Topic: Pin2Hot's 73 CB750

[Pin2Hot]

Thanks for the kind words, guys.  It's been a lot of fun.  There's a whole lot more comin.

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

I think this is THE eternal debate here on SOHC4: whether POR15 or Caswell is better.  I've had a lot of experience with two part epoxies which is why I'm comfortable using Caswell (plus, I already bought it).  One of these days someone needs to do a deep, scientific dive into which is better.  Sadly, I'm only going to perpetuate the argument here...

I messed around last night trying to sort out my rearset mounts.  I had a plan going in thinking I was just going to cut out some plate and weld up a simple mount on the back edge of the frame...well as always it's never that simple.

Since I won't be using the stock pegs, I should have enough room on the engine mount bolt to put a plate on either side of the frame to which I'll mount the rearsets.  I'm also not going to use the drum brake pivot tube and lever adjuster so those are getting hacked off.  I'll probably have to figure out / adjust the pivot point of my rear sets (from a 2000 929) so that the drum brake can still be actuated but, like most problems in life, it can be solved with bending.

Rearset location with crappy mounting plate "drawn" in:


Side note: as a kid, the cool boot guard on Honda sportbikes always stood out to me so now I'm putting them on MY bike.

[754]

 Keep in mind 77/78 f rear motor and Peg stud are longer. That would allow you to mount a 3/8 or so aluminum plate firmly to frame, the mount your stuff to that..
 May have to shorten the longer suds on one side.

[Pin2Hot]

Another sexy option is to abandon the rear drum and replace it with a rear disk. You can do that in 2 ways, the SuperSport models had stock disc, Or, CognitoMoto makes a disc adapter to fit your stock hub retaining your Cush drive. That gets you to a rear master cylinder, loses the pivot tube, and easy to adapt your more modern rear sets.

If I hadn't already powder coated the rims and re-laced the original hub I might consider it.  I'll go full disc brakes on the NEXT bike.  I didn't realize Cognito has so many conversion options.  Pretty slick selection.

[Pin2Hot]

You don't have to change rims. The spokes are the same. Unlacing yours to replace with his is pretty simple (if you opt to). And he can send it powder coated directly to you.

I'll save it for the next project, already too far down the rabbit hole on this one already.   

Not much work this week but started the process of making a bracket for the rearsets.

Cardstock template:


Cut out and mocking up mounting holes:


I'm going to the ole metal store this weekend to pick up some 3/16 steel as well as some aluminum sheet to start making the battery box.  I've got some neat plans for that one.

And this little guy showed up last night (the pipe, not Bob laying in the background):


That's the Cone Engineering Big Mouth 13 that'll mate up to my Hindle SS exhaust that should be showing up any day now.

[Pin2Hot]

First, please enjoy the wonderful sunset we witnessed in mid-MO/IL this wonderful Memorial Day weekend.  We spent all weekend (and the previous weekend) building that dock cover.  It was a LOT of work and my back and legs are killing me today but it was worth it:



Second, enjoy the beeeeeautiful stainless steel exhaust that arrived from our friends up North, Ripple Rock.  The copper collar things are only temporary as I got studs that were WAY too long. 


The mid-pipe is going to get modified to shorten it up and angle it up/out.  That'll let me attach a hanger point on the muffler to support the rear of the exhaust from the rearset mount.


I'm going to miss my deadline of getting this done in time to go to Tulsa, OK next weekend but work will continue.  I hate having to keep moving my deadline but that's the way it goes sometime.  I'll keep at it.

[greenjeans]

nice looking exhaust.  Really digging those Cone big mouths

[Pin2Hot]

nice looking exhaust.  Really digging those Cone big mouths

Thanks!  I'm super happy with the fit and can't believe how light it is.  I'll chop up the mid-pipe tonight and try to get a final fit-up this week.  I plan on using the right rearset mount as a support point for the muffler.  Once I get it angled the way I want it should work out pretty well.  This'll be my first attempt at welding stainless so I'm going to practice on the part I cut out and try to set up some kind of backing gas configuration so I don't sugar the inside of the weld.

[Pin2Hot]

Do you know whether its 304 or 321 stainless? And it would serve you well to run a purge while welding it back together.

Not entirely sure.  I reached out to Kemp to see what grade SS it is so we'll see.  Isn't there a catch-all filler material that can be used for 304/321?  Something like 308 or 309 filler rod?  I'm not sure I'll even need any filler material as the sections I'm cutting out of the mid-pipe should just butt up against one another so I can wash the joint closed.  Regarding purge, I'll have to get creative with that because I don't want to have to buy an additional regulator just for this one weld.

[Pin2Hot]

Cal, great advice.  I was able to cut the pipe down last night and get the exact fit-up and placement I was looking for.  I'll use those techniques to tack and weld it up when I get a chance later this week.  It was pretty scary cutting that tubing but I was able to get it nice and square.

