Topic: 1972 CB500 "An Inherited Basket Case"

[Camrector]

^ what we all should have done!

[fantino]

Or you could slide in a 674cc, ported and Megacycle cam'd CB650 engine!!  More torque and hp and it bolts right in!

^ what we all should have done!

True - or - if we really wanted to be far more logical, we all should have just bought a better handling, higher power, cheaper, more reliable middle-weight from a later era :-p

I'm far too attached to the bike as a package to ever go to that level of frankenbike. There's a certain level of non-originality I can roll with (this goes up dramatically crossing over from mechanical to electrical), but all in all, I want to stick with the base platform and see how far I can take it.

I'm liking it! Twinsies! I believe from what the general consensus is here is that what webcam advertises and what is actual are two different numbers. Member bambuhiphop provided an excellent chart showing Megacycle numbers compared to Webcam numbers here. http://forums.sohc4.net/index.php?topic=124348.0
You did mention that you had rebuilt stock carbs and we're going to explore cr26s.
Cr26s I feel is what you would want from what you are describing above.
With the piston choice of the 61r 592cc, I think you would want the 126-20 as well.
Again those Pistons require no valve relief milling with the 126-20. Plus the extra compression and head work would benefit from that cam.
Larger intakes +1.
Larger exhaust is not needed.
That's the Full Monty recipe.

Another great recipe is what cal speaks of. But with that one you could just use the 61s 592cc Pistons ,126-00, stock carbs, stock intakes.
I'll be doing this on my "sleeper" build.

I saw that thread, but I don't have enough know how to really understand the differences in duration and lift and how they shape the powerband for these particular bikes. I'm mostly going off word of mouth at this point.

Sorry to style bite But I think you're correct, it seems to be the winning combination to get the best out of this motor. Obviously the carbs are a bit of an investment, but one I was already prepared to make, so I don't otherwise see a huge difference in bumping up to the 126-20 + 592R combo over the 126-00 + 592S.

I can do the head + rocker modification for cam clearance at work, so the only other pieces I will need to send out are for the +1 intake valve mods and having the rocker + cam hard welded.

Luckily I have a windfall of extra contract work coming up in October that will help offset the additional project costs

[fantino]

Mike is the man! I was really happy with the work he did when I had my stg3 port work done back in 2010. Care and detail of a master craftsman

He actually has my rods right now for polishing and balancing, though there was a minor snag in that one rod appears to not be from the same set! Not sure what's up with that, but the pedigree of this bike is largely a mystery.

[fantino]

Now, what about an exhaust system to get the air out? 

I like the MotoGP exhaust the best, but they seem a little tough to get a hold of? I haven't had any luck so far. The Lossa pipe appears to be very similar, but I haven't seen much buzz about folks running that pipe.

Honestly, I wish there was a good, light(ish) weight performance 4 into 4 for these bikes. I love the look and I love the sound, and there's something about the tunability of 4 carbs and 4 pipes that I find really appealing.

[Camrector]

Check out the Hindle 4-2-1 at ripplerockracers. I have the motogp pipe on my ladies bike, awesome but loud. The Hindle sounds great and the quality is superb.

[Camrector]

Btw are you planning an oil cooler? I'm on the fence.

[fantino]

Check out the Hindle 4-2-1 at ripplerockracers. I have the motogp pipe on my ladies bike, awesome but loud. The Hindle sounds great and the quality is superb.

Thanks for sharing! That's definitely something to think about. It looks well built and the exchange rate is definitely in my favor. I appreciate that it's something different and - though I'm always skeptical - appears to have some solid numbers behind it. The Yosh style pipes, while awesome (and as you say, loud) feel like they have become the de facto pipe for the majority of builds.

It looks like BCR has built some nice looking 4-4 systems for 550s in the past, but I can't justify $1200+ for an exhaust system, especially one that in reality weighs more and likely doesn't offer much difference from a performance perspective.

Btw are you planning an oil cooler? I'm on the fence.

I've considered it, but I haven't seen much evidence so far to suggest it will really be necessary outside of a race track or Arizona. If in practice I see evidence to the contrary, I'll go back down that road again. It's a pretty easy bolt on at the end of the day.

[fantino]

^excellent advice and reminds me I should check the clearances on the pump rotor to see how it's held up over the years.

