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Discussion Starter · #1 ·
Hey there guys i'm new but I've had this project cb750 for about a month and i was previously posting more on a cafe racer forum but since I've recently decided the original motor just isn't going to quench my thirst and i figured this project is officially falling more under the area of expertise that ill find here. Now the project itself...its an 82' cb750 and i'm putting an 06' R1 SE front and rear on the bike (the swingarm is going to end up being custom to avoid having the wheelbase of a bus) ill be fabing my own subframe and I've chopped a 75' cb750 tank to fit that i think looks pretty good. My main question is to anyone who has placed a modern sport bike power plant in an older bike or even an air-cooled bike... I owned an 03' cbr600rr and i loved the power curve and the fact that its a Honda doesn't hurt so I'm really leaning in that direction. I'm prepared to run pods and lose a little bit of power and obviously some frame fabricating will be in order... what nightmarish task might await me that I'm over looking... thanks.
 

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UnicycleMode
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Quite a few have taken the task on. Kind of curious about the way you find solutions for this swap. I'll still say kawabusa is the direction that you should look for inspiration for induction solutions. ;)
 

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The Hell You Say!!
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5" is pretty low...I would be shooting for at least 8-9'' before exhaust. Any normal 4-1 pipe and you are going to lose about 3''. Can you move your suspension set up a couple of inches??

Other than that I cant wait to see an update.
 

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Discussion Starter · #7 ·
5" from the bottom of the frame tube? How far below that will your exhaust hang?

Sorry if I'm coming across as negative. I just ran in to these issues before. But I'm sure you know what your doing. , so I'm just gonna chill and enjoy the show. :)
I haven't done the exact numbers but when i start chopping on the frame my plan of attack is to rebuild and reroute the top tubes to "cradle" the engine more and i intend to steepen the head angle to match the R1 a bit closer and give me closer to the desired trail...this should give me a bit more ground clearance and better handling and when you factor in the fact that I'm building my own swingarm to the required height i think it will be okay... if its not then it isn't like I'm not already chopping and cutting so ill just do what must be done... its definitely a valid concern. Just had a baby girl (uh oh) 1 1/2 weeks ago so for now its a slow project but it will definitely pick up speed soon enough. Waiting on a back ordered pipe bender and notcher at the moment and the fun will really begin!
 

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Discussion Starter · #8 ·
...and by all means, please anyone feel free to point out these kinds of issues. I've built a couple resto mod cars/motors and I'm an experienced fabricator but this is more or less my dive into the motorcycle fab world. I've owned a couple but never taken on a project bike like this so don't hold back.
 

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You can get a stepped top clamp to slide the forks down a bit (well, I know they make them for Busa fronts to fit to GSX14's).

Biggest problem you're going to find with putting a modern motor in that chassis is the intakes point to the sky and you've got a backbone frame in the way. Maybe a Z1000 motor or ZRX would be a better choice as the intake tracts are closer to horizontal.
 

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Is my bike ok?
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Congrats on the little one!

These bikes just had long legs in stock form. Then dropping from a 19" tire to a 17" with a low sidewall aspect ratio makes it even worse. But it sounds like you know what you're doing. Pulling the rake in is a great idea. The head angles on these old standards was pretty lazy.

F2 & F3 forks work really well on these bikes as far as height and tree offset with all other things being stock, but I'm sure you're not interested in running 20 year old conventional forks :D

DW!
 

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Discussion Starter · #14 ·
Yeah I'm pretty set on the 600rr motor just because its about the hp im looking for, id like to keep in in the honda family, id like to keep to in the 03-14 years/technology range and they typically go on ebay for a price i like. I'm actually trying to find the dimensions on the motor height etc so i can determine just how difficult it will be to fit up a custom air box or pods with an elbow fitting... I'm open to other motors but i want to see if i can do the 600rr first then work from there. I'm wanting to alter the backbone on the frame to cradle the motor and give me some more room up top similar to the modern sport bike frames and that means ill have to alter the tank again but oh well. If anyone has access to an 03-12 motor and wants to shoot me some general measurements i would appreciate it... otherwise ill probably be creeping around dealerships looking for a used bike to measure on before i decide for certain.
 

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Discussion Starter · #15 ·
You can get a stepped top clamp to slide the forks down a bit (well, I know they make them for Busa fronts to fit to GSX14's).

Biggest problem you're going to find with putting a modern motor in that chassis is the intakes point to the sky and you've got a backbone frame in the way. Maybe a Z1000 motor or ZRX would be a better choice as the intake tracts are closer to horizontal.
Good idea, cognito moto make a conversion stem for the R1 to cb750 and I'm hoping it will fit so i dont have to have a custom triple machined, but if i can do a stepped top clamp made for the R1 then i will definitely go that route...or I'll just pay a zillion times as much and have one made...still searching for a good machine shop with a good rep here in San Antonio since ill inevitably need one.
 
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I like it, thinking outside the box is always good :)

I think the intake & tank fitment are going to be your main issues with fitting the motor & there maybe a problem squeezing the rad in if you shorten the rake too much, its probably going to be tight anyway at a guess

I look forward to seeing where you got with this
 

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Discussion Starter · #17 ·
Okay so i found some good CAD models and an amazing resource. http://www.wwufsae.com/Shared_FSAE_CAD_Library/

Its a collection of fsae cad models and the motor selection is vast and is broken down to air filter model and all individual parts etc... great public resource for anyone building motors. I'm going to compare some measurements after work and get a general idea of how to proceed.
 

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Discussion Starter · #18 ·
Okay i think i can squeeze the 600 motor in there, its gonna take some trickery but i'm not in an hurry and i got time to screw up and re-do (only a couple times hopefully). I'm going to throw together a rendering and ill put it up when i get somewhere. There might not be too much "cb" left on the bike when i get finished but that doesn't matter to me much.
 

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Discussion Starter · #20 ·
A drawing i threw together but its just a starting point. I'm going to practice a little pipe bending and notching for now and keep mulling it over. I'm going to try and work out a frame to where i can keep more of the original cb750 but still cradle the motor as a stressed member...and without adding 40lbs of metal... if anyone has frame references or pics i would love to see some good ideas. I know people have done builds similar but i seem to be having a hard time finding much variety or detail on said limited variety of pics/builds. The "cafe" style one is just an idea from when i was still planning to leave the rebuilt 750 in it.
 

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