Topic: 1972 CB500 "An Inherited Basket Case"

[SOHC4 Cafe Racer Fan]

Nice. Looks like there's a nice option for all those who were hoping Anders would develop a 550 unit.

[GV1390]

I want the curb weight of this bike to be at or below 375lbs (the weight of my Ninja), which is a net 50lb loss from stock.

With this data I feel pretty confident in being able to setup a series of road tests to quantitatively analyze and optimize carb tuning at the cost of ~3 one hour dyno sessions in my area. Plus I can use the same setup for my BMW 2002 build in the future.

Getting the weight down under 375lbs is achievable at ease, in my opinion at least.

More details on the BMW 2002 please......I've been looking for one of these for a while now, they are fantastic machines.

Work looks stellar, I am looking forward to seeing updates on this!

[calj737]

Getting the weight down under 375lbs is achievable at ease, in my opinion at least.

I'd be curious how you think that is easily achieved? Most the weight is in the motor, then the steering. Thats pretty fixed weight along with the tires, rims and spoke.

Personally, I'll be extremely happy if I can shed 40# form stock on my son's 500 build. and thats with an entire new alloy subframe, swing arm, and composite body work.

[GV1390]

Getting the weight down under 375lbs is achievable at ease, in my opinion at least.

I'd be curious how you think that is easily achieved? Most the weight is in the motor, then the steering. Thats pretty fixed weight along with the tires, rims and spoke.

Personally, I'll be extremely happy if I can shed 40# form stock on my son's 500 build. and thats with an entire new alloy subframe, swing arm, and composite body work.

He is running Excels like on my bike with the overall same motor weight and mine is lighter than said amount....I figured, in the direction this is headed, it should be easily achieved.

[bwaller]

Just catching up fantino, very cool. It's amazing what is "out there" & available, never knew about that E kit, good sleuthing! The bike I built for Deb is 395lbs, twenty less would be easy with a custom frame! Short of that lighter wheels, glass fibre tank, lightweight alt are all good steps.

I'm "long of tooth" enough to remember Cal Rayborn racing the XRTT. It's nearly the only HD that ever got my heart going!

As a guy that has a bike with limited lock to lock steering, I can tell you it's a nuisance, and would especially be for a street bike. Giving up a few degrees isn't hard to live with though. Moving the tank back too far looks unfinished so could you narrow the tank some in the front? I'm not a huge fan of that option either, but whatever it takes to make this work.

Good luck, I'll keep an eye out.

[slikwilli420]

Easily achieved? That might be a stretch. When you start getting rid of conveniences you may get closer. Going to kick only and ditching charging system components will help, but those are really track bike mods, and probably not relevant for the street. I am shooting for 390 on my race 750, which is about 130lbs of weight lost.

[GV1390]

Easily achieved? That might be a stretch. When you start getting rid of conveniences you may get closer. Going to kick only and ditching charging system components will help, but those are really track bike mods, and probably not relevant for the street. I am shooting for 390 on my race 750, which is about 130lbs of weight lost.

I suppose you are right. While I did ditch my electric start, I do however still have additional parts that weigh a bunch. My headlight/bracket are substantially heavy along with various other steel brackets.

[fantino]

More details on the BMW 2002 please......I've been looking for one of these for a while now, they are fantastic machines.

They're awesome! Getting harder to come by in decent shape for a reasonable amount of money these days, sadly.



It's a 72' roundie. I've had it for about 3 years, but haven't done much with it aside from replacing every wear component in the suspension and brake systems plus a few upgrades (IE sways, bilsteins, springs). Picked it up for a very good price (less than $2k), running, driving, straight and rust free with a 7/10 interior.

It's an automatic which is unfortunate, but that does actually facilitate a 5-speed swap with greater ease, as the trans tunnel is larger.

Eventual plan is to repaint, reupholster with recaros, LSD swap, convert to EFI and boost it. It's a much longer term project for me, one I'll probably break up into stages over a few years (once the bike is finished).

Work looks stellar, I am looking forward to seeing updates on this!

Thanks!

Just catching up fantino, very cool. It's amazing what is "out there" & available, never knew about that E kit, good sleuthing! The bike I built for Deb is 395lbs, twenty less would be easy with a custom frame! Short of that lighter wheels, glass fibre tank, lightweight alt are all good steps.

I'm "long of tooth" enough to remember Cal Rayborn racing the XRTT. It's nearly the only HD that ever got my heart going!

As a guy that has a bike with limited lock to lock steering, I can tell you it's a nuisance, and would especially be for a street bike. Giving up a few degrees isn't hard to live with though. Moving the tank back too far looks unfinished so could you narrow the tank some in the front? I'm not a huge fan of that option either, but whatever it takes to make this work.

Good luck, I'll keep an eye out.

