Topic: Pin2Hot's 73 CB750

[calj737]

Because you opted to braze the bungs from the outside, really important that you insure you have no leaks. Or, whip around quickly on the inside with brazing rod just to seal the bung up fully. As long as you tie in the toes, you're golden!

And for someone who struggled a month ago getting that to weld up, it looks awfully damn good! 

[Pin2Hot]

Thanks Cal!  I intend to go back in and zip up the bungs from the inside as well.

I've been working on the electrical system when I'm not able to get into the garage and am toying with the idea of making a printed circuit board to minimize the rats nest that's inevitable on the front of the bike.  The board would host the relays required for my turn signal / halo setup, diodes and resistors for the dashboard LEDs and really simplify the wiring.  To be honest, I'm more excited about the wiring of this bike than the oil tank. 

[Pin2Hot]

Got the oil/air separator in last night, the only things left are the main overflow vent and a little tube to raise the return line up a bit higher, then it's time to button this thing up:

[SOHC4 Cafe Racer Fan]

Once you have this down, you can produce them and compete with Benji!

His combo tanks have had some issues.

[Pin2Hot]

Once you have this down, you can produce them and compete with Benji!

His combo tanks have had some issues.

Well here's hoping nothing crazy happens with this one.  I literally have no idea what to expect.  Am I going to get oil rocketing out of one of the vents?  Will the heat cycling crack stuff?  Who knows, only one way to find out!  I won't be painting or really doing much body work to the tank until I've fired up the engine and tested everything so if problems creep up, I won't be losing too much work I hope.

[SOHC4 Cafe Racer Fan]

Well here's hoping nothing crazy happens with this one.  I literally have no idea what to expect.  Am I going to get oil rocketing out of one of the vents?  Will the heat cycling crack stuff?  Who knows, only one way to find out!  I won't be painting or really doing much body work to the tank until I've fired up the engine and tested everything so if problems creep up, I won't be losing too much work I hope.

Fingers crossed.

[calj737]

Well here's hoping nothing crazy happens with this one.  I literally have no idea what to expect.  Am I going to get oil rocketing out of one of the vents?  Will the heat cycling crack stuff?  Who knows, only one way to find out!

The benefit of brazing those seams is increased ductility which will help immensely in preventing them from cracking. As for heat cycling of the oil, it won't ever get hot enough to make an impact to it. Its good to be cautious, but have confidence in what you've done because you'll be fine with the technical aspects.

[JoeCooley]

Just finished reading through this thread from the start. Great work and progress! I can't wait to see it all finished. Keep up the great work! 😎🖒

[Pin2Hot]

Just finished reading through this thread from the start. Great work and progress! I can't wait to see it all finished. Keep up the great work! 😎🖒

Thanks dude!

[Pin2Hot]

Got a couple things done last night.  Welded in the return pipe to separate the return oil from the supply a bit more and added a little gusset just in case.  I really didn't want to use full inch tubing (it's actually the same material I'm using for the rear hoop) but it's what I had on hand and it worked.



I only have one item left to weld in before I can button up the tank and that's the main crankcase vent.  In the act of cutting out the old vent from the donor tank, my angle grinder bit me pretty good.  I was being a total effing idiot and holding the part in my hand while cutting it so I deserved it.  Glad it wasn't worse but it definitely makes typing annoying.



So after I wrapped up my finger and swore off power tools for the night, I went upstairs and started working on the printed circuit board.  Because I won't have a headlight housing to conceal all of my connections, I'm creating a circuit board with weatherproof automotive connectors that will all connect up front.  Here are a couple screenshots (literally - I was being lazy don't judge) of the design thus far.

Schematic:


Board Layout:


This is the main connector I'll be using along with 3 other 6-pin connectors.
http://www.mouser.com/ProductDetail/TE-Connectivity-DEUTSCH/DTMF15-48P/?qs=cgQJD%2FpJz0zXnIuYhtM7Kw%3D%3D

I'll work on this board over the weekend and hopefully submit it to the fab house, Osh Park, who I've used before.  It's pretty crazy what you can put on a board these days.

