Topic: 550/650 hybrid or 650 big bore HOW TO

[Tews19]

How quick is she spdy? Can you post a video of how she sounds?

[spdygnzlz]

Will do when I finally get the registration sticker back from DMV.  Had to non-op the bike while I was rebuilding. 

[Brauner cb550]

Im sorry this is alot to take in, usually i build cars but in love with my 75 cb550 but i want more power.  the gf got an 81 cb650, i like her shorter intake and the rest looks similar.  I was wondering can i swap the jugs pistons and head completely for a big bore?  maybe use a 750 cam and jet up my 550 carbs??

[MRieck]

Im sorry this is alot to take in, usually i build cars but in love with my 75 cb550 but i want more power.  the gf got an 81 cb650, i like her shorter intake and the rest looks similar.  I was wondering can i swap the jugs pistons and head completely for a big bore?  maybe use a 750 cam and jet up my 550 carbs??

The 650 head IS much better BUT there are many nuances associated with it ESPECIALLY if you want a performance cam etc. I have spent hours figuring it out and modifying parts. I only deal with the heads....not the cylinders though i can tell you the 650 head will not work with stock 550 pistons.

[SOHC4 Cafe Racer Fan]

Im sorry this is alot to take in, usually i build cars but in love with my 75 cb550 but i want more power.  the gf got an 81 cb650, i like her shorter intake and the rest looks similar.  I was wondering can i swap the jugs pistons and head completely for a big bore?  maybe use a 750 cam and jet up my 550 carbs??

It's a ton easier to just swap a 650 motor into your frame.  If you want to extract more power, you can upgrade the head with porting (see Mike), up the compression and displacement with a 674 Dynoman kit and upgrade the cam.

[per]

Hi
I am at the moment collecting parts for a cb 500 with 650 head. Now, I read here that cb 900 liners would work. I  got myself a 900 cylinder row but that looks a bit large, as in too big to be able to fit to cb 500 cylinder block.
So, is it possible or do I need  a set of dohc or sohc 750 barrels?
 Cheers.........Per

[turboguzzi]

OP paulages seems to check in every now and then, try to PM him. Not such a common mod, dont think there are many folks with the experience to answer

[Ricky_Racer]

THIS IS A SHAMELESS PLUG.... if anyone in SoCal is looking for a CB650 motor, I've got one I'm not going to use. PM me.

RR

[RAFster122s]

The cylinder block would have to be bored to accommodate the cb900 liners. I don't know if you are going to be able to use cb900 liners in a cb550 block. Boring liners to 61.5-62mm in a cb550 block leaves them too thin to be durable long term from what I have read. With the cb900 liners are you going to have to skim the sides of the liners to get them to fit given their larger diameter or is there enough material between cylinders?

[per]

Hi
Yes thats my worry too.
Per

[RAFster122s]

It has been too long since I read Paulages' thread on the cb650/550 hybrid motor and his machinist friend died and between him and Paulage they had noodled out all the mods required to make the hybrid work. I seem to recall the need to flat side the bigger liners to make them nest together. You will have more meat on the 650 block and liners than is possible from the 550 liners, so I would start there.
The simple solution within limits is to do a high compression overbore using dynoman 650 oversized displacement pistons in a cb650 motor. While Paulage built a hybrid it was a lot of expensive machining and sorting out a lot of challenges that the high output 650 hybrid brought with it.

The 650 motor is nice but the weakness you have to overcome is the electronic ignition as the ignitors are know to be problematic...and impossible to buy new any longer. Not a monster problem as Dave Barbier I believe has machined a 550 electronic ignition pickup coil plate to fit the 650 motor allowing a commonly available proven system to replace the ignition side issues.
MReich has experience now in tackling the 650 motor valve train challenges for valves and the like. He has gobs of experience ekking out excellent power and torque out of the sohc4 powerplants so...well worth considering Mike to build you a nice flowing head and valve train to complement a dynoman high compression kit.
I would go that route rather than try to pave another path with a hybrid build using Paulages' experience and notes from this thread.

