Topic: 1975 CBB550 build- very first bike and first build

[calj737]

the 59m kit Bootsey linked is probably a better bet. Nothing wrong with 600cc, but to really gain some benefits from it, cam swaps and some better valve train work are recommended. If you want to refresh and wake the motor up, the 59s with some fresh valves and a strong state of tune will make the bike quite happy, and very spry.

If you want a little street beast, then check out the recipe flatlander used on his bike and got about a 25% HP bump from 59s. His motor has quite a bit of $$ in it, but it does show the balance between air flow and displacement. These motors really like to breathe and can be coaxed into some pretty good power with top end work.

[SOHC4 Cafe Racer Fan]

The stock heads on the 500/550/750 all benefit greatly from porting work.

If budget is a concern, you may want to stick with the 59mm kit.

[CBertels]

Thanks everyone for all the advice.  I'm trying to do as much research as a I can on the forums and elsewhere to avoid asking the same questions you've all seen a million times.  I'm hoping to get the engine out tomorrow and get the top end to the machine shop.  I'll make the decision on bore size once I get an idea what shape the cylinder and head is in.  PO said the head had "work' done already, so I can't wait to see that that exactly entails...

I like the sound of the street beast Cal described    I read through Flatlander's build and its really impressive.  With this build I'm more concerned with simplicity than cost.  I wanted to avoid anything too exotic or difficult to source.

Now, once I dig into the 750 and get thoroughly over my head, I'll be looking and going overboard.

[madmtnmotors]

With this build I'm more concerned with simplicity than cost.  I wanted to avoid anything too exotic or difficult to source.

That's a good plan. The bigger the overbore the more stress on other components. If the 59mm pistons will work that sounds like a sensible performance modification, without breaking the bank, and leaving room for future expansion (61.5mm) if the spirit moves you... 

[Restoration Fan]

you;; have another chance, I'll be in Orlando (again) 9/8-9/12. Between the 3 of us, we should be able to coax at least 60HP out of this little monster and get it running in about 6 hours?  I'll plop my 500 motor in it, bring my extra MotoGadget m-gear and we'll have some fun!

Wait, what?  Atlanta is on the way to Orlando, right???!!!!

I mean, I have TWO 550/500's to do and you didn't offer help with those.  Geesh.  I see how it is now! 

[calj737]

Atlanta is if I drive down 85. I've been taking 95 due to time constraints. I owe Bill and you a visit. I'm heading back down to Orlando M-Th of next week again 

[SOHC4 Cafe Racer Fan]

Cal,

You must log some serious miles in your work. 

[Restoration Fan]

Atlanta is if I drive down 85. I've been taking 95 due to time constraints. I owe Bill and you a visit. I'm heading back down to Orlando M-Th of next week again 

Well, if you're ever looking to break the drive up and not drive the whole thing in one day, you're more than welcome to stop here & spend the night.  I have a pretty big house with an extra guest suite that's got your name on it. 

If you're really nice, I might even let you ride a real motorcycle...errr, I mean a 750 named Stella! 

[calj737]

Cal,
You must log some serious miles in your work.

I didn't put 500k on my S500 in under a decade because it sits in a garage! Hell, even the S65 has 200k and I never drive it. Plus my F-250 has 225k... See now why I build my motors the way I do? If it can't go 300k I don't want it-

Even my 2 BMW K bikes each had over 200k on them. The K75 I did that in under 4 years. The K100 took about 6 years (I was slacking a bit then and flying internationally a lot).

[Restoration Fan]

Besides your job as an international studmuffin, what else do you do for a living, Cal?

[calj737]

Victoria's Secret Runway model. Takes up way too much time!

[SOHC4 Cafe Racer Fan]

Shhhh.  Cal is an interstate man of mystery!! 

[CBertels]

inally got some free time and tore down the engine a bit. Lots of strange things on this one so I'll try to go in order.

While removing the carbs and exhaust, the bolts on the exhaust and intake manifold were quite loose, although maybe a blessing.

The cam cover and the rockers all looked pretty good. No noticeable scoring/wear and moved freely without any noticeable side play. The cover, however, had some large holes that appear to be some modification from the PO. Photos below. Two are on one side, one on the other. Is that normal??