Before:


After (with custom electrical tape weld):


New angle dangle:


And great position to support the rear end from the right rearset:


It didn't occur to me until I saw the profile of the bike that it reminded me of my old GSXR's pipe:


It's really taking shape, getting pretty pumped.  After I get the rearsets and exhaust hanger mounted, I'll begin to focus on the oil lines and carbs so that I can finally fire it up. 

[SOHC4 Cafe Racer Fan]

At least you have a few attachment points (looking at the rearset) for some exhaust support.

[Pin2Hot]

I've been on vacation for the past week and haven't done a single thing on the bike but I thought I'd share what I did on the tail end of my time off.  I spent it working on 75 foot metal sailboat in Tulsa OK.  It's called SV Seeker and Doug, the owner, has quite a following on YouTube.  Check him out here.  I emailed him in February asking him if I could be a part of his build crew and he accepted.

I've been working since Friday doing just one of the many tasks still remaining on this ship.  When it's done, it'll be transported via custom transport structures that Doug is making (think moving a house) and it'll be moved to the furthest inland port in the US: the Port of Catoosa.  From there, it's 18 locks and 1000 miles away from the Gulf.  It's going to be a research vessel chartered by universities or anyone with an adventure in mind.  Doug and his girlfriend Betsy are incredibly wonderful people and it's truly been a great time working down here.  I still have this evening and a bit of work tomorrow but thought I'd share just a few photos of what I've seen down here so far.

I've been welding in some nuts that will hold down equipment to the deck which I thought was super clever.  I'll get some pics of my work later, right now we're avoiding the mid day heat but we'll get back out there this evening and finish up.

SV Seeker:


My work.  The holes in the deck hide some large threaded nuts that will let equipment be attached to the deck for whatever may require it.


Doug overseeing the arrival of his new set of wheels for the transporter.


It's been fun.  He's always looking for more help so check out his website and sign up to be a part of this massive project.

[SOHC4 Cafe Racer Fan]

WOW!!!

[Pin2Hot]

I'm having major issues finding ANYone in my area to bend up a hoop for my monoshock swingarm.  Anyone out there willing to help me out or point me in the right direction?

The people I've asked usually answer in one or all of the following ways:
- job is too small / we're too busy
- bend radius is too tight / I don't have the proper die
- I don't want to be responsible if it fails

I really don't want to buy a tubing bender just to do this one job and it's the ONLY thing holding me up from finishing.  Let me know if there are any good ideas out there, thanks!

[SOHC4 Cafe Racer Fan]

I'm having major issues finding ANYone in my area to bend up a hoop for my monoshock swingarm.  Anyone out there willing to help me out or point me in the right direction?

The people I've asked usually answer in one or all of the following ways:
- job is too small / we're too busy
- bend radius is too tight / I don't have the proper die
- I don't want to be responsible if it fails

I really don't want to buy a tubing bender just to do this one job and it's the ONLY thing holding me up from finishing.  Let me know if there are any good ideas out there, thanks!

I am not surprised as to these responses.  You may want to simply give them specs for the tube and bend and waive any responsibility/warranty of fitness for particular purpose.  In other words, will you bend me a tube according to these specs and I will waive any claims as to its fitness for your purpose.  You will have no one to blame but you if it fails, but you might have a better chance getting your tube, especially from the person making the third type of response.

[Pin2Hot]

I have an "ideal" version in mind but the radius required for it is what's causing a lot of consternation with the guys I'm hitting up.  All dimensions shown are in centimeters.  Tubing diameter is 1".

Ideal hoop - center radius of ~9cm (~3.5")


Realistic hoop - center radius of 5"

[Pin2Hot]

1" chromoly, 0.095.

[Pin2Hot]

Picked up some 1" 0.065 DOM today along with some other stuff to make my rearset brackets.  I found a guy who's willing to at least look at the project next week so hopefully it works out.  Fingers crossed.

[Pin2Hot]

I'm meeting with a local guy who's willing to take a look at the rear hoop so let's keep our collective fingers crossed!  He seemed optimistic that the design I'm after is feasible which is an even bigger bonus.

In the meantime, I was able to solve a couple problems I was facing.  I got some DOHC swingarm spacers in to help position the rear wheel and line up the sprocket.  So far things appear to be working out quite well.  The new chain shows up in a few days so I'll be able to see if it truly lines up.  I ended up using the brake side spacer from the DOHC swingarm and the stock K3 drive side spacer (which is thinner than the DOHC drive side spacer) on the drive side.  That put everything nicely in line.  IMPORTANT NINJA EDIT, that did NOT put everything nicely in line.  I'm posting an update now with my issue and possible solutions.

IMAGE DELETED

I also got some xylene and wintergreen oil and mixed it up 70% / 30% (respectively) to soften up my carb boots.  Man it works like a charm.  I left them in the solution for about 8 hours and it softened up the connection points just enough for them to slip on the cylinders and the carbs.

Please ignore the dusty engine:


I also got the carbs all put back together although I'm missing one #120 jet and I'm going to replace the small machine screws that hold the slide stems in place.  It's possible, dare I say it, to fire the engine up soon.  When that happens, I assure you it will be recorded in video for allllllllllllllllll to seeeeeeeeee.

