Topic: Pin2Hot's 73 CB750

[Pin2Hot]

Hey!  It's been a while but things are still moving along.  I've found a few issues with my oil system since starting the bike but they're all manageable.  The biggest concern was a leak at the supply fitting and main oil drain.  A rubber gasket solved the oil drain issue and I'm still working on a solution for the supply fitting but I don't think it'll be a long term concern.

I had 3 problems preventing me from actually riding this thing.  Rear hoop support, swingarm pivot bolt and rear wheel spacers.  I picked up a tubing roller from HF and it did the trick.  There's a lot of slop in the device but I wasn't expecting too much accuracy.  The tubing ends up getting a bit skewed as it rolls through the bender but it ended up working out to my advantage as I needed mirrored tubes to support the rear hoop:



I wanted to avoid the chain so I used two pieces of bent tubing to form the main hoop support:



Ended up working out quite well:



It looks great on the bike too:



However, now that I see how nice these curves look, I mayyyyyy end up swapping out the straight sub-frame supports for two new curved pieces. 

[Pin2Hot]

Big milestone this weekend.  I got the rear end pretty much finished.  I've got to fully weld out the rear monoshock support but otherwise it's done.  I was able to get three things done: ream out the swingarm pivot, make spacers for the rear wheel and finally get the swingarm bushing and bearings sorted out.  Everything lines up beautifully. 

Reaming out the pivot holes wasn't something I had planned to do but getting a shim made to fit the old 73 pivot bolt didn't seem like the best solution.  I got this tool from McMaster and spent a LOT of time slowly expanding it to get the fit I needed.  My arms are tired.



I ended up going with the offset rear sprocket from Cognito Moto because it put the wheel exactly in line with the center of the bike.  Of course, any stock spacer that came with either the 73 or 80 swingarm was now useless.  I ended up making a 6.5mm spacer on the brake side and an 11.2mm spacer on the sprocket side.  This put everything all nice and centered.  Of course, anyone else doing this swap will want to measure and cut your own spacers.

Brake side spacer:


Drive side spacer and chain w/offset sprocket:


Years ago when I replaced the chain on my V-Strom I got this DID chain tool.  It's certainly paid off by now, makes putting on and taking off links a breeze:


I'm hoping to ride it this week to see where any weaknesses may be and then it's time for everything to come a part for final welding and paint.

[markreimer]

Man this is looking really good!


Sent from my iPhone using Tapatalk

[Pin2Hot]

Happy new year everyone.  I've spent most of the time since my last post figuring out a few things.  First, tuning the bike with my integrated oil tank is straight up impossible.  Accessing the carbs is a royal pain so I picked up a spare oil tank off of eBay to help get things tuned without wanting to set the whole bike on fire.  Definitely a downside to the design BUT I think this is a manageable solution.

I was having some serious trouble getting the bike to idle properly or to come off of idle without dying.  The only way the bike would rev from idle at all was with the choke on.  This fouled the plugs pretty quickly:



After reading literally every carb thread here, I did what I should have done from the very beginning: listen to the Honda engineers.  For whatever reason, I had my 657A carb needles set at the middle notch AND was using a needle from a carb rebuild kit instead of the stock Keihin units.  Setting the needles to the 4th notch from the top, ensuring my float levels were at 26mm, confirming my idle jet was 40 (main jet is 120 for the open exhaust), I finally had success:



Granted, this is only from idling for about 10 minutes but it revs great off idle, sounds so much more smooth and doesn't smell like I spilled gasoline all over the place.  I set up my homemade manometer to make an attempt and balancing but it looks like I need a reducer to prevent the fluid from getting sucked into the engine. 



I may just wait to balance things once final assembly occurs.  The main exercise here was to get a good gut feeling that my engine is healthy and I can move on to fit and finish items before the tear down begins.  I still need to make the battery box and get my rear brake figured out.  Oh, and a seat too, I guess...  Anyway, here's another video of it running last night.  Don't mind the smoke at the end, SOMEONE forgot to put a gasket under the valve cover and oil sometimes leaks out onto the pipes.  Hey, at least there's oil at the top end!

