Topic: 1972 CB500 "An Inherited Basket Case"

[Camrector]

No rotor was off. Maybe my digital home scale that I used was a little off too.
I wouldn't think that there would be a 3 to 3.5 lb difference in crank weight.
Mine was a 76 cb550 motor. Maybe they beefed up the cranks a little on 550s?

[fantino]

No rotor was off. Maybe my digital home scale that I used was a little off too.
I wouldn't think that there would be a 3 to 3.5 lb difference in crank weight.
Mine was a 76 cb550 motor. Maybe they beefed up the cranks a little on 550s?

Perhaps so. The rotor for my new charging system is a scant 225g, so my final crank assembly will be pretty trim

Updates since my last post:

• +1MM Intake Valves showed up
• Head is at SwainTech to have the chambers, exhaust ports, valve faces and exhaust valve radii coated with thermal barrier coating
• Electrex RPK-1550 alternator system on order. Significant weight reduction in the overall system, + improved output and balance
• Picked up a fluoroelastomer coating for my gas tank liner. This stuff is *the business*, but it don't come cheap.

Did some design work on the tank. Still needs some tweaking, but here's a little peek





My inspiration came from an unlikely (for me) source: Harley Davidson. I was acquainted with the XR750TT and fell in love! Such an awesome story and gorgeous bike. I've tweaked a few things here and there, plan on using a more flush mount filler cap and had to make the shape and lines work for the CB frame, but overall I'm pretty pleased with my interpretation. I will pick up the fairing from Airtech in the future.

[Edit] a picture of the XR750TT for reference:


Next steps for the tank (+seat) project are as follows:

• Slice up the model and make a cardboard skeleton to mock up on the bike, checking for clearances + fitment
• Design tooling off part surfaces. I do this for a living, so this shouldn't be too much of a challenge. I'm going to make the mold directly out of 1/4" cross-sectioned slices of MDF finished by hand and avoid making a master + splash mold
• Build a 1-2 layer FG test part
• Build final part
• Trim final part
• Coat tank halves
• Caulk + bond tank halves
• Paint
• Install hardware

That's it for now. Need to let the bike fund recover a little bit, then sending the cam + rockers off to be taken care of, along with the head, by Mike.

[fantino]

Ill be interested in your experience with the Electrex. I've had an eye on it for some time.

The only possible objection I see to that beautiful body work is the Lock-to-Lock distance. The tank has culverts, but not really sufficient voids for clip-ons under street riding conditions. Road race makes sweeping turns, not 90* bends. Might want to factor that in if you plant to plan any street use. (Just an observation)

Yeah, absolutely. I had the same thought in mind about the bar clearances, I made a few adjustments near the front to try and make some extra room, but the model is still very much "in work", I haven't finished up the tunnel clearances + mounting either. I'm going to start with a quick CAD mock up of the forks and bars to go along with the frame to test the clearances, tweak and scallop (if I must) and then a physical check with the cardboard prototype to make sure I won't be slapping my tank silly on the street.

[fantino]

Haha, that would an interesting challenge. But no, I'm sticking with my MGP 4-1. My inspiration from the XR doesn't extend much past the body work as I don't care to run a drum brake up front or switch to iron heads   

[SOHC4 Cafe Racer Fan]

Very nice rendering of the bodywork.  Looking forward to seeing it come together.

[fantino]

Just a quick update, I wanted to show off some fancy new piece of kit

The Electrex alternator kit came in today. it'll be awhile before I'm able to test the output, it will be interesting to see it's capacity compared to the original system. It is a permanent magnet based system, so it will generate power without a battery which is pretty awesome. You can see the new pieces next to the old. The kit also comes with an Electrex regulator/rectifier built specifically for their race alternator systems and a wiring harness with good quality connectors.



The original alternator system (including cover) weighed in at around 8.5lbs, 1200g/2.75lbs being the rotor attached to the crank.

The Electrex alternator weighs in at a total of 1.9lbs! The rotor is about 285g/.6lbs, which brings my entire rotating crank weight Just under 17lbs total. The rotor is also very small and nicely machined (it is an aluminum core with the crank taper fit into a steel shell), so what little weight it does add to the crank is very balanced and close to the center of rotation.

Cal, you were correct about the clearances from the forks, to maintain ~60* of motion lock to lock, I'll need to pocket a bit of material out of the front (I've already moved the tank as far back as it can go) -or- sacrifice some range of motion. I suspect I may do a bit of both, take 5* off the total range of motion and remove what needs to be removed to add enough clearance. I know some road going sport bikes have as little as 45* of rotation in the forks, but I'd rather not have to do a 100 point turn to get the bike in and out of the garage 

If I can get through all my (paid) work this week, I will try to finish up the last few details on the tank design so I can slice it up and make a mock-up hopefully this weekend.

[fantino]

That is the STK-1550 you are thinking of.

The STK is a complete CDI ignition system with an integrated (lower capacity) stator to run battery free, with the intention of dropping the entire stock alternator setup. The stator setup in that system doesn't have enough output to power other electrical systems on the bike, so it wouldn't work for me but would be amazing on a dedicated track bike. It also looks to be a pretty decent value considering it includes the stator setup + a full CDI ignition system and coils.

I picked up the RPK-1550 which is a bolt on replacement to replace the existing alternator setup with a (much) lighter, higher output, permanent magnet alternator. It was actually a bit more expensive than the STK kit, but will suit my needs better.

[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!

[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.

[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

[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.

[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.