[Pin2Hot]

I spent a lot of time this weekend working on the frame and creating my rear hoop.  I wanted a rather complex shape on the back end of the bike and was having a lot of trouble finding anyone locally to help me bend it.  I found a neat little pie wedge calculator here and did the math on my design.  I came up with 11 wedge sections to form the shape I was after.

Design:


Wedges:


Tacked Up:


Some original frame tubing I'm trying to reuse but probably won't:


After some grinding and fitting, I ended up being just 1/8" off my desired width!  It's flat and symmetric, ready to have roots ground out and welded up.  The next decisions will be what angle will the seat be placed and how long will the seat be.  I know I want the seat to angle up a bit but nothing ridiculous and I also don't want to have my nuts smashed up against the tank.  So I'm playing around with the length here after putting the bike back together to get a more accurate picture.





Makin progress!

[Pin2Hot]

Hey Cal, how long did you have to wait for your motogpwerks pipe?  I've been on a "list" since December with no word on a delivery date.  I'm starting to consider other options.  I would really like to stick with the werks pipe but I'm not sure it's going to line up with my deadline.  Anyone else out there wait this long?

[calj737]

He builds them in batches. Worth the wait in my opinion.

[Pin2Hot]

Thanks, Cal.  It sucks because I can't mount my rear-sets until I know where the pipe is going to end up.  I definitely want to wait but time's running out.

Quick PCB update, I got a lot of the high power stuff routed but still have a little more to do.  I'm not entirely happy with how the cables will enter the PCB but I think it'll look pretty snazzy once it's finished.

[Pin2Hot]

I finished the board and sent it off to the fab shop.  OSH Park is the fab house I use and they make creating printed circuit boards an absolute breeze.  Design the board, submit the design and 12 days later, you get 3 purple boards.  It's $5 per square inch which isn't all that bad for how quickly you get your design and the quality is second to none.  They're also made here in the USA.  I put a little flare on the back of the board that I'm sure you'll enjoy.  Here's hoping it works!

Top


Bottom

[calj737]

It sucks because I can't mount my rear-sets until I know where the pipe is going to end up.  I definitely want to wait but time's running out.

Won't you be mounting them via a separate bracket to the frame? If so, then simply deal with the bracket design and final position after your pipe is on. You can decide where the bracket will attach now, and make and educated guess from other's installations and get very close. The thing you need to consider, is how to attach the tail pipe for support after it's installed. There's a bung welded onto the tail that you can thread a screw into, but a strap or spring from there to... somewhere has to be resolved.

You don't want to not support the tail. It puts too much pressure on the exhaust studs and the pipe will hang down and bounce without that support.

[Pin2Hot]

Yeah I'll be mounting the rearsets with a bracket and I'll definitely support the rear end of the exhaust.  The exhaust is really the last major unknown on this bike and I'd like to get it resolved sooner rather than later.  I'd just like to get an estimate on when it'll be done so I can know.  I'll be patient.

Some frame updates.  I guess this was a bit of a milestone in that I finally put something back ON the frame instead of chopping it off.  I got the rear hoop lined up and tacked into place which is a huge relief mentally.  It's nice finally seeing the shape of this bike come into view.

Tacked and centered using some string:


Line of the bike with bonus Ruckus in the background (also please ignore the non-secured gas cylinder):



The next step is to add some supports to the seat which will hopefully match the angle of the upward swoop of the hoop.


There are a bunch of neat tube notching calculators on the old intertoobs (I used this one) so I printed out a few patterns to match the angles and this week I'll start to cope the tubes to fit them up.