I'm on vacation in Montreal right now, so I have no idea why I'm posting right now, haha.

I don't wish to get too ahead of myself, trying to keep my focus on the engine for now, however, weight has been on my mind. 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. I've added a little extra weight with external hoses and dual disc brakes, but the overall trend is going down:

-Center stand delete (~10-15lbs?)
-crank lightening (3-5lbs)
-Alu rims (3-5lbs)
-Ii-ion battery (5lbs)
-exhaust (no idea what stock weight is, I imagine 5-10lbs potential here)
-phenolic brake pistons (.25 lb)
-cross drilled rotors (.5lb)
-Alu clip-ons, shaved top tree (1lb)

That only brings me, at best, half of my goal ignoring the likely 10+ lbs of additional weight I'm likely to add. Other areas I have ideas on removing weight:

-Fenders: stockers are pretty heavy, but I don't want to run without. I may make splash molds and pull some bagged carbon Fenders. Same deal with side and whatever I do for an electronics tray. If I have a true area of expertise, composites is definitely it. I still dream of making my own tank, but it's a pretty big endeavor. Maybe 5lbs to save here.

-Seat: Stock is really heavy. A stiff carbon base wrapped up in a nice slim leather cushion with some higher density foam (I do a little leather upholstery work on occasion) will save a pound or two, but probably won't do much for comfort

-Frame: if anything, the frame and forks could use extra weight in gussets and bracing. Other than the passenger peg brackets, ignition switch bracket and rear seat rails, I don't see much to lose.

-Starter: I could delete the starter, but I don't really want to. Cost to benefit ratio isn't there for me, especially not until the bike is running well.

-Lighting: slimmer LED lighting all around will probably shave a couple pounds off

-Switches and other electrical: the m-unit, single mg gauge and momentary switches will probably shave a couple pounds off the stock electrical system. Need to find a different horn too, the stocker is ludicrously heavy for what it is.

I'm not sure I'm looking likely to hit my target so far, so any ideas are welcome, keeping in mind I'm not amenable to turning my covers into swiss cheese. Not into the look. The higher up the weight savings, the better.

I've also been thinking about how to plan for tuning the bike. Dyno days don't come cheap or easy and seat of the pants is waaaaaay too subjective and unreliable for my engineer brain.

I'm thinking of investing a little coin in Innovate Motorsports data acquisition and logging units. Primarily I would like to log a wideband, RPM, MAP and a TPS, like a simple EFI setup uses. Manifold pressure is a little tricky if I end up running v-stacks instead of a stock style manifold (EDIT: nvm, just remembered a pressure sensor before a TB/carb is a BPS, not a MAP. Either have to run 4 pressure sensors or run 1 and make the assumption the other 3 are balanced :-/). It would be nice to monitor oil temp, exhaust temp and ambient temp as well.

http://www.innovatemotorsports.com/products.php

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.

[fantino]

Yeah, you're probably right on optimistic numbers. I went back and checked some of the numbers I had in my head from past builds and I think 385 dry is about as light as I've seen reported on anything that wasn't a radically lightened track bike (supposedly TG and Howell had their builds below 320 dry). Add 30 for gas and oil and 375 wet is a long ways away. Still, I would like to shed weight where I can. Primarily for handling, not P/W. Taking weight off the wheels would probably be the best route in that regard, but I'm not super keen on switching out the hubs or going to a floating rotor setup for the time being.

As for the center stand, I've never had one with this bike, so I was just making a guess

Regarding the Motogadget gauge and sensor capability - there appears to be no provision for logging or outputting the data, so it unfortunately wouldn't help much. I'm not comfortable trying to keep my eye on gauge numbers or operating a menu while in motion. Or trying to remember and correlate any of that information.

I definitely agree that hitting up folks with similar setups for a base tune is the way to go starting out. I'll have to get in touch with Funjimmy, looks like we actually live in the same corner of the world, albeit separated by a pesky border.

The big appeal of data-logging capability for me is being able to collect the response of real world load conditions and to track my riding style. Since carbs require so much more compromise in regards to tuning for max power vs tuning for best driveability compared to say - developing a fuel map for an EFI setup, this sort of data seems invaluable to really dialing the carb in. I can't imagine being setup to collect more data during dyno runs would hurt much either

~$500 for this capability actually seems like a pretty decent value, especially spread over a couple different projects and given that I can recover much of it if I decide to sell the setup later on.

