Topic: CB750 F2 Cafe Build

[Evening Echo]

Well, now that the Black Bike is dearly departed it became time to push on with the cafe build. I have split this thread from the other to continue this build log that started about 18 months ago. To recap, I had made a fibreglass seat cowl, bought a few shiny bits, made/revised a triple clamp,  and was just starting to sort out rear braking and knee dents..... This is how she stood about two months ago, not much new ad happened. Hope you enjoy and don't be slow with the encouragement and advice (or is it group therapy!!)....

James

[Evening Echo]

I wasn't too mad about my knee dent efforts so I decided to get a bit more aggressive. Given that the tank was in such bad condition I reckoned that even if it had to be trashed, no great loss! As it goes, I spent a bit of time at them and in the end am very happy with the result, it seems to flow much better with the seat now. You can see the stacks below your knees which is quite cool.

Of course all that cutting and welding has given me an appetite for more....

[Evening Echo]

So with all that chopping and cutting, I decided to stick an oil tank in there.... This is tacked up and I haven;t gotten around to tig'ing the seams yet. Bungs are turned and ready to be installed also.

Now for the first request for some advice. As you can see, I have threaded and tapped some nice brass fittings to the original oil spigots. They are 8mm copper lines flow and return from the oil tank. I reckon there is enough spring in this layout for them not to crack (I HOPE). This Internal diameter is one  mm less than the original lines (measured where I cut off the original line from the original tank fitting (9mm ID). I reckon I will hold more oil in the tank and there will now be marginally more pressure due to the smaller lines; my gut tells me that this is not going to be a problem but I was wondering would more seasoned cb heads have another view on this.

Pictures....

[SOHC4 Cafe Racer Fan]

I see you repaired the dent on the rear spine of the tank and sealed up the fuel door.  I like the aggressive scalloped knee dents.  What type of filler cap are you going to use -- Monza?  Bummer that you had to sacrifice a 1/3 gal approx. of fuel on the rear side, but no big deal if you are not riding longer distances.

I'm not sure about the pressure dynamics of your smaller copper lines.  I bet some of the guys who have fabbed their own oil tanks can chime in.

[Davidov]

The body work is looking good. Glad to see another F2 being put on the road.

For your copper lines, are they hard lines all the way between the tank and engine? I would put a section of appropriate sized rubber hose at the point where they go vertical (like a joint). Maybe even at two points.

Think of an automotive exhaust system where it usually has a flexible section.

[Evening Echo]

Good point on using a section of rubber somewhere, it will decouple, and hopefully save the olive joints at the brass couplers over time. I'll look into doing it where it would be least visible, maybe behind the removable engine mount and right under the tank joints.

The Monza cap was my first idea, but I got a gift of an old lathe from a family friend a few months back and have been into making my own parts; I'm sure it will wear off.....I have turned a brass gas cap but it is looking too chunky. I'm going to do up another one and will post for comment in the next few days, then can make a bung to suit.

I have some brazing rods on their way to put the rear panel into the gas tank, haven't brazed anything before so there is a hell of a lot of learning going into this bike right now, keeping it interesting and different for me. I didn't do much fab work before, just restoration on my other bikes.

[Old Scrambler]

Agree with Davidov on using lengths of rubber oil line................and the copper will turn dark green and then black due to heat and oxidation. I did use copper on a 1925 Allis Chalmers 15-25...........started to turn dark after one year.

Nice seat and tank shape.............

[Evening Echo]

Hmm, maybe I should change to something stainless....thanks for the thoughts.

The gas cap that I had made, definitely too clunky for the look that I am want: you can also see the new starter button fitted into the stem cap.

[Davidov]

Why not stainless braided lines? I'm almost certain you could find the right size adapter for oil inlet and return lines-to-AN line fittings.

[Evening Echo]

My idea for the oil pipe work is to use some nicely mounted solid sections where visible. Maybe a good compromise is to use some short braided sections at the end joints connected to bent stainless tube.

Got through some of the tig welding on the oil tank tonight. I'm pretty happy considering it is the first time I've made any sort of tank or sheet work other than the knee cut outs! I'll get pics up tomorrow. My advice for anyone starting from scratch, have a really tight fit up before doing any welding. My filler bung hole (!) was too large and I was chasing the pool of weld all the way around. Butt ugly welding but will do as a first effort.

[Evening Echo]

Got the oil tank welded; still need to figure out how I'm going to mount it all. Thinking about making a frame in 2mm x 30mm strap that the seat will rest on (bend a piece of strap the full length and contour of the hump), then the tank can mount to this also and a clamp under the oil tank. Then I can use this frame to hold the battery and the minimal electrics that I will use. Once I get all that done I'll be on the road to assembling all the varying elements.

Also found a GL front end on the bay as I would like to get rid of the comstars. If anyone is looking to offload a rear hub assembly ready to take spokes and rims i would be interested. I will also need the front hub for the GL Forks. I just had the cb750 F2 front fork castings polished but I think the spokes are really what I want. I'll post a wanted ad.

[SOHC4 Cafe Racer Fan]

FYI - the GL hub is identical to the spoked CB750 hubs.

[Evening Echo]

I didnt realise that due to the dual disc setup.

I drilled my discs from the comstars; are they usable on the spoked hubs........need to do some more research! Can the calipers from the 750 be used again?   

[SOHC4 Cafe Racer Fan]

I didnt realise that due to the dual disc setup.

I drilled my discs from the comstars; are they usable on the spoked hubs........need to do some more research! Can the calipers from the 750 be used again?   

The offset for the discs is different on the GL from the F2. Also the calipers are different. The GLs have larger bore pistons and are better.