Overall progress:

[Pin2Hot]

I spent the weekend in Austin at MotoGP and the Revival Cycles Handbuilt Bike Show.  I saw some incredible bikes and some great racing.  There were surprisingly few SOHCs within the actual show which mostly featured custom Ducatis, Moto Guzzis and old Bimmers.  Here's a Honda that was featured on Return of the Cafe Racer a couple weeks ago:


Some other favorites:


Revival Rebuilt Confederate


Super sexy BMW salt racer custom:


And one of my favorite things to see at a bike show . . . what people rode TO the show:





Tons of great people and great bikes.

[Pin2Hot]

Getting back from Austin definitely fueled my desire to finish this bike sooner rather than later so I got busy immediately.

I coped the rear hoop supports which turns out is a very satisfying process.  Getting these to fit up was a bit of a challenge but mostly due to the wall thickness of the material I'm using.  A flap wheel on my grinder really made easy work of getting these to fit up nicely.  Plus, taking accurate measurements ahead of time surely doesn't hurt.

Tacked into place:




I have some adjusting to do as the rear hoop isn't entirely square but I'll adjust that this week and begin final welding. 

I also had a nice little gift waiting for me when I got home, CIRCUIT BOARDDDDDS:



All of my parts fit!


Here's an annotated version to make things a bit more clear:


One final shot:


The surface mount LEDs show up this week so I'll get busy soldering this together.  I may regret not using a socket for those relays but the datasheet says they're good for 100k cycles so I think I'll be alright. 

[calj737]

Jumpn' Jupiter! Going all out on this thing, Pin 

[Pin2Hot]

Got a few more things done.  All of my circuit board parts came in and got everything soldered in.  I realized I'd made a mistake on the board itself which sucks but luckily it was an easy fix.  When sending a board off to a manufacturer, it has to go through a lot of checks before they'll accept the files you submitted.  However, one thing they DON'T check for is if you've routed every single signal.  I had missed a super tiny 1mm trace to a surface mount LED that indicates if the board has power.  Luckily a big solder blob solved that issue.

Here's the board before I soldered in the large molded four plug connector (the missing trace is in the upper right, between the resistor and LED):


I also finally, finally got the cover tacked into place for the oil tank.  Holy hell was that a pain.  It's incredible how much the metal wants to move and deform.  I guess it shouldn't be that big of a surprise as that whole tank is under a lot of internal stresses and after cutting a giant hole in it, I can't be upset if it springs back to where it naturally wants to be.  The solution?  RATCHET STRAPS:




Back on the bike and showing off the new superbike bars:




I was going to use some clip-ons I had gotten off of an old CBR600RR.  After sitting on the bike and feeling out the riding position, I came to the sad conclusion: I'm too damn old for clip-ons.  These superbike bars aren't much better but my wrists are going to thank me.  Plus, they don't look too shabby either.

[Pin2Hot]

I can finally say that major oil tank fabrication is complete.  I welded in the filler cap and pressure tested the tank.  Had it not been for this frickin oil tank, I'd have finished this bike months ago.  BUT I'm very happy I went through this effort.  My welding skills have greatly improved and it's taught me a lot about how metal behaves.

A few more steps remain before I can declare it totally finished, though.  I have yet move the petcock, seal both tanks with Caswells and deal with the flash rush that has accumulated.  After all that will come body filler and final shaping.  I'm actually looking forward to that part as it'll be my first real attempt at body work.

I'm expecting my exhaust sometime in the next couple of weeks (I ended up going with a RippleRock Hindle SS setup w/ a Cone engineering slip-on).  That will allow me to get my rear-set mounts sorted.  I'm still struggling to find someone locally to bend the swingarm hoop for me which continues to push back the monoshock mounting.  There's still plenty to do in the meantime so I'll focus on the work in front of me.

Sealed and pressure tested tank:


Filler cap:


On the bike:

[RuckyOne]

wow.... great read and amazing work!! I can't wait to see more of it!

[AlabamaCB750]

I wish you lived next door to me! Super skills!

[Godffery]

I recommend using POR15 for the internal sealing. it is much easier to work with & I have had great results with it.
http://www.por15.com/Fuel-System-Restoration_c_17.html