1979 CB750F Tracker (maybe?)

KPSguy

Member
jordandogtown said:
I took a few minutes to work on a (very) rough mockup for the subframe rails. I'll be attaching them in the same manner as the stock, and adding in a few more gussets, so I think they'll be plenty strong enough. Tubing is 1" x 0.125" - same diameter as the frame but a lot thicker. I have a tendency to overbuild, but the rails will be hidden by the seat anyway.

I want to give the bike an extremely slight "stinkbug" stance, with the rear just barely higher than the front. Right now, the bottom frame rail is 2.5o in relation to the table top. This mock up has the new sub frame at the same angle. I'm hoping if I get the frame in the right places, I can adjust the suspension to fine tune the stance



I had to get a sense of the bike with the wheel and seat in place, although this is a pretty pitiful attempt. The bottom of the seat pan will sit on top of the subframe rails, so it's about 1.25" higher than it should be, and needs to be trimmed at the white line, and who knows if the wheel is where it should be - but it was fun and definitely got my wheels turning



Note: a bike on a table is so much better than a bike on the floor. I've been missing out
Man that's a great project you going. Looking forward to watching your build progress, and what ideas you come up with. Nice looking tail tail section.
That table your working on ...man I need that. Work on ground level kicks your butt for sure.
I've got a 78 " 750 F 3 in the shed just waiting for the right motivation to start.

I'm just toying around with a 82. CB 650 SC " Nighthawk " barn find for my winter project..about a 1000 miles on it. Was too nice to Cafe out or Brat .



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KPSguy

Member
VintageMBike said:
Yeah.

The guy over there, Buzz, asked me what my setup was. They jetted the carbs and sent them to me. Slapped them on and had zero problems. They know what they are doing over there!!

Here is a link:

http://dynoman.net/carb/keiCR.html#cr31
Yeah man , Buzz does it the best. I agree!

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enterlance

New Member
jordandogtown said:
Thanks for the heads up, I hadn't really shopped around much yet.

Do they come with the same plastic velocity stacks that are included from DCC? Ready to bolt on (other than any jetting changes)?
I got them from webike. It's a Japan seller. I got the CR carb (JB Power Special).
 

jordandogtown

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After my short polar vortex hibernation, I managed to find some time to start cutting/grinding/more cutting some steel.

I'm a woodworker by trade, and admittedly have very little experience in real metal fab work. But I try to step up every project and learn something new, and this time it's tube notching. I don't have any reason to spend a ton of money on a real tube notcher for how often I'd use it, so I tried to make due with what I already had.

A porter cable drill press, small vise, and a cheap hole saw:



The cuts pictured were actually numbers 3 and 4. I had the drill press set to 390 RPM and with plenty of patience and oil I was pleasantly surprised with how well it performed.
(I went back and filed the ends to a flush fit around the frame rails, just no photo)



Then shortly later I found the life span of this particular hole saw. Oh well, everything is notched other than the 1/2" support pieces which I can do by hand. $7 well spent

 

jordandogtown

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For the top rails, I used my trusty $20 angle grinder (still waiting for it to die to upgrade) and rough cut a shape that mimicked the original Honda subframe. Instead of cutting, Honda pinched the ends of the subframe to mate against the top of the frame. I'm not a real strong pincher and these rails are twice as thick so I decided to cut.

I'm happy with the idea, but will need to file/grind them to dial in the angles I'm looking for. 3/16" gussets will also be added in the corners for piece of mind.





And I couldn't resist another mockup. While still not exact, this one is a lot closer than the one a few posts back. The seat will be trimmed at the white line (I think), and it will have much lower tracker style bars. I'm really digging the stance so far.

 

adventurco

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Nice work notching the pipes, something I've yet to mess with. Visually the seat position looks much better. For some reason my eye wants it to be a hair lower still, though. I also like the tail section longer rather than cut off at your line, but thats just my .02
 

The Jimbonaut

Well-Known Member
Looking great man, really like that stance. Me, I like the white-line-chop, it'll take some visual weight off the rear end. Nice job notching the frame tubes too
 

jordandogtown

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Thanks guys. The rear end will probably end up being a tad lower since it's still not supporting it's own weight back there. But I am looking for a slight stinkbug stance over a parallel line to the ground.

I'm really conflicted about the seat (why I haven't chopped it yet). In person, it looks huge, and really weighs down the rear visually. But in photos it looks totally different and almost starts to suit the bike. My eyes are definitely playing tricks on me, so I'm trying to wait until everything is at least tacked together before I start hacking away. Metal is much easier to stick back together than fiberglass.

An angle where the seat looks too big, IMO. I'm shooting for more of a minimal flat track style than a full café cowl
 

pidjones

Well-Known Member
Upholstry will change the seat appearance. You might go ahead and get that made up or at least simulated to "guide the eye". Don't worry about making it look like a flat-tracker. You are too far off in so many other ways, just make it something you like.
 

jordandogtown

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pidjones said:
Upholstry will change the seat appearance. You might go ahead and get that made up or at least simulated to "guide the eye". Don't worry about making it look like a flat-tracker. You are too far off in so many other ways, just make it something you like.
Right on. That's been my motto the entire time lol if it ends up "flat track inspired" I'll be happy, if by nothing else than the paint job.
 

jordandogtown

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I don't own a computer so for photo-copping I'm reduced to Microsoft Paint on my lunch break. I know I'm getting the cart in front of the horse here but I've had so many paint schemes bouncing around in my head I had to start sketching them out. This one is the front runner so far, taking cues from the CB1100F and Honda's early flat track days

Tip: squint your eyes and take a few steps back and it's not so bad :D
 

The Jimbonaut

Well-Known Member
Well that looks great. Love the paint, and the trimmed cowl looks the business. Upvote from me 8)

By the way, how you planning on uniting the seat pan and the tank? It looks like a couple oft tricky angles there to marry in a coherent way?
 

jordandogtown

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The Jimbonaut said:
Well that looks great. Love the paint, and the trimmed cowl looks the business. Upvote from me 8)

By the way, how you planning on uniting the seat pan and the tank? It looks like a couple oft tricky angles there to marry in a coherent way?
Thanks Jim. The top of the seat pan should meet the bottom of the tank evenly, but the bottom of the seat pan is where I'll have some trim work to do. I'm thinking of some sort of expanded metal/mesh/number plate/acrylic/carbon fiber piece to tie it altogether. The subframe brace (not pictured) should provide some more real estate to work with

(so to answer your question, no, I don't have a plan at all ;D)
 

irk miller

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It's a good look, though the plywood strips won't work. At least not ply that thin.
 

jordandogtown

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irk miller said:
It's a good look, though the plywood strips won't work. At least not ply that thin.
Don't worry. Everything will be reinforced with the straightest 2x4s Lowes has to offer
 

irk miller

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You might want to check how you're running that rear shock. In stock trim, the CBR shock runs at a significantly smaller angle, which is going to make your setup act totally differently. There's also the possibly of binding which will could bend or break the shaft. I'd like to think it won't be that extreme, but I've witnessed it happen to another guy riding in front of me.
 
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