintage class your out... in a new class, you wont be very competitive (sorry to say, but the guys who start with a new motor just have a step up on 30+ year old technology).


still looks like a great build though... ill be following this one
 
I am not that familar with the cb550 but, one thing I noticed with using a more modern swingarm on a vintage bike, especially one that was from a monoshock bike is that they are way to long. I would check on what your wheel base is going to end up at with that swinger, your probably going to find that it is more in line with a sport/tourer or even a cruiser. If this is the case, and you use that swinger, you might want to consider just racing it at the dragstrip. ::)
 
mysta2 said:
Although gusseting is an improvement on way or another, placing them right inline with the center of the tube is the weakest way to do it. Typically they would run from tangent to tangent. With the way the ones pictured are placed the tubes can allow movement by deforming/ovaling.
Click to expand...

I'm not an engineer or geometry major, but from what I've read they shouldn't be attached to the tubes perpendicular, rather overlapping the tube somewhat. I'm following you. Given these welds may not be perfect, but they give me a good reference for location. Thanks for the input.
 
Rocan said:
youll have a beautiful track day bike when done... but i cant see it being legal for any vintage class... maybe a newer class? in a vintage class your out... in a new class, you wont be very competitive (sorry to say, but the guys who start with a new motor just have a step up on 30+ year old technology).


still looks like a great build though... ill be following this one
Click to expand...

Nope it's legal, according to this wording for the Superbike Classic designation (from http://www.cmraracing.com/pdf/2010/Rulebook/CMRA_2010_Rule_Book.pdf):

Machines intended for use on public roads in their origins with more than 1000
units available worldwide may be changed or modified, to any degree, with the following
restrictions:
a) In Superbike the original combination of frame and motor must be maintained
except in the case of similar models with directly interchangeable engines. Single cylinder
machines may use any engine, frame, and fairing combination.
b) Grand Prix 2-stroke machines will only be allowed in A & B Superbike.
c) No reduction in OEM displacement is allowed for the purpose of meeting the
displacement limits of a lower class.

The superbike classes break down by displacement, so no worries there either.

And about the wheelbase - it's about a 2.5" gain, so that would put me at 57.8". Right around VFR specs. And VFR's can boogie in case you've never ridden one. It will be tad long I agree. With my rake and trail taking the r6 forks into account it should be fine.
 
Pics taken a couple of days ago, almost done trimming. Been busy stripping a couple sets of spare forks.

IMG_0169.jpg

IMG_0170.jpg

IMG_0171.jpg
 
Cool i'm glad to see that your bike will be legal. I'm watching. I dont totally understand the comment about the gussets. Does he mean they should not be welded in the center of the tubes and on the edge of the tubes instead? Keep it up.
 
thompsonmx100 said:
Cool i'm glad to see that your bike will be legal. I'm watching. I dont totally understand the comment about the gussets. Does he mean they should not be welded in the center of the tubes and on the edge of the tubes instead? Keep it up.
Click to expand...

He's saying the gussets in my example are less than optimal because they aren't placed right on the tubes. Compare those to this example:

GussetEx1.gif


The good examples here are on the outside of the tube, instead of being more onthe inside. See how these have a curvature to them as well? Read more about it here. This guy is like Stephen Hawking's brother or something he's so damn smart.

http://www.tonyfoale.com/
 
If length is the only problem for the swinger, hell, that is an easy fix on the CBR swinger! You could cut, and weld shorter, been done a thousand times on hundreds of bikes so don't give me any "its too week for racing" bull shit! But if you don't want to go that route, would not be too hard to just cut it off and re-cut the holes!
 
Just did some quick measurements, if the CBR swingarm were cut down to the 550 swingarm length, the CBR arm wouldn't have enough clearance for the wheel because of the shock bracing. And no I'm not cutting it out.
 
fastbroshi said:
Just did some quick measurements, if the CBR swingarm were cut down to the 550 swingarm length, the CBR arm wouldn't have enough clearance for the wheel because of the shock bracing. And no I'm not cutting it out.
Click to expand...

Yeah, thats the problem with mono shock swingers. Also they tend to taper in pretty quickly at the shock mount, so if you were to cut it out and relocate it, you have to watch your clearance and what size tire you are running. I still say that 57.8 is way to long a wheelbse for a track only bike.
 
Yeah that seems to be the consensus from people I'm talking to. I think I'm just going to make sure the stock one is setup with new bushes and my shocks are top notch.
 
thompsonmx100 said:
Add a brace to it. Wouldn't be hard to do. Just bend a loop and weld it up.
Click to expand...

Beleive it or not the stock arm is up to snuff. I've talked to some really good racers that specifically race this bike and they say it's not needed. Besides, it's just extra weight. I've seen some done before though, looks pretty cool.
 
a lot of the flex racers feel in the back of the bike is from the swingarm, not the frame as many think. brace it. its added weight, but will benefit in the long run.
 
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