In removing the head, this is where stuff got interesting. The alleged port/polish job is concerning. The "football" in both the intake and exhaust ports have been ground down quite a lot compared to photos I've seen of stock. Inspected the ports looking for obvious problem signs. I believe the valves have been replaced and not properly. Two of the intake valves are not completely seated and I can see a flashlight shine behind them. No trouble with the exhaust side that I can see.

The cylinder block looks freshly machined or honed and feels very smooth. Very clean and I could detect few wear marks or grooves. There is a small corner of a fin that broke off that I didn't notice when assembled. Can this be easily repaired?

The piston tops were to very clean. . The tops of two look almost brand new while the others look marginally worse.  A good sign I guess. I did find a broken ring, but I'm not sure if that happened during disassembly or was broken in the cylinder.

 I'm betting whomever did the "rebuild" never got it running once reassembled. The gasket between head/cylinder looked very new and a bit thick (1.25?) while the one between the cylinder crankcase much older and stuck to the cylinder.

I'm gonna check with the recommended machine shops for the cylinders and will have that head looked at as well.

EDIT: Photos are not uploading at the moment, but I'll get some up soon.

[CBertels]

Photos of Cam cover.  Hole are towards the top.  Should these be here?

[CBertels]

Example of porting.  Both intake and exhaust look pretty similar.

[CBertels]

Shot of the valves.

[CBertels]

Head and cylinder:

[calj737]

If it were me, I'd be looking for a new head. And there is zero indication of a recent hone on the cylinders, which may be a good thing. Smooth is a great objective, but, one of the pictures clearly shows vertical scoring (however slight) and that is proof that no recent hone was done and needs to be.

Have the cylinders and corresponding piston measured by a machine shop. If they are within spec, have them rigid honed and install new rings. But I'd replace the head. A porting job performed by someone who doesn't know what they're doing (in this case) causes more damage than not having porting done at all. It is my impression from the pictures, that none of the ports is equal to another and now you will have a terrible imbalance in combustion. And some of the valve seats look badly out of center where the edge of the valve is protruding out of the chamber pocket.

So enough about what's wrong, probably not worth fixing. I'm heading to town tonight, and if you ring me up, I'll hand you over a perfectly usable head (needs new exhaust guides and freshening up of the valve seats) and you can hand that over to the shop for minimal expense to get it milled flat and valves lapped/seats recut. This will be your best value and greatest potential for a healthy running motor.

[CBertels]

Thanks Cal!  Now go back to bed! 

I sent you a PM with contact info. Let me know when you're in town.

[SOHC4 Cafe Racer Fan]

 

Yeah, that head looks a little funky.  Go with Cal's.

[CBertels]

That head is comically bad. Every time I look at it I find something else. Found this near one of the head bolts. Any ideas what this might be. Has three tiny prongs on it facing inwards and is about dime-sized.

[madmtnmotors]

That head is comically bad. Every time I look at it I find something else. Found this near one of the head bolts. Any ideas what this might be. Has three tiny prongs on it facing inwards and is about dime-sized.

Looks like a wayward spark plug washer.

[CBertels]

That's what I thought but it wouldn't quite fit. Oh well.

So with all the less-than-stellar things I've found so far, any thoughts on opening up the bottom end?  The PO said they didn't do anything to it, but I still wonder. I plan to yank it out to clean up the frame, paint etc. but didn't plan to crack it open.

[SOHC4 Cafe Racer Fan]

If you've found stray washers about the engine, it would be a good idea to inspect the lower end.  At a minimum, remove the pan and oil pump and screen and visually inspect the bottom end for any apparent damage or bits and pieces of metal.  I personally would do a complete tear down since you don't know what the cowboy prior owner did to the engine.

[CBertels]

Gotten the bike stripped down a bit more over the weekend.  Still need to remove the wheels and front end, but I need to find something to support the bike underneath first. 

I'm going to remove the last of the engine as well but still debating how to go about it.  I've heard others have had success by laying it on its side and lifting the frame off.  I've also heard others have just lifted the engine out.  Since I have just the bottom end left, I'm wondering how heavy it will be.  Any recommendations?

Here's how it sits for now: