Topic: CB650 Engine tune-up for street legal racer

[DresdaHonda]

I have a Dresda frame, ( Classic racing, back in the days) the engine was a tune CB550 engine, built in holland.
Now I want the bike on the street, with a "tune-up" CB650 engine.
At my local honda workshop there is allot of CB650 engines on the shelves.
My question is, is there any  year of favorite to look for ?
My coal is, getting a engine that is easy to gets parts to, with a std, (or easy to come by), Head gasket !!
The engine set up:  ported  top,  lager valves, heavy springs. Wiseco pistons in 61 mm (or easy to come by)think 61 mm is max for the std. head gasket.
-Mayby balanced crank etc., if I can find a workshop here in Denmark
I think I've read that the early CB650 (1979-mid 1980) have an advantage over the later, but what ?
Hope you can help me picking a CB650 engine, for tuning. Br Peter Ravn

[Kemp]

Great Choice! In Canada/USA there are a lot of options for the CB650 engine. The best years are 1979-80 as they used throttle body carbs with the same carb spacing as the CB750 so easy to go with bigger carbs as lots of options including CRs of course. Dynoman offers an overbore forged piston kit complete with head gst, rings, wrist pins that takes the 623CC engine out to 674CC. You can leave the stock cam as it's not bad or use any cam made for the CB550 for more urge. I have a 650 stuffed in the 550 frame and just love the extra performance a simple engine swap afforded. The 650 is basically an upgraded CB550, better clutch, better ignition, bigger alternator, supported primary chain, much improved cylinder head etc. I still love the 550 motor but if you are starting from scratch and have access to the 650...why not..no down side

[DresdaHonda]

So is Dynoman the only supplier of performance piston for the CB650
Like the idea, that I can use a std. head gasket, -so max 61 mm pistons (I think)

[CBGhia]

There is one other big bore kit for the 650, that I know of, but it only increases displacement a bit, not compression. 

http://www.ebay.com/itm/79-82-HONDA-CB650-1-00mm-OVERSIZE-PISTONS-SET-4-PISTONS-INCLUDE-CI-CB650APS-2-/161856493778?hash=item25af6618d2:g:2E8AAOSwmrlUwKfJ&vxp=mtr 

Other people have tried pistons from this guy in 750s and 550s. I have not really heard anything negative except that there is no compression gain.

[SOHC4 Cafe Racer Fan]

So is Dynoman the only supplier of performance piston for the CB650
Like the idea, that I can use a std. head gasket, -so max 61 mm pistons (I think)

Dynoman's kit has 62mm pistons.  That's the outer limit for stock sleeves.  http://www.dynomanperformance.com/engine/pistons/dp-CB550.html

DaveBarbier and I are both building motors with this kit, Mike Rieck Stage 2.5 head and a performance cam.  I am using a Megacycle 126-20 cam (no clearance issues).  I, too would recommend using a 1979 or 1980 head to give you additional carburetor options.

Deck your mating surfaces.

As for headers, I would recommend going through Kemp (see above) at Ripple Rock Racers who can set you up with a stainless Hindle 4-2-1.  www.ripplerockracers.com/

Mike's Porting/Polishing Work





Exhaust ports



Intake ports

[DresdaHonda]

Thanks, I look for the early CB650 engine
Very nice job on that cyl. head.
About piston: (I still like to go with 61mm)
-Is it a lot of work to make the CB750K piston fit the CB650 ?

[DresdaHonda]

Is that black diamond valves ? Looking great
Thinking of the idea with the 61 mm CB750 pistons, model K with mid dome, and then work in the pistons, but is that possible with cast pistons ?
Mayby Im way out of line here, but -I like to go for the 61 mm (headgasket for les than 87 usd) !

[gschuld]

Cometic can make you any gasket you want, in copper, for under 87 bucks.  Ive bough a number of custom gasIets lately from them.  They should have the pattern for a 650 cylinder/head.  I don't think gasket availability should be much of an issue considering the overall expense of the project.

George

[DresdaHonda]

Well, mayby not, but nice to here about costum gasket, for a fare price.
Back to the 1979 -1980 CB650 head,
-please fill me in with some measurement, from cab to cab spacing,

[bwaller]

The CB750K piston will lack dome. I use copper for a head gasket in a race engine, but I personally don't like them on the street. There will always be some oil weeping. Great for compression, not so for sealing. For the street better with MLS and flat surfaces.

[SOHC4 Cafe Racer Fan]

The CB750K piston will lack dome. I use copper for a head gasket in a race engine, but I personally don't like them on the street. There will always be some oil weeping. Great for compression, not so for sealing. For the street better with MLS and flat surfaces.

I can attest to this.  My 750 was initially fit with a copper gasket and it weeped and weeped and weeped.  I switched to HD studs, MLS gasket and decked surfaces. 

There are all kinds of options available to you.  The 750 pistons AND the cruzinimage ebay pistons will only offer normal compression.  The Dynoman kit will up the compression to 10.5:1.  The kit is pricier than the cruzinimage but comes with nice domed pistons and the gasket.

[DresdaHonda]

About lack of dome on the CB750 pistons, there is 2 dome height -the 1969-1976 dome height and the 1977-1978 dome height
Take a look at this page about piston kit: http://www.cyclexchange.net/Engine%20Parts%20Page%20Pistons.htm

[bwaller]

Yes the 392's & 410's have a slight dome. The compression height will be greater than the 650 piston too, so use them if you choose. Be prepared to do lots of assembly/diassembly/measuring to be certain about clearance and to calculate compression...but those are things that should be done anyway.There are thinner or thicker gasket options available to help.