Yeah, I'm surprised how little info about the Electrex kits there is, couldn't find a single post or review about an SOHCer running one, but the folks at Electrex were very helpful and responsive so I figured I'd take the risk. Looks like they use the same couple of parts for every race alternator kit they sell and make adapter plates to order.

Part of the challenge with this tank design is the XR frame is a very different shape and has a much flatter top. The tank can sit further back without revealing a big section of the frame. I've tried a few iterations and divots in addition to 5° less lock to lock is making the most sense. The divots look fine blended into the body work and the front section of the tank is pretty well obscured by fairing anyways. I don't feel any need to strictly adhere to the XRTT body work, but I thought it was a good jumping point to try a different look on our bikes

Not sure a composite tank will save much weight, given the stock tank is fairly small and single wall and the new design adds a few gallons of volume, haha. If I can save enough between the seat and tank to make the fairing a zero net weight addition, I'll be happy.

[GV1390]

That's a deal indeed! I've been looking for the earlier "roundie" generation but boy, do they pull a premium! I've seen a few great examples of them but, I simply can't justify the coin they pull considering how awfully slow they are.

[b52bombardier1]

I have regretted it every day that I sold my square tail light 75 BMW 2002.  Really great car though I wish it had been three years older and a tii.

Rick


Sent from my SAMSUNG-SM-N900A using Tapatalk

[GV1390]

I have regretted it every day that I sold my square tail light 75 BMW 2002.  Really great car though I wish it had been three years older and a tii.

Rick


Sent from my SAMSUNG-SM-N900A using Tapatalk

There is a guy local to me who has a tii but he wants an enormous amount of cash especially considering it's not in the best of shape and sits outside.

[fantino]

Haven't updated for awhile, so I figured I'd make a progress report

I've been doing a lot of contract work in the evenings and weekends designing composite tooling for the 777X. Bit of a double edged sword as I have way more cash flow than ever before, but it also means I don't have any time to work on personal projects. Nonetheless, managed to take a few steps forward:

• Combustion chambers, exhaust ports, valve faces and exhaust valve radii have all been ceramic coated at SwainTech
• Head is once again in Mike Rieck's excellent hands to oversize the intake valve seats and make relief cuts for the new cam
• Mike also sent the cam and rockers off to MegaCycle for hardweld + grinding
• Dropped my cylinders off at a local shop to have them bored for the new pistons and decked flat
• Started making a mockup of my tank design for fitment check
• Picked up a set of CR26s. I've never seen a set of carbs so shiny on the inside.
  
  

A few extra details on the mockup. I fiddled around with moving the tank back a bit, removing some steering lock angle, removing a bit of material from the tank and I think I came to a nice compromise. Retains most of the original tank shape, only loses 5 degrees lock to lock and still covers the entire backbone while revealing a little more of the headstock than originally shown:



So with that, I sectioned up the tank and have started working on making a full scale skeleton model out of .100" thick chip-board. I figured this stuff would be easy enough to cut through with a knife (it's only cardboard), but after I dulled a pack of exacto blades and cramped my hand after two sections, I decided the job would be better suited to a scroll saw. Picked up a little portable Dremel saw on amazon.



I have about three sheets worth of parts to cutout, but hopefully I'll be able to find time to do it between paying work this weekend. I'll post another picture when I have a completed model.

I will take a similar approach to build the seat model, but it will have the outside surface greatly thickened so I can fit check the inside surface to the frame.

Once I've determined the design looks and fits correctly on the bike, I will design layup tooling and take a similar, but higher resolution approach to build the molds out of 1/4" slices of MDF, finished by hand.

[calj737]

Know anyone with a Waterjet cutter? If so, have them knock out the skeletal templates. Very accurate and wicked fast. You would even use thicker material (like the MDF) to create your forms.

[fantino]

I have lots of contacts with router tables and WJs, but none who would do it cheap or free >_< I don't mind going the slow road for now.

Clearly the solution is to build my own CNC setup but alas, I haven't a shop to put it in.

[fantino]

Built my quick tank mockup last weekend, it fit with sufficient clearance on the frame and everything lined up as expected, no big surprises. Unfortunately I left it up on a shelf and the cats knocked it off, tore up the front supports which were undersized to begin with, so it lost a big section off the front before I could take a decent picture. Oh well.



Anyways, now that fitment is confirmed, onto the real deal. I need to add a flange on the outside or an inset on the inside to the front opening so I have a mating surface for the two halves of the tank when I join them together.

I was originally planning on building the mold components directly out of wood, but decided this was actually less efficient and more costly than just building a plug and making  splash molds. I've ordered up a ton of birch plywood blanks and I'm going to build the plug in a similar fashion to the mock up: cross-sectional layers at 1/8" or 1/4" intervals depending on the fidelity needed, doweled and laminated together. I'll sand out the steps and use a profile gauge to check the symmetry of my work.

This will be a time consuming process, but is a good winter project and will give me something to focus on while all my engine parts are crossing the country

[calj737]

And the final skin material will be?

