Topic: 1980 CB650 Cafe Racer

[Kurlon]

I just picked up a freebie 1980 CB650 this weekend.  The bike is going to be turned into a cafe racer with emphasis on racing... I plan to campaign it in the USCRA Formula 2 class in addition to using it as a street toy.  I'm going to rig the front and rear light clusters so they are quick detach.  That'll make it so it'll just be a matter of pulling the sidestand and mirrors as well as plopping on my front number plate to run through tech.

My initial review of it was pretty positive for a gift rat, one fork seal needs to be replaced, gas cap is missing, needs a countershaft or shift shaft seal and a good bath.

I stuffed a battery in it last night, put a little gas in, and it fired right up.  Odd whirring sound from the right side, too consistent to be a cam chain?  No rattle to it, almost electric sounding?  Gas tank is totally rotten and leaking from everywhere.  Other than that, and a couple indicator bulbs being out, it's right there.

So, I've got a couple questions on stuff I'm planning on doing...

First, I love the modern swingarm/fork setups I've seen here, in particular the use of Honda bits, sticking with the brand makes sense.  Looks like Honda CBR F3 forks should be a simple adaptation.  I've seen one bike with a CBR swingarm, I'm assuming F4 or earlier, hopefully the chap will chime in with some hints in that thread.  At the same time the frame is getting worked over, lots of scary welds/etc.

I want to rewire the bike from scratch as a worn out 30 year old harness scares the crap out of me.  I see the CB650 uses a different stator setup than I'm used to.  Is it possible to convert back to a traditional magnetized rotor to eliminate the need for brushes/battery voltage for charging?  Anyone make a high output charging system to retrofit to this bike?

I'd also like to upgrade the igniters as mine are pretty crusty looking, the bike had a bad regulator/recitfier in it's past and has cooked them pretty well.  An adjustable setup would be idea, but 'newer' at this point will suffice.  Do I have many options here?

[The_Crippler]

Looks like your picture didn't come through, there.

I'm interested to see your project come together.  I had debated do a racer with mine, but the frame shape and the lack of aftermark parts discouraged me.  There's a lot out there for the 5/750s, but not much for our 650s.  If you're already into the race thing, I'm guessing you'll be a lot more willing to fab stuff than I was.

[Kurlon]

Picasa is being weird.  I'll just host the pic myself and update the link later.

I don't mind the fab work, and I don't care if this isn't a hot contender, I'm more just looking to get something that I can get on the track with.  My prior vintage racebike, a GS500E has been converted back to full street for my wife.  My modern race bike, a KTM 520SX in motard trim needs a complete overhaul before it can be tracked again, and I just bought a house so I've no real budget.  This project is going to depend entirely on what I can scavenge up and do myself.

[The_Crippler]

Pic is there now.  We're good to go.

I will always have an affinity for the GS line, as my first bike was a GS850GL.

[Kurlon]

I loved my GS500, gutless as all hell, but once I redid the suspension it turned and stopped great, was light and an absolute blast to ride like a hooligan, WOT all the time, grabbing gears like a fool, and not really abusing any traffic laws. : )

On the CB650 front, I've verified my tank is a total loss, it's been re-sealed about 7 times with Kreem, and the area around the petcock looks like it has a tumor from all the layers of expoxy and bondo that have been plastered onto it.  I have a friend with a CB400F that says I can try it's tank to see if it'll fit.  I'd love to get that bike revived... motor is completely seized... but thats another project.  Looking at parts fiches, the CB400F tank doesn't look like too difficult an adaptation?

I'm going to try and drag the bike up to a friend and good wrench to get an eval on that odd motor sound I can't ID.  If the motor gets a reasonable bill of health I push forward.  If not, I may abandon the project for now as I've got no real budget to rebuild it... yet.

On the pipe dreaming front I had a ball reading the fuel injection conversion thread.  Brilliant work there.  I just happen to have a 1984? GPZ1100 thats been converted to flat slide carbs, leaving me with a handy set of period correct throttle bodies... hrmmm... : )  I also was impressed with the VFR stator conversion, and would like to do the same to this machine.  Lighter flywheel, more than enough power for EFI, and no brushes to worry about, sounds like a win to me.

