Topic: 1982 CB650SC, Project: "Black and Blue"

[tourmax]

That's not too tiny, I've got an old green Harbor Freight from the 80's, 7x10 is an exaggeration. Old machines just make me happy.

I bought mine used (obviously) and it was almost something I settled for. I would have preferred to have a 12 " atlas/craftsman as I find I'm often just a bit too big for the 10", but metal lathes in general are difficult to find here. There's also the fact that the 10", being more common than the 12", is easier to find parts and tooling for it.

[tourmax]

Snagged a set of 82 CB650 cylinders off ebay for 20 bucks. A couple dented fins, one chuck missing and the bores have seen better days:





Not a big deal. I can heat and strighted the bent fins, Tig in new metal for the missing chunk and planning a 61-62 mm overbore.

Now to keep an eye out for some "affordable" 77-78 CB750F pistons.....

[tourmax]

OK, seems the sickness is taking hold. Picked up a set of used cylinders from a CB750 sohc and am now shopping for pistons to kit out the 626 to something a little....."bigger". The sleeves are rusty in the block, but I'll be boring them out anyways so a little surface pitting just means a better purchase price for me.

But with bigger bores and different flame propagation properties, I'm a little concerned about using the fixed ignition curve from the stock ignitors. I'm considering adding a TCIP4from ignitech.

Or possibly, depending on how long it takes for the wife to get the antidote for "modditus" to me, fuel injection.....which ignitech also offers.

Yes, I'm a fan of Ignitech. I have a tcip4 on y 89 FJ1200 and my Venture/Vmax 1200. Having full 3d control over the Ign curve is jammy, but it also is how I was able to add vboost to the Venture as it will also control things like the vboost servo, an EXUP valve and many other options. Anyways, I;m not trying to sell them, so I'll cut the "fanboy" paragraph off here.

[tourmax]

Well, the rear wheel is now “centerlined”:



Only problem is its hard up against the swingarm on the left. What I’ll have to do is shave more off the carrier. That means there won’t be enough left to hold the axle seal. Its not ideal to drop the seal, but the wheel bearings are also double sealed (part of their design) and the bike isn’t going to be used much (definitely not in bad weather) so its an acceptable compromise.

[Alan F.]

I agree, I had to replace a seal with a spacer once, I just added a loose o-ring and some grease to add a little protection to the sealed bearing.

[Stev-o]

Evapo-Rust is a great product to use on your tank.  You may not need to line it afterward unless there are pinholes?

https://www.amazon.com/Evapo-Rust-Original-Water-based-Non-Toxic-Biodegradable/dp/B00GRSOJSS/ref=asc_df_B00GRSOJSS/?tag=hyprod-20&linkCode=df0&hvadid=312151579877&hvpos=&hvnetw=g&hvrand=11672802779651265198&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9028253&hvtargid=pla-499804341797&psc=1

[tourmax]

Evapo-Rust is a great product to use on your tank.  You may not need to line it afterward unless there are pinholes?

https://www.amazon.com/Evapo-Rust-Original-Water-based-Non-Toxic-Biodegradable/dp/B00GRSOJSS/ref=asc_df_B00GRSOJSS/?tag=hyprod-20&linkCode=df0&hvadid=312151579877&hvpos=&hvnetw=g&hvrand=11672802779651265198&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9028253&hvtargid=pla-499804341797&psc=1

Yep. Already have a jug sitting int he shop, waiting......

[Kelly E]

After you get done with the EvapoRust rinse the tank with diesel not water. Pour the diesel in and shake the tank. Pour out the diesel and the sludge will settle quickly. You can pour the diesel back in for another round of shaking and dump the sludge. I rinse several times to make sure I got all of the EvapoRust out. The diesel will coat the tank preventing flash rust and dilutes into the gas with no issues.
I just don't have the heart to put water in a freshly de-rusted gas tank.

[tourmax]

After you get done with the EvapoRust rinse the tank with diesel not water. Pour the diesel in and shake the tank. Pour out the diesel and the sludge will settle quickly. You can pour the diesel back in for another round of shaking and dump the sludge. I rinse several times to make sure I got all of the EvapoRust out. The diesel will coat the tank preventing flash rust and dilutes into the gas with no issues.
I just don't have the heart to put water in a freshly de-rusted gas tank.

I usually use MEK for final rinse before coating.....

[tourmax]

Ok, so some (most?) on the board know a set of 85-88 zx600 carbs slip right on to the CV CB650 head. But those are getting kind old and hard to find these days. 89+ carbs are much easier to find, but they are 36 mm throats (85-89 32mm) and they are a "semi downdraft" style carb while the 85-88 are sidedraft.

SO, I've got a low bid in on a set of 89 600 carbs to see if I can adapt them to the cb650 cv head:



I may pick up a spare head so I don't have to cut on the one from the bike. I usually prefer to pick up a "distressed" part when I go chopping things up, just so I don't ruin the original and have to go looking for a replacement.

It sure looks like the frame backbone is in the way of "kicking up" the carbs to get the float bowls level. If it doesn't clear the frame, I'll look into "clearancing" it. I've been wanting to make some frame mods between the swingarm pivot and the steering head, so it might be a good reason to have a go at it. I never have liked the "stamped and welded" scheme Honda used for these frames. Not to mention, they literally LOOK like flexi flyers with the stock frame.

There's also the concern of whether or not they will fit under the tank with the kick up they have. I can clearance the tank, but I'd really rather not do that if I don't have to.