[SOHC4 Cafe Racer Fan]

Personally, I would swap out the stock battery for a AGM battery.  Unless you have tight space constraints or plan to race, Lithium batteries can be finicky.  They have tuns of cranking power, but if they dip below a prescribed voltage, they do not come back.  They seem to be all good until they go in one fell swoop.  I've had three of them work like wonders and then take a crap on me the morning of a planned long ride. 

Shorai has a charger that has a trickle mode like a Battery Tender, so if you are going to buy one, I'd recommend theirs.  It's the one branded lithium that I've had not issues with.

[Camrector]

Never had a problem with Shorais either.
Also
https://www.ebay.com/itm/122128832311
Looks like they are back.

[fantino]

I was aware Li-Ion in general have pretty flat discharge curves, so it's harder to monitor a weak battery as it doesn't give much sign of giving out until it's out of charge. When you say "they don't come back" do you mean the battery permanently will no longer hold a charge?

Random thought... Even if these bikes were running on a permanent magnet alternator, if they were setup with an M-unit and keyless ignition and the battery went kaput, the bike would still be disabled without energy to power the computer. I wonder how tolerant the M-unit is to low voltage and fast power cycles? Does it take a moment to initialize or can it instantly power the ignition system?

https://www.ebay.com/itm/122128832311
Looks like they are back.

I'm about to get some more fun stuff on order as well.

[fantino]

Okay, cool! Thanks for the extra info.

Granted a key is still needed for the steering and seat lock and I see it as more of a convenience rather than security feature anyways, but does it not somewhat defeat the point of having a keyless ignition system if it can be easily bypassed? ^_^

[fantino]

Haha, true. I guess without an immobilizer type ignition system that requires an RFID handshake these bikes are inherently pretty easy to steal. But that  would require the ignition system and key system to share the same computer and it's not as if those systems are terribly secure these days either, even less so on something that two or three guys can lift into a truck ~_~

[SOHC4 Cafe Racer Fan]

Yes, once a lithium battery discharges to a certain threshold voltage it will not recover.

[fantino]

According to Google Translate, the Japanese means "Horsepower". Nice touch. No regrets picking this up, it's really beautifully made. I didn't realize the baffle end cap was a machined piece with all those reliefs, looks pretty trick.

I also placed a big order with Dynoman, in addition to picking up a set of 550 jugs to overbore. Save for the cams and internal coatings, I should have just about everything I need for the motor at this point, save for a few odds and ends.

My pockets are feeling pretty light at the moment 

[Camrector]

Nice. I haven't seen one with that end cap. Looks sick.

[fantino]

Still just making little bits of incremental progress here and there. I have two broken down 15 year old BMWs that need my time and money at the moment   

Pistons, MLS headgasket and viton base gasket showed up from Dynoman. They're so pretty:



These will eventually get sent out for coating, but I will wait for dry fit with the cam as Cal advised. The 126-20 *shouldn't* interfere, but I'd rather be safe than sorry.

550 jugs showed up this week, I'll clean them up a bit this week and hopefully get them off to be flattened and bored for the new pistons. I work next to a big diesel marine shop that does good work. Apparently they can work on cranks up to 10' in length :O

Speaking of cranks, lightened crank is on it's way back from APE right now.

I finally finished repairing a past blunder with the oil line conversion on the head. New inserts are installed in both sides, flattened, fins clearanced and ready for an M10 banjo fitting. I'm going to send the head out to have the combustion chambers and exhaust ports coated with TBC at Swaintech this week. Once those come back, the next step is to get them to Mike to have the intake valves oversized and valve seats recut.

I picked up some fittings for the clutch conversion. Was originally going to run a hard line through the hole in the cover next to the clutch mechanism and up through the original clutch cable hole with a fitting to connect to a soft-line. I bent up a few iterations, but nothing has really looked quite right. The offsets are too close to make a single bend and a big sweep of hard line on the outside of the clutch cover doesn't look any tidier than just running a flexible line over the clutch cover, so i will probably just go with a single flexible line.

