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Author Topic: FRANKENHONDA II the 1982 DOHC CB 750F2 Build  (Read 19644 times)

Offline cb250nproject

  • Posts: 190
  • If you can make it better do so
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #20 on: Jun 13, 2017, 05:07:23 »
so I'm mucking around with the tail part of the bike trying to get a rough idea of how it's all going to come together.
I've decided to add small side fairings to kind of finish it off... you're going to have to imagine it connects with the tail section and covers over the rear hoop...
It just looks kind of unfinished without the side fairing.

Although I've got all the gear to fibreglass it up I think I need to do a little more r & d on how best to incorporate the side fairings and also how the fairing is going to marry to the frame.




Sent from my iPhone using DO THE TON
first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline LightsOut

  • Posts: 36
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #21 on: Jun 14, 2017, 08:15:54 »
Really cool build! Following along for sure. I have a 900F that I plan on giving a similar treatment, although on a bit more of a budget so will be using CBR wheels instead of spoked ones and a 919 RWU fork. Nice to see the Delkevic exhaust on an F build, I've been eyeing that same one and it looks good! I like the way you're going with the rear!

Ground clearance seems like it could be a problem? Have you done the rake/trail calculations? From what I understand one drawback of the GSXR front end is the small offset in those triples that could lead to really low trail numbers. I'm no suspension expert, but that's what I've been able to gather. You might be able to kill two birds with one stone and get custom triples from Cognito that are raised/winged (to gain some ground clearance) and with something like a 45mm offset?

Btw, what is the total length of those forks?

Good luck with the build!

Offline cb250nproject

  • Posts: 190
  • If you can make it better do so
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #22 on: Jun 15, 2017, 02:26:35 »
Hey Lights out

GSXR forks are 720mm with 17" rim the originals are 780mm with 19" rims, when I was looking into it i noted that CM offer a triple converion stem and bearing set, it ended up being a lot cheaper to turn one up on the lathe and grab the required bearings from a bearing shop. because CM offered the conversion stem i assumed (making an ASS out of U and Me) that it was all good and didnt check (rookie error).

I do intend to put a steering dampner on after a friend from MCR came unstuck on his tricked out cb 750. Im actullay only really concerned with the clearance or lack thereof :/ the Delvic pipes look sick but Im worried on a sweeping right hand corner it will be ground away. If worse comes to worse Dad just purchased a mill so maybe try to turn up an new triple if required

At the moment im trying to prepare the mould for the tail section I'm nearly happy with the shape I'll lay mesh over the mould before I pour the resin hopefully give it some more strength

see how we go, unfortunately my breaks nearly over :/ so the build will go on hold for 6 weeks booo

first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline LightsOut

  • Posts: 36
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #23 on: Jun 15, 2017, 05:33:59 »
The CBR900RR forks I'll be using are 732mm and I'll be using a 17" CBR/VFR front wheel (the Fireblade had a 16" but that's way too small). My 900F had the 18" front, but I assume frame geometry wasn't changed when they went to 18" from earlier years 19" so that probably wont't help me, I'll be in just 12mm better situation than you  ;D
With the CBR forks the original stem can be used, since Honda has been kind enough to use identical stems for a long time - so no conversion stem/lathe work or special bearings needed. Doesn't help the height or offset issue though :)

Darren Beggs (who built these beasts) uses winged top triples to regain some ground clearance when using shorter forks. Here are some pics of what they look like.

Looking forward to progress on the seat/tail. Where will you be putting the battery? Will a small one fit under the hump?

Offline cb250nproject

  • Posts: 190
  • If you can make it better do so
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #24 on: Jun 15, 2017, 07:11:27 »
Really cool build! Following along for sure. I have a 900F that I plan on giving a similar treatment, although on a bit more of a budget so will be using CBR wheels instead of spoked ones and a 919 RWU fork. Nice to see the Delkevic exhaust on an F build, I've been eyeing that same one and it looks good! I like the way you're going with the rear!

Ground clearance seems like it could be a problem? Have you done the rake/trail calculations? From what I understand one drawback of the GSXR front end is the small offset in those triples that could lead to really low trail numbers. I'm no suspension expert, but that's what I've been able to gather. You might be able to kill two birds with one stone and get custom triples from Cognito that are raised/winged (to gain some ground clearance) and with something like a 45mm offset?