[DresdaHonda]

Now I jump a little in the subject
Thanks for the info bwaller (to much work for me !) and after having looked for pistons, (and its limited) ! 
Performance pistons or no name pistons !
So back to the garage, -. I have 4 CB550 engines on the shelf !.
3 of them I bought for parts
The race engine (built in Holland, not by me) is made with some CB650 parts, (am not sure, but some gearbox parts to make a CR) 60 mm pistons and a ported CB550 cylinder head with o-rings as the cylinder head gasket. The engine was overheating and burning a valve. the pistons look fine, I am not sure where to start, a "racer" CB550 engine, -back to a street engine or a std CB650 engine ?
The main thing is for this project, if I go all the way, with 600 usd pistons, I need to balance the crank, and performance valves and heavy springs, and mayby some performance ign. that's not what I'm in to right now, (dream on)
But the idea to make a CB550 engine with a CB650 head, is more in to my kind of money. This is what I have:

[bwaller]

I'm not sure what the guy used for o-rings but they're on the "large" size! Most, myself included, cut a 0.08-1.0mm groove and use SS wire in the cylinder sleeve flange with a copper gasket.

You use the 650 head with stock 650 valves, choose whatever camshaft, even the 650 piece with a 550 cam sprocket, and just have to select pistons to work with that larger chamber. Dynoman has those designed to work already.

[SOHC4 Cafe Racer Fan]

You can make more power cheaper with a 650 motor.  You can bolt one straight in with no mods, or if you want a bump:
(1) Cruzinimage kit -- cheap displacement increase at approx. stock compression (a nice little bump in hp/torque);
(2) Dynoman 674 kit -- higher compression and better performance but slightly pricier (no clearance issues to the valves!);
(3) Megacycle 126-20 cam -- again no clearance issues;
(4) ported head -- the 650 head already flows more efficiently than a 550 or 750 head (according to Mike Rieck), but you can improve it even further; and
(5) Paulages build -- larger overbore pistons in a 650 (requires very skilled machining, since the sleeves will overlap one another).

I think that depending on how much you want to spend, you can improve your 550 performance simply with using a 650 engine and then add these progressive mods as your budget and tolerance permit.

[DresdaHonda]

Thanks guys, about my CB550 cylinder head, its made  for very large rubber o-rings !
I will now try to find a CB650 cylinder head, (and studs) and work my way from what I have.
I have a set Keihin 26mm, (75mm between inlet holes). Don't know if the rack fits the CB650 cylinder head ?
and I have some loss Keihin 29 mm, from the old "race" engine. let see how "performance this engine is gonna be ?
- I have this oil cooler, which need a long adapter for mounting, -it is a known product ?

[DresdaHonda]

The 29 mm keihin

[gschuld]

I'm not sure what the guy used for o-rings but they're on the "large" size! Most, myself included, cut a 0.08-1.0mm groove and use SS wire in the cylinder sleeve flange with a copper gasket.

Um, wow.  Never seen that before.  Huge rubber O-rings?  Interesting...

George

[gschuld]

- I have this oil cooler, which need a long adapter for mounting, -it is a known product ?

Sure, it's a classic.  It's an early Lockhart oil cooler with a Lockhart bypass.  I believe the idea for the bypass (the small can) is to bypass the cooler until the oil temp reaches a preset temperature, then allows the oil through.  The idea is to allow the engine to warm up faster, and perhaps prevent over cooling in certain conditions( like perhaps highway travel on a very cold day)

George

[MRieck]

I'm not sure what the guy used for o-rings but they're on the "large" size!

Look more like inner tube rings. Seriously....what is that about??

[SOHC4 Cafe Racer Fan]

When Mike scratches his head (on the O-RING recesses), you know it's "out there."

If you 26's and 29's are racked for a 69-76 CB750K, they should work on a 1979-1980 CB650 head.

[simon#42]

that is probably for cooper rings mike , it is a good solution to head gasket problems
was used allot in racing car engines back in the 70's . lotus and cosworth and ferrari  were all fond of them , you still see
them in high performance turbo engines .

oh they are a hollow metal ring filled with nitrogen , you might know them as wills rings

[DresdaHonda]

Well, I took a look at the CB650 engine, there is for sale at my nearby Honda garage.
On the good side
-it is an early model engine no. RC03E-2016726
-the head "ported" for 29mm cabs
on the bad side
no carburetors and the one I have don't fit (spacing in the rack)
It is bore up to 61,8 mm (or 62 mm, did not have the right tools for measure) with 4 valves pistons !!
(the ex. valves have make marks in the pistons  )
a broken fork in the gearbox
So mayby the setup is gonna be this CB650 engine with Dynoman 62 mm piston kit and a valves job

[MRieck]

that is probably for cooper rings mike , it is a good solution to head gasket problems
was used allot in racing car engines back in the 70's . lotus and cosworth and ferrari  were all fond of them , you still see
them in high performance turbo engines .

oh they are a hollow metal ring filled with nitrogen , you might know them as wills rings

I haven't run across that Simon.....sounds like a European thing. Plus I'm so young!    I have used stainless o rings...up to 2 if necessary (one in the head and one in the deck).