[Rnobx67]

  Raally good job Seems you can go further

[Pin2Hot]

Making some progress.  Mostly I've been addressing some issues with my embedded oil tank.  The original location of the return line hose connection was making life extremely difficult in terms of assembly and usability.  My solution, I'm sure, will cause some heartburn with some people but I think it's a reasonable trade off.  The return hose beneath the tank was being squished between the frame support triangle thing which shifts the tank to one side.  I wanted to go through the triangle but the flexibility of the hoses and the ability to get the tank on the bike made that solution impossible.  SO, I chopped out a section and welded in a hoop.



Solution?


Reality:




Turns out, threading my new return line through the new frame support hoop AND actually seating the tank don't work.  I had to cut the hoop in half to make it all work.  This isn't ideal but I don't think the bike is going to bend in half as a result of it.

I learned a few lessons with those braided line hose fittings by over tightening one of them and snapping it off.  I don't believe I'm using the right fitting as they never seem to want to seat against the ferrule without exerting some extreme force on the fitting itself.  I'm gonna order some new ones and make a new line anyway so we'll see.

I also worked on the headlight a bit.  Kinda interesting to see how many custom bikes I've seen lately have been using wood as well.  I thought I was being unique when I first planned this a year ago but looks like it's catching on.  Still a bit of work to do on it such as cutting the dado to inlay the LED strips for the turn signals taht run around the perimeter of the plate but essentially this is what it'll look like when it's finished.  I'm pretty happy with it but don't really have any idea how it's going to be mounted to the front of the bike.  I'll cross that bridge when I get there.

[Pin2Hot]

I started working on getting the tank to look somewhat respectable this weekend by converting some rust and starting on the body filler.  I used Eastwood's Fast Etch to prepare the surface of the tank to make sure I had zero rust.  PS, definitely wear a respirator...

Soaking:


After:


ALL of the rust disappeared and I ended up with a uniform tank ready to apply filler.  I'm using a commercial brand body filler (Fastline - Fast Light) that a friend at a paint store set me up with.  Doesn't have much work time but I was able to fill the big dings and dents.  I've got a LOT of work still to do but it's nice doing the first real cosmetic work to the bike.



I also got busy working on the battery box which was one of the last big items to tackle.  I'm going to weld a mounting bracket to the frame and the battery box will bolt to it.  I went this route because in the event I need to use a different battery due to a Li-ION meltdown, I can build a new box and bolt it right up.



It'll weld the bracket to the frame above the chain, on the left side of the bike:

[Rnobx67]

I think you gonna be check those powerfull LED lights, some of them could be very hot ! need a big aluminum plate for heat dissipation. And sometimes also a fan, but maybe I'm wrong.

You are a perfect welder again otherwise

[Pin2Hot]

Thanks for the kind words. 

The lights I'm using have massive heat sinks on the backs of them.  You can them sticking out from the back.


The fins will be exposed to the air so hopefully I won't need a fan.  I'll definitely keep an eye on the temps as they're running though.

[Pin2Hot]

It's time to dismantle.  I got all the oil fittings sorted and routed so I no longer need the engine in the frame.  I'm to the point where I can take everything apart and get it ready for paint.

I cleaned the workbench up to make room for the engine and to give me some space to weld on the frame.  A lot of the sub frame is just tacked into place so now's the time to weld it all out.



Taking the engine out:


Everything disassembled:


I still had the center stand mounts to take care of:


I evened up the holes left by chopping down the frame, getting ready to weld those holes closed:


Holes closed up, will grind things down to make them pretty:


I ended up shoving my thumb into a portaband making those damn plugs so I'm typing with a big fat bandage on my thumb.  I deserved it though, wasn't being safe and it could have been a lot worse.  But now I can barely take a piss without my thumb throbbing.

Next steps: final welding on the frame, media blasting all parts that need it along with priming.  Then it's time to paint!  Hopefully things will start to look final soon enough.

[Pin2Hot]

Ok, remind me to never do pie cuts for a frame hoop . . . after 4 hours of tedious, out-of-position welding, the frame is welded out.  The quality ain't all that great but I spent a lot of time on the welds that matter most.  The patterns I made for the seat still fit which tells me it didn't move all that much during welding which is promising.