I'm not even sure if the intake tract can be properly modified to utilize the downdraft carbs.

But, what the heck? I'm willing to give it a try.

I gotta be shaping metal on a regular basis or I get pretty bored. this should keep me busy for a while......


Edit: the more I think about it, the more I'm thinking I might give the downdrafts a pass....

[Ramrod_Racing]

I got really lucky when I picked up a set of ZX carbs because I didn't know that they were going to fit and was pleasantly surprised. I believe that the early ZX carbs were the same ones used on the later GPz 550's, so maybe there's a few more to be found with some broadened search terms.

[tourmax]

Yep, pulled my offer on the downdraft carbs. Just too many hurdles to overcome.

Back on the hunt for some 85-88 side draft zx600R carbs. A set will show up sooner or later....

[tourmax]

Muffler round about where it will end up:



Yep, I really like that! Gives it a bit of visual “chunkiness”.

Obviously, I’m not going the “whack everything off and sit on a board” cafe look….lol!

Thats probably not the final placement, its just hanging there so I can get a quick visual of what it will look like. I’m thinking it might move forward around 2-4 inches and down enough to be inline with the rest of the exhaust.

But I’m liking it so far!

[Gurp]

I am absolutely loving this project... Everything about it.
Love those square lights naked. That's a awesome look? What are the off of?
Really though with the double seal bearings even with some weather you should be in great shape regardless.
Seeing all this great precision work begs to ask....
What do you do for a living? This are definitely not a common set of skills.

[tourmax]

I am absolutely loving this project... Everything about it.
Love those square lights naked. That's a awesome look? What are the off of?
Really though with the double seal bearings even with some weather you should be in great shape regardless.
Seeing all this great precision work begs to ask....
What do you do for a living? This are definitely not a common set of skills.

Lights are off a cbx750f. I bought them a long time ago in the uk. The cbx wasn’t offered in north America.

I’m retired. Was military, search and rescue, 30 years.

But, I’ve been a gearhead since about age 9. All skills I’ve picked up over a lifetime of wrenching.

[tourmax]

At the point where I need rubber on the rim (clearances, spacing, alignments, etc) so I spooned on an old worn out 170/60:





Man, that tire looks even fatter on the big than it actually is. Probably also has something to do with the fact the tire is essentially “flat” across the center from drag racing….

[Alan F.]

Sure does look good with its sneakers on.

[tourmax]

Going coil on plug, coils from a cbr600. the Ignitech box will run them just fine and instead of wasted spark, it will run them sequentially.

Mechanical advance will be disabled, the Ignitech will run the spark advance digitally and I'll be able to add or pull timing wherever I want on the map instead of a fixed advance that you get with the mechanical system.

Not to mention (if I want them) programmable rev limiter, launch control, shift light and a dizzying amount of other options.

Gotta love modern electronics.....peps an old girl right up!

[tourmax]

Got my eye on a set of used .25 over cb750 pistons. That would take it out to approx 657 cc’s….that should give it just a little more “punch” than the stock 626 cc’s. IIRC, the bike used to puff a little blue anyways, so punching it out a bit isn’t that bad of an idea.

The 750 liners will go on the shelves until I cone across a decently priced 836 piston set…

[tourmax]

Well, damn the torpedoes! I’m going in!

Decided to take the risk and grabbed a fistful of used cb750 dohc pistons and we’ll see how it goes I can machine them in my home shop, so lots of development time available at the low low cost of my time.

If it works, should kick the cc’s out to 657.

I’m also following a couple used sets of cb900 dohc pistons. They’re 64.5 mm and should punch it out to 729 cc’s with the use of some cb750 sleeves in the cb650 block….

[tourmax]

Decided to change the switchgear to something a little more useful/modern:

[tourmax]

Well, screw it:



chevrolet 0 60

98 zx600r semi downdraft carbs. Couldn't turn them up at 134 cad to my door. I did a couple quick photochops with the downdrafts and a CB650SC image. Looks like they will fit, but airfilters/airbox is going to be an issue. I'm thinking I'll get around it by designing my own airbox in 3d and printing it off in abs.

There's also the issue of the sidedraft 650 head and tilted 600r carbs to work out. I'll be modifying the intake tract, not the carbs. No real way to modify the carbs anyways and the head may benefit from a "straightened" path, as long as I can make it a smooth transition.

Eeehhhhhhh....what have I gotten myself into?

At least the 36mm carbs will better feed the 657 at high rpms.....we'll see what happens with the rest of the rpm range. It may be "overcarb'd", but only way to know is to try it....

[tourmax]

hmmm, picked up a set of intake "boots" for the zx6r carbs:



Looking at those, I might be able to just machine off the OEM 650 head intake posts, create a flat sealing surface and bolt them on.....

[Kelly E]

We put Mikuni RS 36mm carbs on our 80' Suzuki GS 1100 and I was worried that it will be overcarbed. Seems like a lot for an SOHC 650cc motor. Hopefully it works.

[tourmax]

We put Mikuni RS 36mm carbs on our 80' Suzuki GS 1100 and I was worried that it will be overcarbed. Seems like a lot for an SOHC 650cc motor. Hopefully it works.

Yup, its a concern for sure. Theres at least one 650 on the board running 85-88 zx carbs and those are 32’s.

Biggest concern is the air velocity in the Venturi and not pulling the right amount of fuel, but I have a few “tricks” to try if it becomes a problem.