the frame can't nearly handle the power that engine is putting down
This is a discussion on Planning a new project. A vintage bike with a modern engine within the Project Builds forums, part of the Caferacer.net Forums category; Hey so I'm planning on doing a build, partly as a school project, partly because I've wanted to for a while now. So I am ...
Hey so I'm planning on doing a build, partly as a school project, partly because I've wanted to for a while now.
So I am planning on taking an older model bike such as a Honda CB750 and swap the motor for something like a CBR600RR or R6 engine and put newer suspension on it. I may have a line on a R6 (I believe it's a 2000) through my internship @ Capitol Yamaha as a donor bike for the engine and suspension.
Any tips or advice would be greatly appreciated. Thank you.
do you have any advice on how i can make it work? This is something that I have been wanting to do for quite some time now. In my mind its the next evolution of cafe racers, because they started by doing engine swaps and dropping weight. Thank you.
There is a huge difference between a slow heavy CB750 motor and say an R6. To put that in perspective, the fastest CB750 motor would struggle to make 100HP and any R6 makes that out of the box with horses to spare. They are generations apart.
For sure we used to swap one heavy underpowered motor for another heavy and slightly less underpowered motor, but we are talking generational differences here. Compare a light rigid R6 frame and swingarm with an old flexy CB750 and there just is no comparison in terms of stiffness and geometry is very different as a result of that.
You could take a crashed R6 and strap its powerplant in a jig with stock R6 suspension and brakes and build a trellis frame around those parts using a CB750 steering head and pretend that the frame is more or less stock CB750 but there's not a lot of point.
So teh question here is what is the next fashion trend? It might be naked fighters in more of a cafe race look or maybe Street fighters or an updated AMA superbike look, but I don't think so. Cafe racers embody the spirit of the sixties and seventies - not very fast but they feel fast and are basic motorcycles. AMA superbikes were the next generation of racers and bikes like the ELR copied that look a little way down the track.
I'd suggest maybe a modern single cylinder motor and suspension in an old school frame. Is there such a thing as a modern single? Well maybe not so many, so that leaves twins - perhaps a HD in a Cafe race looking chassis or maybe the Virago will be redeemed and will rise as the next gen cafe racer.
Probably naked Kawasaki or Honda 300's are the next big thing - looking like Moto3 race track refugees with echos of teh past in the styling.
Maybe it's early FZR and CBRs made to look like Moto2 or MotoGP bikes.
I understand the appeal of using a more modern motor, suspension, brakes and electrics in an older chassis because you could increase the reliability and more riding versus less wrenching time. The problem is, as has been pointed out, the frame can't handle the HP and the suspension loads. So, the trick is to brace the frame so it will handle more suspension loads, stay away from big tires, huge brakes and USD forks. Finally stay away from high HP new motors. For an upgraded CB750, I would look at the first generation CBR600F motor, front suspension, brakes and wheels. Brace the CB750 swing arm or find a period replacement. Keep the twin shocks and transfer the entire electrical system. The CBR had about 80 RWHP, 37mm forks, a 110 -17 front tire and a 140 or 150 -17 rear. With the 750 frame and bodywork it would still be heavy and not great handling but it would be good. You can find a complete CBR600F for under $1000.
If you work at a Yamaha dealer then an FZR600 would work just as well, although it has a few more HP. A Seca II aircooled would work and has about 60HP (claimed 70 at the crank)
AHRMA not anymore
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Alright. Thanks everyone, maybe I'll just build up a racer without swapping the engine. You certainly gave me a lot to think about, and you know more than I do so your advice means a lot.
That being said, if you have an idea on how I can do the swap, let me know as i have been thinking of this for over a year now. Just keep in mind that my resources and budget are fairly limited as I', only 17.
Would it be any easier/more feasable with a KZ1000?
Last edited by sethh; 01-25-2015 at 01:48 AM.
get a cbr600, or an fzr600, or something like that, and make it look like an old shitbox. actually, the honda hornet had a spine frame with everything else modern. get a 900 hornet and fit an old tank to it.
You are thinking about this like people think about cars and engine swaps. You can't do that with a motorcycle because as has been mentioned the engine and frame are structurally tied together.
As as you are 17, I am going to assume you do not have a motorcycle license or riding expirence. Instead of a project, how about you go and get those instead. But a bike, a running riding one, and get a license, and then use the bike to get around for two years wile fixing and maintaining the bike yourself.
Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
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KZ1000s are some of the most ill handling bikes, unless you do a lot of CAREFUL work bracing them.
It's just as pointless to put a modern engine in one of those than it is to do it to a CB frame.
You'd be amazed at what you can do with a 70s Triumph with some modest suspension upgrades and good tires. They are more than an average rider can handle on a track. I have a hard enough time with my late 60s 650 Triumph, we're about equally matched. On a modern bike, I'm no slouch. Ever ridden a Kawasaki ZRX? I've had 3 of them; a 1200 in my garage right now. It's what the KZ would have naturally progressed to, but they made a quantum leap and covered everything in perimeter frames and plastic instead. It was smart of Kawasaki to take a step back the way they did.
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if you're on a limited budget, go try to set up your cb750 with good suspension and tires, I bet you'll shoot your budget to shit before you can even touch a cutoff wheel. I think some of the psychology of projects like that is that you have a subconscious fear of failure, so you propose a project so ungodly complex and expensive, that you'll never have to come close to completion and potential failure, "it always works great before you ride it!". so start smaller, fail a lot, learn a lot, really crazy projects are successfully completed as an evolution rather than a ground up "never seen asphalt until it was all the way done" deal
Last edited by roccitycafe; 01-25-2015 at 09:31 AM.