I welded on the battery box bracket and mounted the box itself.  On the box is the main starter solenoid (incorrectly mounted upside down in the photo).  It's a neat unit, got it from Revival Cycles and am using it because it works very well with the m-Unit.  It has the main fuse and spot for a spare integrated into the starter solenoid.  It also has a connector for supplying fused power to the m-unit itself as well as the aux power:



Lots of welds:


One of the big mental holds-ups I've had on this project was how to get the right satin finish I want on all of the aluminum throughout the bike.  Watching jafromobile's videos on YouTube have been super helpful in many areas but in aluminum prep specifically.  His whole series on porting / polishing heads (

pointed me to dremel buffing wheels.  I bought two of these from amazon: https://www.amazon.com/gp/product/B010NLHCOW and was able to get my rear wheel hub and brake carrier polished just the way I wanted.

This photo doesn't actually show the satin finish (derp) but shows that I finally got the rear wheel finished:


I realized while doing the rear wheel that I had messed up the spacers.  There's a collar that fits between the sprocket carrier and cush drive that I was using on the OUTside of the sprocket carrier instead of between the carrier and cush drive.  This changed the spacing and forced me to make a new spacer.  Fortunately I had the material laying around to do that but I'm pretty sure once it gets fully assembled, I'll be modifying them again to get my chain to line up perfectly again.

I've crossed another mental barrier having the frame welded out, it certainly feels much more finished.  When banging it around, the frame "rings" like it used to instead of buzzing like a bin of rusty parts.  I'll be working on the seat next so a bit of woodwork and upholstery is coming up.  Thanks for reading!

[DurangoCB]

Hey, chalk it up to lots and lots of welding practice. 

I recently bought a set of those Dremel abrasive polishing wheels and was disappointed by how quickly they disintegrate.  They do work well, though. 

[Pin2Hot]

Hey, chalk it up to lots and lots of welding practice. 

I recently bought a set of those Dremel abrasive polishing wheels and was disappointed by how quickly they disintegrate.  They do work well, though. 

Yeah they burn out pretty quickly especially if the surface is rough to begin with which I guess makes a lot of sense.  Getting 40 of them for $11 bucks from that amazon link makes it seems a bit easier to deal with their durability.  Sure as hell beats beating up your fingers trying to get into a tight spot with 120 grit paper.

[Pin2Hot]

And some 1” 0.063 with 1/16” er70...

Great stuff, Cal.  I'll try that next time.  And there WILL be a next time despite what my wife says.  Please don't tell her I said that... 

[Pin2Hot]

That's cool, I can use the fancy button on my torch to go full blast and wash it in.  I'll give it a whirl. 

[Shtonecb500]

I have the same kind of airbox for my 550, that one period correct, right?

Are you going to keep that airbox?

[Pin2Hot]

I have the same kind of airbox for my 550, that one period correct, right?

Are you going to keep that airbox?

Well, not sure yet really.  I think I'm gonna run with it and see how well it works.  I've heard people either love or hate these things.  I actually had to make it a bit skinnier to a work with the monoshock so not sure how much that's going to impact how well it runs.  Do you have any experience with them?

[Pin2Hot]

Guys.  A miracle occurred in the garage last night.  For the first time on this project, a solution to a big problem solved itself.  I've been struggling to find a solution to actuate the rear brake on this bike.  To make routing easier, I decided to use a rear brake cable conversion kit from Dime City Cycles (https://www.dimecitycycles.com/dcc-customs-rear-brake-cable-conversion-kit.html). 

The problem I faced was finding a suitable place to mount the front cable stay without welding on some ridiculous looking tab to the frame.  Then I saw it: the 2000 CB929 rearsets I'm using have a threaded hole on the back side of them for what I think was the rear brake cylinder mount.  All I had to do was drill a hole next to it for a small post on the cable stay that I think prevents it from rotating.  I just found it pretty crazy that a modified 73 frame, running a 1980 DOHC swingarm, 2000 929 rearsets and a custom cable bracket all magically worked out.

The front cable stay bracket attached to the back of the rearset:


Still a bit of work to do here such as shortening the arm used to keep the drum in place but the cable will be routed up and fixed to the swingarm itself:


Looking backwards.  The original rear brake shaft arm will be modified for this application.  I need to build out a linkage system on the brake pedal which I'll detail soon.

