1979 cb750 build! Another DOHC

S

screwdriver

New Member
i picked up a 79 cb750 a few months back and have been slowly chipping away at the build

this is what it looked like when i got it


after i got her on the table


starting to mock up the new rear hoop and shock mounts


starting to cut


just ordered a seat from Glass From the Past. waiting on that before i get too crazy with the cut off wheel. figured i should have the seat pan in order to shock mounts and seat height and length right.

ive got 2 motors and 4 sets of cv carbs for this thing. both of the motors are in "unknown" condition. i was told they run......... but who knows. im not going to use the carbs (if anyone needs any let me know). im thinking cr-29's!
new top triple and clip-ons from DCC showed up. going to order some rear sets and fab up a mount for them.
i really like the idea of doing a key-less ignition system, couple of relays under the seat and a push button start in the steering stem. ;D
i found a set of lace wheels that are going to get powder coated black with stainless spokes.

I'll post more as I make more progress
 
i was out in the garage tonight trying to get an idea for where the tank/seat is going to end up at.



im wondering if i should drop the front of the tank an inch or two??? that would lower my stand over height. right now its about 31-32 inches. that seems a little tall to me...???... thats the seat height of my track bike.
anyone have any thoughts?
 
Leave the tank as is, lowering it is a bitch and a half. Make as thin a seat as comfortable, push the forks up 1.5" through the triples and mount your rear-sets about 2" up on the backside of the triangle. Hehehe, just a suggestion, I had mine set that exact way and it handled like a dream.
 
thanks man. thats good to know.
i was just getting ready to order some rear sets and try to figure out where to put them. thanks for the tip!
 
Jewbacca said:
Leave the tank as is, lowering it is a bitch and a half. Make as thin a seat as comfortable, push the forks up 1.5" through the triples and mount your rear-sets about 2" up on the backside of the triangle. Hehehe, just a suggestion, I had mine set that exact way and it handled like a dream.
Click to expand...

you could then use the extra 1.5" to mount clipons.
 


i got the new seat pan from Glass From the Past and the rear frame mocked up. going to need a little more tweaking before i weld it will up.
 
ok back end is tacked together.. new top triple and clip ons are installed. fab'ed up a seat pan and a tank mount today. tomorrow we tackle the rear suspension and the rear sets and maybe the seat mount if i can figure out how i wanna do it! :eek: :eek:



 
I'm in for this one.

I like the tank and seat fit and IMHO I would put the clip on below the yoke and lower the fork internally you will get 40mm easily without any issues and its easy to do and will give a cleaner look.

I'm no expert welder and others more qualified may comment. I dont think its a good idea to joint the seat rail like you have, I was told welding across a tube is a no no, the welds should run parallel with the the tube. Probably more like the flattened tube joint of the original seat rail. Also the support from the swing arm pivot to seat rail look to thin to take the force of the shock but that may be an optical illusion.
 
I wanna tag along as well! ;D Love the work so far.
Curious as to what was wrong with the bumstop seat that came on it?
Might suggest joining http://honda-cb750-s.456789.n3.nabble.com/ great bunch over there, much nicer than another CB750 forum that is out there. Kinda new so there isn't a ton of members yet but growing leaps and bounds.
 
the seat hoop is not welded across the tube. i used a gusset on each side to support the front of the hoop. as for the rear supports they are 1" tube, same size as the original.
you mean put the clip ons below the top triple? thats how i have them now.
i didn't like the idea that i had to pay someone a ridiculous amount of money for a seat made for this bike. i wanted to be able to run any seat i wanted. plus i wanted to get away from that cruiser look. flatten the tank out and match the seat to it. i wanted it in a straight line.

thanks for the ideas!
 
screwdriver said:
the seat hoop is not welded across the tube. i used a gusset on each side to support the front of the hoop. as for the rear supports they are 1" tube, same size as the original.
you mean put the clip ons below the top triple? thats how i have them now.
i didn't like the idea that i had to pay someone a ridiculous amount of money for a seat made for this bike. i wanted to be able to run any seat i wanted. plus i wanted to get away from that cruiser look. flatten the tank out and match the seat to it. i wanted it in a straight line.

thanks for the ideas!
Click to expand...

Yes the clipons below the top clamp. I was saying shorten them internally so you dont have to have them stuck up through the top of the top clamp. Unless you like it like that.
It was difficult to see on the photo how you had the seat tubes attached. Now I have a closer look I can see what you did.
Its a good idea to straighten out that seat tube area, makes it flow with the tank better and gives you more options on seating.

Whilst you are doing these frame changes have you considered bracing the engine cradle so it doesn't flex as much and improve the handling.
 
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