[Pin2Hot]

So things aren't lining up on the rear end as I'd hoped.  I'm remembering a certain calj737 say "hey, chopping that swingarm like that probably isn't the best approach".  Welllll turns out I think you're right.  I found this out as I was double checking my measurements for my monoshock hoop and realized just how offset things are.  I kept noticing that the monoshock wasn't pointing at the center of the tire...

Closer measurements of the wheel position in the swingarm show that the DOHC brake side spacer and the K3 sprocket side spacer don't actually put the wheel in the center.  It's close but not great.  BUT what's worse is that the entire wheel is not on the center line of the bike.  In fact, it's 3/8" off to the right.  Moving the wheel to the center line of the bike does two things:

1) offsets the wheel in the swingarm
2) moves the rear sprocket to the outside (further left) of the drive sprocket

Possible solutions:

1) Chop off 3/8" off the left side (sprocket side) of the swingarm pivot to re-center the swingarm to the centerline of the bike.  That then requires a 3/8" spacer on the right side of the pivot to keep things tight.  But this doesn't solve the sprocket problem.  I know there are 3/8" offset sprockets from both CognitoMoto and CycleX but I can't tell if it offsets it to the correct direction (I need it to offset further out).  Possibly a 77-78 sprocket carrier will fix the issue?

2) Get a new damn DOHC swingarm and start again and do it correctly.  Still doesn't solve the sprocket problem but maybe the offset sprocket or the later model carrier will fix it.

I'm gonna dig through the forums and see if anyone else has run into this before but damn this sucks.

[Pin2Hot]

I'll post some new photos tomorrow.  Here's what's keeping me up tonight though: how is my sprocket offset when I haven't changed anything related to it?  It's the same cush drive and rear sprocket with the same drive sprocket.  It should line up!  I've got to have something flipped around or something dumb.

[RAFster122s]

Did I miss something...you have a DOHC swingarm rather than the SOHC swingarm that is what is different and it changed your offset on the sprocket.

I'll post some new photos tomorrow.  Here's what's keeping me up tonight though: how is my sprocket offset when I haven't changed anything related to it?  It's the same cush drive and rear sprocket with the same drive sprocket.  It should line up!  I've got to have something flipped around or something dumb.

[Pin2Hot]

Did I miss something...you have a DOHC swingarm rather than the SOHC swingarm that is what is different and it changed your offset on the sprocket.

What was bugging me last night, and I probably wasn't clear, was that the rear sprocket wasn't lining up with the drive sprocket when the wheel was placed on the center line of the bike.  I expect there to be an offset within the swingarm but not in terms of chain drive and wheel center line.  Both items are stock and have not changed, i.e. the width of the sprocket/carrier hasn't changed.

BUT it turns out in my haste/anger/hot-ass-Missouri night, I wasn't measuring properly.  I checked this morning and it appears the sprockets ARE, in fact, lining up.

Sprockets lining up:


Offset within the swingarm:


Gap on the brake side:


Overall look of the rear-end with wheel on center line:



I still have a 3/8" offset within the swingarm itself which requires a solution.  I need the wheel to be in the dead center of the swingarm because the monoshock hoop will visually amplify any offset as it'll be very close to the tire itself.  I'm think I'm going to remove 3/8" from the left side of the arm pivot to bring it back in line.  I have another backup backup plan but I hope it doesn't come to that.  Stay tuned.  Thanks for everyone's insights.

[Cafemoto]

Awesome work so far!


Sent from my iPhone using Tapatalk

[Pin2Hot]

I've definitely been slowing things down a bit to ensure I get this right.  I got myself a nice little laser to make sure I know where my centerline is.  I measured it in a few different ways, putting the laser close, far away, etc and came up with a good mark on the swingarm for where the centerline SHOULD be.

Frickin lasers:


I then used a small airsoft BB to find the true center of the swingarm (I'll probably use a heavier ball bearing to double check this measurement):


Annnnnd finally, a new DOHC swingarm (on bottom) to modify once I get it right.  I know my current swingarm is pretty much useless at this point so I'm going to make my correction on that one, check fitment and then transfer the right measurements to the new swingarm.


One thing I've also learned from this huge fckup was that my rear hoop is also not in the center!  So that's gonna get corrected during this swingarm swap.  It's pretty amazing how satisfying and infuriating this process can be.  But I've definitely learned how to deal with my problems one at a time and focus on the problem in front of me. 

One side note (while thinking of problems I've encountered) can I just curse the tiny screws that hold the carb slider stems in place?  I purposefully got new M3 10mm screws to replace those because they cause such a problem and IN THE PROCESS OF CHANGING THEM, I ruined an entire slide by trying to remove a stuck screw.  I got a replacement and everything is great but come on!  /rant

[RAFster122s]

Need the micro blue wrench when working on the small stuff.
You are not familiar with the blue wrench?  It is your torch and its blue flame, in this case a small one to have a fine jet of flame for more precise application of heat.