[DurangoCB]

It's nice when that happens!  Though I don't think all the credit goes to the rear sets nor to Luck... 9 out of 10 people wouldn't have the eyes to recognize that there was a solution to be had there. 

[Pin2Hot]

I've spent a lot of time lately figuring out the rear brake.  A lot of slicing and dicing has occurred to get me to this point, mostly by breathing new life into old unused parts from the tear down.  And like everything else on this bike, it's taken a LOT longer than I imagined just getting the damn rear brake working.  Although, I'm very happy with the function of it even though I still need to make the linkage to truly make it work.

If there are any cycling enthusiasts out there, I did a flop and chop on the rear brake pedal arm as well as the pedal itself to make the rearset linkage operate in the correct direction.  OEM parts ready to get hacked apart:


Lever arm shortened, rear pedal hacked up:


Drum brake arm chopped up to make it straight as opposed to off-set:


New brake arms all welded up:


New straight drum brake arm:


Brake linkage all lined up.  Notice my "oh-#$%*" spacer as I didn't shorten the arm enough, it ended up working out OK though.  Also, don't get used to that cable stay bracket...


Ok, so I'm embarrassed by this part.  Just know that it works and I'll make it prettier later.  What I thought was a gift from the fabrication gods ended up not working.  I had to modify that cable stay for a billion different reasons so this is the solution for now.


I still have yet to weld on the actual rear-set pedal arm and figure out the linkage but I think that's going to be somewhat straight forward.  Definitely a lot easier than this damn thing.../.,amsdsdfl;kasdjdf

[Pin2Hot]

I'm turnin right!

[DurangoCB]

Now that looks tidy!  Nice work.  Can you give links to those lights?  And did you fab the brackets or just pick them up online? 

Really looks nice. 

[Pin2Hot]

Thanks dude.  They're these cheap little things:

https://revivalcycles.com/collections/for-your-ride-bestsellers/products/led-light

Pretty sure it was this tab: https://www.aa-mfg.com/shock-tab-2295  Since these were for a larger tube diameter, I had to grind it a bit to make them fit a bit better. 

PS these lights a BRIIIIIIGHT.  That battery I was using was almost totally dead and they were blinding.  At least people will know I'm turning!

[Pin2Hot]

As is tradition in my garage, the previous month has been spent standing in silence, staring at the frame second guessing everything I've ever done to his project.  SO, in true form, hardly anything has been done.  I spent two weeks worrying about if things are truly square or how much did the welding draw the hoop to one side?  Is it noticeable?  Am I going insane?  I should just give up. 

I have not given up.  I started to work on the seat "pan".  I'm trying to lay out the supports for the pan which will also serve as the mounting points for the regulator/rectifier and mUnit.  The pan is two layers of this bendy plywood my brother had in his shop which will be laid between the frame rails and curved into place.  A few layers of walnut veneer will go on top/bottom.  There will probably be a single layer of e-glass fiber on the bottom to waterproof it.  On top, a skinny padded area will sit atop the pan made from 5/8" gel material, covered in suede with some fancy stitching. 

Here's the pan being fitted:


So that's the extend of the work.  In one month....  To help me get over my lack of progress, I took a functioning bike and made it non-functional.  Ya know, to knock something else down a peg or two.  Actually, I've been neglecting my poor little Ruckus for quite some time now and decided to give it a good makeover.  New cables, new jets, new drum brakes.  Basically all the consumables on the bike are being replaced.  And good thing too.  As I was pulling the carb off, the throttle cable broke on its own so I'm glad I did that now before I got stranded somewhere.

Two non-functional machines:


Ruckus carb:


Funny comparison: CB750 vs. Ruckus forks.


"Clean" Ruckus:


This week will be spent waiting for parts for Scoots so I can get it out of the garage.  After that, I'll weld in the seat pan supports and get the frame blasted and primed.  I'm hoping things accelerate after I get the seat figured out because that's truly the second to last big issue on the bike.  The final issue will be the headlight mounting.  Not looking forward to that one...

[DurangoCB]

I had a similar weekend- I could feel my project eddying out at the most dangerous point so I sacked up and starting knocking a few things out to get over the hump. 

That Ruckus has a 2-bolt bicycle stem.  LOL 

Keep at it amigo!