Double checked my calcs on the clutch conversion, I should be able to comfortably generate ~300-600 lbs of linear force and sufficient travel with a 1/2" or 3/8" master cylinder. I have yet to confirm this, but stock clutch basket takes ~200lbs to compress, with HD clutch springs should take ~400lbs.

[fantino]

A pretty sweet package came in the mail today. Clocks in around 16 lbs, which is a healthy 20-25% reduction from stock crank weight. Great work from APE. Sounds like I'll get my balanced rods back from Mike pretty soon here too. I also decided to add a little something special to the crank a bit later on, I'll probably make the purchase after I get the cam + top end sorted out with Mike.

Head is boxed up to go to Swaintech for coating, just waiting for my OS intake valves to show up so I can send everything off.

In other news, I finally found my aesthetic inspiration for the bike, something I haven't really seen on an SOHC4 yet and from a source I never would have expected. Gonna keep the finer details to myself for a bit, but let's just say I'm 100% back on board with an all composite tank, seat + full-fairing. I will probably look into making the tank + seat myself since I have the know-how and resources. I would also like to custom tailor the laminate which is not really a (feasible) option with most composite tank suppliers. The fairing I will likely purchase as I don't want to invest the time or money into tooling.

[SOHC4 Cafe Racer Fan]

The idea of a composite tank sounds interesting.  Artracing made a carbon fiber fuel tank (check out his replica Bimota build).  Make sure that your resin can withstand use with ethanol based fuels.  There are many horror stories of fiberglass tanks failing when using modern gasoline.

You have a hell of a collection of performance parts.  Looking forward to seeing it come together.

[fantino]

I've been following the Bimota build, really impressive stuff.

I'm a composites engineer by education and trade, and while certainly not an expert at fab work, I do have quite a bit of experience and plenty of resources available. I think this leaves me in a fairly unique situation to really get what I want out of this part of the project.

In regards to modern gas, it's definitely a challenge, but some of the issues I see:

• Laminating resin: most tanks are made with a general purpose laminating epoxy -or- even worse, polyester. This is simply a matter of economics, it's a labor intensive process to build a tank and they don't sell for that much. Using higher end materials really eat into profits and often require additional considerations.
• Service Temp/Postcure: our tanks are on top of hot engines and live at elevated temperatures. When epoxy cures at room temperature, it reaches a state called vitrification where the polymer structure is unable to form any additional crosslinks. This will give the resin a specific glass transition temp (it is actually a range, as epoxy is not crystalline). As the laminate gets warm and reaches the glass transition range, it will see significantly reduced mechanical and chemical properties.
  
  If you raise the temperature above the Tg and bake the part for a few hours, it will allow additional crossklinking, effectively raising the service temperature of your laminate and allowing it to resist solvents and maintain strength at a higher temp. There is obviously a limit to this as eventually maximum cross-linking will occur and at a high enough temperature, you will start degrading the polymer chains.

For now, I plan on using MAX GRE for my laminating resin. It is a Novolac (phenol formaldehyde) based epoxy formulation specifically for resistance to fuel, same as the Caswell coating, but at a better volume price and tailored to laminating. This way my entire tank will be made of what most folks only coat the tank with. Eliminates the chance of a coating disbonding.

I will probably make a sample and submerge it in gas for a month or two to see how it does. If I'm not satisfied, my next course of action is to try a fluoroelastomer coating (viton) on both halves of the tank, joined with a caulk of the same material. This is the same material used in most modern day fuel systems for gaskets and sealants and is *extremely* resistant to modern fuels. It's just a little pricey and I have to get it through work, the few suppliers of these products don't do sales to individuals.

If all else fails, I work next to a marina that sells E-free gas

I also plan to use a combination of carbon and kevlar for the laminate. The kevlar will provide both abrasion resistance and toughness (less brittle/crack prone) in case the bike ends up on its side.

[Tews19]

Did I miss the explanation on the exhaust tip?

[fantino]

I haven't seen any other MGP exhausts with that tip yet. He must be trying something new, I guess.

[Camrector]

Did you weigh your crank before and after APE chopped it? Mine started at 24lbs and came back at 18.5lbs

[fantino]

~20.5 to 16.4.

Is your weight including the charging rotor?