It also looks like Dyna's 'ARC-2' CDI might be a good upgrade for the stock ignition?  It'll take the current load off the stock ignitors, and will only draw power to fire the coils when needed rather than keeping 12v on them at all times and collapsing them to fire.  The Dyna 2000 is nice because you can tune it, but it's an inductive system just like stock, which means wasting power especially at lower RPMs.  If they had a version that was a full CDI ala the ARC-2 setup that'd be ideal.

Further pipe dreaming, what is the bore diameter on a CB500 cylinder block with the sleeves out?  I'm class limited to 650cc for Formula 2, so with the stock stroke that caps me at a 61mm bore.  Is the 500's block small enough (56mm bore with sleeves) to open up to 61mm and plate to run without sleeves?  How different are the block heights between the CB500 and CB650?

[cb650]

If your not going to use that front tire and its not weather checked I might be interested in it.

[Kurlon]

I don't plan on using it, DOT code has it as 2003 vintage, it's a bit hard, but no signs of cupping or dryrot when I last looked.

Down side is I can't yank it till I source the replacement front end.  Turns out cheapie CBR F3/F4 front and rear ends aren't really that cheap. : )

[cb650]

No hurry.  Dont need it but I like the qualifiers and they are not made anymore.

[Kurlon]

Anyone know the sprocket offset on Honda CBR F2 and F3 rear wheels?  I've eyeballed the CB650's at a touch over 3 inches.  Just curious if I'm going to need an offset front sprocket to make this conversion work, or if I'm already in the right ballpark.

[traveler]

Welcome!

Looking forward to seeing this build.

I'd recommend buying a titled CB550 frame and using it.  Has a cleaner look for a cafe bike....everything will bolt right in.  The 650 frame is more of a cruiser frame....just my .02

Might be more cost effective to use a GSXR front end, but you want all to stay all "Team Red"....so just have to dig a bit more to get a CBR front end, and might as well get some CBR rearsets and plan on welding them on to the frame.

Verboten on here, mated up a Ninja 600 rear swingarm, and there HAS to be away to go mono shock on that!

Anyhow, congrats!

~Joe

[Kurlon]

If I come across one cheapy cheap I'll consider it, for now this is a run what ya 'brung or stole project. : )

On the list of things to consider acquiring now - 95 to 97 ZX6 front and rear ends...

[Kurlon]

Motor got a clean bill of health, other than cam chain noise.  Going to try letting the tensioner adjust itself to see if that cleans it up.

So now, I need to get seals for the shift shaft and countershaft, as well as source a tank so the bike can at least be ridden as is.

[traveler]

Well, that's good news!

~Joe

[Kurlon]

Worked on the tank today, all sorts of epoxy on the bottom around the petcock.  It was almost rubberized after all the exposure to gas and peeled off, it didn't even take the paint off?!  I found the petcock nut was loose, and the seal wasn't in properly.  Maybe I lucked out?  Re-did the seal, tightened things up, added gas...

That wasn't the leak.  The problem is a hairline crack around the petcock spigot tube where it meets the bottom of the tank.

Can that be welded or am I SOL on this tank?

[Frankenkit]

It can be welded, I'm pretty sure.

If you have no specific attachment to that sissy bar, I would be interested in using it for my summer trips... all my gear wants to slide off the back at 70 mph...

Tony at oregonmotorcycleparts made my regulator/rectifier and I really like it.
be forewarned that if your igniters and r/r are cooked you may have issues with your rotor... just check resistance (with everything together if possible) between the black and white leads and make sure it's durn close to 5.5.  Even if it checks out, you might still have a dead or dying stator.  They're one of the things that goes bad on these bikes.  The more direct way to check the rotor is to take off the alternator cover (the one under the left case guard) and test right on the sliprings.  Brushes can go bad, too, and they're way cheaper than a rewound rotor, but cross those bridges when you come to them.  Tim Parrott (tpe enterprises) rewound mine and it's pretty slick.

[Kurlon]

Ok, so now the tires AND KG rack are spoken for... hey waitaminute?!  This wasn't a parting out thread! : )

So yeah, you've got dibs on it.  Be warned, I'm likely going to charge some miniscule fee to try and cover some of the build costs on this thing. : )

Plan for today is to get a wire brush wheel for my drill and see just how bad the metal is on the bottom of this tank.  Might also get some rough dimensions and pics of the back end for plotting a swingarm swap.  The length is approx 22" which matches up with a CBR F3 unit so it looks like that swap can't degrade the handling any.  I'm kinda curious if there is room to do a monoshock conversion... maybe if I toss the airbox...