Btw, what is the total length of those forks?

Good luck with the build!

The forks are about 720mm long with 17" rim as opposed to the original 780mm with a 19" rim  that was on it.

I'm not too sure of how the numbers work out, we fabricated a new triple stem and pressed it into the original GSXR triple, cognito moto also offer a replacement triple stem also but it was a lot cheaper to turn it up on the lathe ourselves.

I'll have to see what she rides like definitely need a steering dampener after talking to a mate from MCR who came off his cb750 from tank slapping, although his was a monster bored out and Dyno tuned.

If worse comes to worse Dad just got a mill
Which I reckon he is dying to use, will definitely be fabricating the rear set brackets with that.

Managed to snap up a few more goodies on line

So now Frankenhonda II will have some lungs

Today I've been trying to mould the seat pan up ready to

Those are some trick beasts.

I think once I put the fibreglass on the tail section and get that sorted I will make up a seat pan also. I was unable to put the resin and glass on because I had nothing to use as a release agent...poorly prepared.

There's some kick ass small batteries but I'm unsure which ones are best.

Just got some of these too but I don't think they will arrive before I leave.

You'll have to show us some shots of your build


Sent from my iPhone using DO THE TON
first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline cb250nproject

  • Posts: 190
  • If you can make it better do so
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #25 on: Jun 15, 2017, 22:33:27 »
Today I fibreglassed the tail section.

First I made a mould basically I used some foam for the tail section and cardboard for the seat pan


Then i taped the lot up so it wouldn't stick and also the tape give a much smoother finish than my bread knife made cuts.


I then put mesh over my mould to give the fibreglass a little more rigidity, but unfortunately I did not put wax on the tape as a releasing agent. So after getting it all nice and tied into place I removed it,waxed it up,then reinstalling the mesh


Then I cut out my sheets of fibreglass I used two different kinds one that is a cloth and the other a fibreglass matting. I think the matting is stronger but the cloth gives a nicer finish

Then I used a plastic sheet to cover the rest of the bike

Then lay the resin on and fibreglass

Now to wait for it to dry



Sent from my iPhone using DO THE TON
first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline LightsOut

  • Posts: 36
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #26 on: Jun 16, 2017, 05:00:58 »
Damn, those CRs are sexy! Fibreglass work looks good, giving me lots of good ideas here :)

I will start a thread once my build is properly underway. At the moment I'm planning and gathering parts... and (slowly) working on a GS550 build.

Offline cb250nproject

  • Posts: 190
  • If you can make it better do so
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #27 on: Jun 16, 2017, 05:48:00 »
We'll progress was slow and I'm all out of filler



I think I have the shape right tomorrow I'll go and get more filler and some more sand paper





Let's see how many runs I can get on the board tomorrow


Sent from my iPhone using DO THE TON
first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline cb250nproject

  • Posts: 190
  • If you can make it better do so
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #28 on: Jun 17, 2017, 06:39:15 »
Ok so I cut it out and she's a little rough (glass half full optimism)

She still needs a lot of work and I need to get a contour gauge to help me get the shaping spot on
hopefully this tool allows me to get the clean finish I want as paint only highlights your imperfections.



You can see where I cut too much off on the front left near the tank I'm not happy with that line and need to fix it up



So that's where I'm at it's a long way from where I want to be but hopefully I can make it work


Sent from my iPhone using DO THE TON
first cafe build was an incomplete learning experience, more of a test run for the real thing FRANKENHONDA II

Offline brad black

  • Posts: 138
Re: FRANKENHONDA II the 1982 DOHC CB 750F2 Build
« Reply #29 on: Jun 17, 2017, 10:12:10 »
I agree the disc does look odd, would it be cheaper to get it drilled? or just buy a brand new disc?

Also im trying to work out exactly what model of cb 750 had the 6 stud bolt pattern for mounting that disc, the other ones I had were all a 5 stud bolt pattern, that was off the original wheel that came off. dont want to oreder the wrong one.. again

Given how little the rear brake does i dont think I will go to the trouble of putting a nissin caliper on, I have ordered a kit and was going to strip down and refurbish the original caliper. I think the brake upgrade that came with the GSXR fork conversion will still make it like night and day.. thats wat I'm hoping anyway

you could ask max at planet discs.