If your cats ever go missing, look under my truck tires  (joking, don't get riled up).

[fantino]

Haha, the cats are indoor. They would never survive in the outside world, zero street smarts.

Still working out the final laminate, but tentative:

6oz 3x3 twill carbon
8oz 8H harness satin carbon. 0°
2x 5oz 4H harness satin kevlar. 0°, 90°
8oz 8H harness satin carbon. 90°
6oz 3x3 twill carbon

Probably a bit overbuilt, but i would rather err on the side of too much. I'll test a section of the mold with the laminate first to make sure I'm happy with it.

Should result in a ~.070" thick laminate with good strength and toughness. I will keep kevlar 1/2" in from trim edges because it's a pain to trim. I may add foam core to thicken up areas where fittings will need potted in and around the fuel cap hole.

As mentioned before, I plan to use a Novolac phenolic based epoxy for the laminating resin. This is the same chemistry as the Caswell liner kit and has the best gas resistance for a room temp cure resin system.

I'm mainly including the twill weave for looks. I intend to paint the tank black, but will leave a stripe of visible carbon up the middle for a hopefully subtle effect.

[calj737]

Excited to see the result!

[SOHC4 Cafe Racer Fan]

Yeah, that's going to be one spiffy tank.  Looking forward to seeing it.

[RAFster122s]

That is a lot ($$) of carbon in the tank.  I am surprised you didn't build the mold out of basswood or other material but mdf is a good material to work with as well.  I guess I will have to watch and learn your approach...it is always fun learning from pros.  I enjoy (ed) slope gliders, RC, but, here in NE TN suitable tree free slopes are difficult to find.  Out west the slope soaring is much easier to find sites. Most of the slope soarers use solid plugs and basswood is very common for those.

Enjoying your thread.

[fantino]

I decided to switch to using birch plywood to build a plug to pull fiberglass splash molds. It's more labor than building a mold directly, but cheaper and easier to get the result I want. I find it difficult to modify surfaces that exist in 'negative space' and it would be 3x the material to build molds with flanges and sufficient bulk.

We have production molds machined from MDF blocks at my work when it's for a low volume parts (<5), it's significantly less expensive than tooling board or fiberglass, dead easy to machine/finish and holds up fine if finished correctly. Recently we've been moving more towards SLA printing low volume molds instead, it's worked out well for room temp cure parts. Unfortunately either of these options are out of the question since I'm not willing to invest a couple thousand in molds and I haven't an NC machine to do it myself.

Most carbon fabrics are down to ~$20-30/yd. I should get roughly two layers per yard for a full width roll, so shouldn't be more than $100 in fabric, resin and bagging materials to pull a part.

[fantino]

I am currently on the lookout for an 85-87 GSXR750 swingarm. Pretty hard to find slabside parts on eBay, however.

[fantino]

Minor Updates:

• Mike has been working his magic, my headwork and cams are nearly ready!
• Autosport here in Seattle is finished up boring and decking my cylinders for the new pistons

More updates on the tank:

I estimated the time I was going to spend building my pattern from plywood, and well... at my "contract" rate, let's just say it didn't pencil out. With how much extra work I'm doing in the evenings, it would probably take me a few months to finish too. Soooo, I ended up getting a PLA shell of my tank 3D printed from 3DHubs instead! Not super cheap (about half the cost of buying an airtech FG tank) but frees me up to make more progress and make more money at the same time.



Next steps are to fill the inside of the two halves with expanding urethane foam, join them together, coat the outside with an epoxy product meant for filling in the striations on 3D prints, and sand/polish to finish the plug. Then the actual mold building can begin.

I picked up a vented, locking flush mount gas cap for a Ninja 250 on eBay. Still need to work out how to integrate the seal and latch mechanism. I also need to pick up a Pingle valve and some mounting hardware.

I also ended up buying a DIY 3D printer of my own. It was on sale for $150 (!!!) and I've wanted to build one for a while. It's only 9"^3 and needs a few improvements to put out really good quality prints, but I love to tinker. I plan to use it to build my seat form, mock up custom brackets and parts, build forms for cast urethane\rubber parts, etc.

[SOHC4 Cafe Racer Fan]

Man the 3D rapid prototyping is awesome.

[RAFster122s]

Interesting approach on the tank.  Sounds like a lot of work, but you should have perfect symmetry between sides of the tank.

 Since you have a 3d model of it in cad couldn't you build a sliced model with stacked pieces cut out of basswood to form a blocky version of the plug you then take chisels, rasps, planes, and sandpaper to bring it down to template outlines on a gridwork you plot onto the form from the beginning and maintain as you carve it.  With laser levels these days it is very easy to redraw the lines with some setup. A tripod to hold the level can help simplify that task.
With your outside templates you can sneak up on the final form and get consistent synnetry between sides.