Edit: Forgot to note, cam chain noise is gone, the automatic adjuster still has some life in it I guess.

[cb650]

I was just going to ask about the rack too.   I have one though with the locking/removable trunk.

[Kurlon]

There is a complete 1982 CB650 at a salvage yard in Auburn ME, has a rack with bags and top case, and supposedly runs.  They want $800 for it.  Saw one a bit more beat up than mine in back for $500.

In other news, cleaned the tank with a wire wheel around the petcock and saw a ring of obviously different metal where the spigot meets the tank... solder?  I know how to do that!  I hit up the local hardware store for a propane torch, rosin and silver solder and made a repair... holds beautifully!  Now all I need is a gas cap and I can try running it up and down the road!

[Frankenkit]

woohoo!

[The_Crippler]

There is a complete 1982 CB650 at a salvage yard in Auburn ME, has a rack with bags and top case, and supposedly runs.  They want $800 for it.  Saw one a bit more beat up than mine in back for $500.

Dude:  Buy them both.  I really wish there was a salvage yard close to me.  (You'd think there would be.)

Tony at oregonmotorcycleparts made my regulator/rectifier and I really like it.

Was yours a needed replacement, or something to improve over stock?  (I need to digitize your brain and market it as an E-Manual for these bikes.)

[Frankenkit]

Oh gawd, Crippler... what's that smell?
It smells like too-much-credit! 

Mine was just bought as a last-ditch effort to improve my charging, but I HAD to rewind the rotor. It was internally shorting when hot.

[The_Crippler]

Oh gawd, Crippler... what's that smell?
It smells like too-much-credit! 

Mine was just bought as a last-ditch effort to improve my charging, but I HAD to rewind the rotor. It was internally shorting when hot.

What can I say?  You're one of my first go-toos for 650s.

I had wondered because I know these bikes have electrical issues, and didn't if it is something that I (and the rest of us with these) should invest in and preemptively replace.

[Frankenkit]

see... there are two ways of thinking about it:  If you get a new one right away, you can be relatively sure it'll be working fine.

If you test the old one and it checks out ok, it'll either work well for you until it doesn't or it'll be shot and somehow still testing out ok. 

If you'd rather shell out for the relative assurance, or wait and see if it works well for you forever, the primary difference is money.  ...but tim parrott's hot-wound rotor has me charging at 14v at 2k rpms.

[Kurlon]

Did some playing around today, tank is full of fresh gas, dry gas, and Techron.  If anything is going to eat it's way out and expose weak points, that combo will.  : )

I poped the countershaft cover off to see if I can discern where the leaks are, what an oily/icky mess.  The prior owner was a bit... liberal with chain lube so that's gumming up the works.  I can see fresh motor oil in there too.  There isn't an obvious leak point though which is annoying.  I'm hoping it isn't the oil pump as I see at least one o-ring is discontinued...  Can the oil pan be dropped with the motor in the bike?  I'm half tempted to believe it's the gasket failing on one side that's part of the problem given how wet the pan is.

Played with the carbs a bit, either the floats are set way low, or they aren't filling properly.  I've got plenty of flow out of the petcock it appears, but I only get a trickle out of the bowl drains.  If the bike is off choke it dies.  Let it sit for a second and hit it and it'll hold an idle for a moment before dying like it's out of gas.  With the choke once warmed up it'll hold 3500 to 4000 RPM sustained, so maybe the floats aren't THAT low?  Right side exhaust is loading up a bit too, I can't hear a miss but I can see a puddle under it at the joint so something's not kosher in one of those two cylinders...

[Frankenkit]

Can the oil pan be dropped with the motor in the bike?  I'm half tempted to believe it's the gasket failing on one side that's part of the problem given how wet the pan is.

If the bike is off choke it dies.  Let it sit for a second and hit it and it'll hold an idle for a moment before dying like it's out of gas.  With the choke once warmed up it'll hold 3500 to 4000 RPM sustained[...]

You can drop the sump but you may need to remove the exhausts first, and you will definitely want to use new bolts, because these seem to like to snap off and they're a real, real mother to drill out.

These bikes, with the stock carbs, are extremely lean on the idle circuit, and because of the press-in idle jets, this isn't really very adjustable.  I usually leave my choke at least 1/4 to 1/2 out for the first half mile.