CB500 - 600cc Henry Abe build

[brycegp]

So here goes. This is my first motor build and I'm going all in. I love the CB500 so I decided to start with a hot motor and later build a bike around it.

I scored a $50 motor from CL which I am using as a platform. At this point, I only have the original motor so I started breaking it down. I am hoping that the internal hardware is all salvageable. So commence break down of top end...

 

[VonYinzer]

Im in... Keep it up.

 

[crazypj]

500 is a nice motor but you would have been better off with a 550 as it has modified transmission with a dedicated oil pump.
Gearbox shafts are a little stronger and clutch operation is different (inner pressure plate instead of external pressure plate.
They both have same issue if you try and fit 'O' ring chain (it 'eats' case around seal/bearing)
They both destroy main oil gallery if primary chain gets loose through wear (no tensioner, 400F is better in that area, and uses same primary chain as 500/550)
Oil pressure switches fail pretty regular if you use anything other than 10w/40, I still think it's a stupid idea to have pressure switch mounted on oil pump where it 'sees' 70~80 psi at start up
Main galley would be a better place (but may be 'scary' if oil light doesn't go out for a few seconds)
Kit is probably 591cc (61mm pistons?) although its marketed as 590, 600 and 605 :
You need liners for 500, 550 can be bored to fit 61mm pistons. (I did mine in '78 or '79, forget which ;D )
Cam and exhaust is a good idea,I have cam specs for mine somewhere 'safe' I find cam sheet ever few years I'll see if I can find it (mine was around 130 'touring' 8) )
Oh, it's a good idea to counter-bore the recess in the ends of cylinder, fit a dowel and slightly larger diameter 'O' ring, prevents the leak that happens every few thousand miles (another mod I did to mine )

 

[brycegp]

I just recieved a CB650 SOHC camshaft that I found on Ebay. When I got the cam, I imediately noticed that the sprocket on the cam is correct for a 650, but when I started comparing the cams side-by-side with my 72 500/4, it appears they are both identical aside from a casting identifier.

How similar are the grinds between the 650 and 500/550? Any shade-tree way for me to compare them?

Can anyone tell me how to measure it to verify its a CB650 cam??

I have a basic multimeter and its not very exact...but as close as I can tell here are my measurements.

CB650 CUSTOM Cam
Base Circle: 28mm or 1.10"
Cycliner #4
IN: 35.6mm or 1.40"
EX: 35.2mm or 1.38"

CB500 Cam
Base Circle: 28mm or 1.10"
Cylinder #4
IN: 35mm or 1.38"
EX: 34.5mm or 1.36

These differences seem barely worth mentioning. Is this seriously enough to make a real HP increase?

 

[dcmspikes]

im in to watch this happen. good luck sir

 

[crazypj]

You need to check over at SOHC4 about cam.
It doesn't sound right though

 

[brycegp]

I am skirting the cam issue for now till I get clearer answers...but all "hot" cam is in my this motor's future.

But I continued breaking down the motor to get a look at what I am dealing with. And aside from old oil...this baby looks pretty clean. But then again...this is my first rebuild so you tell ME...how's she looking??

 

[Sonreir]

The bottom of the case should tell you most of what you need to know... any metal filings? Also.. piston and sleeve wear shouldn't be a major concern since you're boring it out, but it doesn't hurt to check anyway. Pay special attention to the cam journals on both the head and the rocker cover.

 

[brycegp]

here is the response from SOHC4 guys on my cam measurements. I'll proceed with this cb650 cam. pics of it coming shortly.

Scott - do those lift numbers look close??

Yes, that's about what's listed in the previous post. Remember, multiply that by 1.1 (rocker arm ratio) to get the full lift. The 650 cam is sorta like a "hot street" cam that an aftermarket supplier would offer. There are some specs in that link I posted earlier that you could compare it to.
You'll need the tach drive for the 650 and a 650 or 750 tach.

 

[crazypj]

You need to pull primary shaft and chain to check the oil way underneath (chain gets loose and wears through alloy into it)

 

[scotch]

http://www.sohc4.net/?p=333 i found a ton of info here about the 550/650 engines.

 

[brycegp]

thanks scotch! that link is very informative! I'm not going hybrid except for the cam but its nice to read up and get familiar for general knowledge. who knows what I'll end up doing before its all over...

 

[scotch]

i'll definately be following your engine build. i've got a 550 that i'm looking to hop up a bit and the news that a 650 cam is like a mild street cam is good news for me. that's a lot more accessable to me than a mega cycle cam or for over 300$.

 

[Tetter]

Hey Brycegp, not sure I read correct.
Are you going for an oversize bore ?
I'm thinking of mounting a CB650 cam and CB750 carbs on a for the rest stock CB500 engine........

 

[brycegp]

Hey Brycegp, not sure I read correct.
Are you going for an oversize bore ?

yes...going up to 600cc.

 

[brycegp]

Ok...finally getting back around to this build after being out of town for a lot of last year. Anyway...disassembly is nearly complete finally. The last step is to remove the Cylinder Studs from the bottom case. I need a tip here. The studs don't have any way to grip them...no flat surfaces to put a wrench on or anything. Putting a vise grip on them could score them up and I'd prefer not to do that unless absolutely last resort.

Suggestions?

 

[brycegp]

Its all apart and ready for inspection and clean up. Except for the cylinder studs are mentioned above...