[turboguzzi]

650 is longer stroke than the 550, its block therefore taller, will not work on the 550 bottom end thats he has

of course you can do a big bore of 700cc plus from a compete 650 motor, but thats not a 550/650 hybrid anymore...

[per]

Hi, thanks for all input.
What I am trying to do is build a cb 500 bottom with 650 head and a lot of cc´s. Thats why I want to know how large liners you can fit into the cb 550/500 cylinder block. I´m sticking to wjat I have, and I dont have a 650 eninge, that wouldbe no fun at all. Its the hybrid thing I´m after. Maybe crazy or silly, but thats me.
Cheers...Per

[per]

Hi , does anybody know how big the holes are , where the cylinders gon in the crankcase. I dont remember and the Engine is in the bike at the moment. It would be helpful to see how big a liner I could fit witout having to enlarge the carnkcase mouths.
Cheers............Per

[turboguzzi]

my engine is buttoned up, but quite a bit of info on sleeving here
http://forums.sohc4.net/index.php?topic=20601.0

[tourmax]

Not trying to thread "necro", just dropping a marker so I can find it at a later date. I wish the forum had a "subscribe to thread" option.....

[RAFster122s]

There is this thing called a bookmark I use, old school solution.
Great thread, but Paulages would be beyond inundated with questions if he were to be inclined to spend a lot of time answering questions. It is going to take a skilled machinist whom is not afraid to be challenged by the work of doing this kind of work to replicate a lot of what Paulages has done. It is fascinating what he was able to achieve. Reading what Brent Waller and Mike Rieck were able to achieve on Brent's (and Tyler's,) CB550K race bike is pretty incredible as well. That solution is achievable, if you can get Mike to help rebuild your head and motor.

[gschuld]

http://forums.sohc4.net/index.php/topic,18521.0.html

This one may be a decent reference as well.

George

[Ricky_Racer]

Note: if anyone needs a CB650 motor do do this conversion, I have an '81 with all the necessary parts. It'll be cheap, so let me know. Local pickup is preferred. Thanks!

RR

[Ramrod_Racing]

Note: if anyone needs a CB650 motor do do this conversion, I have an '81 with all the necessary parts. It'll be cheap, so let me know. Local pickup is preferred. Thanks!

RR

Where are you located?

[Ricky_Racer]

San Diego

RR

[twentyover]

Ricky-Racer-

I know it's been a year and a half, but do you still have the CB650 engine? I'm moving from Orange County to the great white north , have had Mike Rieck prep a head for me.

559 engine sat outside too long and seized up, so if I'm going to rebuild something... go big ot go home

[Godffery]

Ricky-Racer-

I know it's been a year and a half, but do you still have the CB650 engine? I'm moving from Orange County to the great white north , have had Mike Rieck prep a head for me.

559 engine sat outside too long and seized up, so if I'm going to rebuild something... go big ot go home

If not, I've got a couple CB650 motors available, but I'm located in Wisconsin so not sure if that's a deal beaker for you or not?

[twentyover]

Give Rickey Racer another coupla days- if no response, I'll engage w/ Godffrey

[kayaker43]

Just throwing this out there for the guys wanting to go big on a cb500 bottom end.

The 500 had a weak clutch. The 550 fixed this by changing the primary ratio to take some load off the clutch and gearbox. The 650 did that trick again for the same reason. The concept is to spin the clutch and gearbox faster then adjust the sprockets to get the road speed you want. The 500 clutch was weak even for a 500, the 550 clutch was just enough for a modded 550 but marginal for a 650 hybrid. I wouldn't consider a big bore hybrid without the 650 clutch and primary drive. To me using the entire 650 bottom end is the best choice because you get the deep pan, primary chain oiler, better clutch and it still fits a 500/550 frame. Then dress it in cb550 engine covers and re-shape the cooling fins if you really want to disguise it. The 500/550 cam covers can work if you weld up a couple mismatched corners on the 650 head.

I scored a new old stock CB650 engine in the crate a very long time ago. Honda used to donate out of production engines to schools a lot. I missed out on the batch of new CBX engines though.