Topic: CB550 with a CB650 engine: research for future project

[grcamna2]

I will be getting a CB550 in the near future and want to do the CB650 engine swap..Need a bit more power 
This will be a project,first one here on the forum.I can choose the model/year CB550 and also want to know which model/year engine CB650 is the best one to use. what are your thoughts on it ?  thanks,Bill

I will consider buying one that's already been fixed-up that way also:or a CB550 without a motor.The CB550F is what I prefer in chassis.
Could be,the 1979' CB650 would be similar in geometry(I imagine it carries it's weight higher plus longer wheelbase?) and weight to the CB550F ??

[onepieceatatime]

The '79 and '80 CB650 use PD carbs, the '81 and '82 use CV carbs. The engine heads were changed to accommodate the different spacing of the carbs, but otherwise I believe they are all the same. The '81 CV carbs have pressed in pilot jets, while the '82 I think were removable.

[grcamna2]

The '79 and '80 CB650 use PD carbs, the '81 and '82 use CV carbs. The engine heads were changed to accommodate the different spacing of the carbs, but otherwise I believe they are all the same. The '81 CV carbs have pressed in pilot jets, while the '82 I think were removable.

What benefits are there to different model years with the heads:wider spaced later ones better ?

[onepieceatatime]

The '79 and '80 CB650 use PD carbs, the '81 and '82 use CV carbs. The engine heads were changed to accommodate the different spacing of the carbs, but otherwise I believe they are all the same. The '81 CV carbs have pressed in pilot jets, while the '82 I think were removable.

What benefits are there to different model years with the heads:wider spaced later ones better ?

I think it is more of just what you prefer, vacuum slide carbs or the earlier ones more like the 550 had, I don't believe there was a real performance difference. a few years ago, the CV carb kits were easier to find than the PD kits. Either way you go, the carbs really only like to have a factory airbox feeding them. I have seen a few cases where people got them to run without it, but after a bunch of frustration.
Another thing to keep in mind is that the 650 engine is very cold blooded. They like to run a long time with the choke on to warm up.
I have a spare engine and carbs that came off an '81 but if I needed to use it, I would swap the head and keep using my PD carbs.

[grcamna2]

I was reading one thread where the OP wanted to install round-top CB750 carbs to his later wide-spaced CB650 cylinder head.Did you read about that ? Then DaveBarbier installed aftermarket carbs to his,wonder if that improved how it was so cold blooded? I worked on a man's CB650C with PD carbs and installed a 4 into 1 exhaust,wow:that bike was VERY cold blooded after that,the customer was mad 

[grcamna2]

The '79 and '80 CB650 use PD carbs, the '81 and '82 use CV carbs. The engine heads were changed to accommodate the different spacing of the carbs, but otherwise I believe they are all the same. The '81 CV carbs have pressed in pilot jets, while the '82 I think were removable.

What benefits are there to different model years with the heads:wider spaced later ones better ?

I think it is more of just what you prefer, vacuum slide carbs or the earlier ones more like the 550 had, I don't believe there was a real performance difference. a few years ago, the CV carb kits were easier to find than the PD kits. Either way you go, the carbs really only like to have a factory airbox feeding them. I have seen a few cases where people got them to run without it, but after a bunch of frustration.
Another thing to keep in mind is that the 650 engine is very cold blooded. They like to run a long time with the choke on to warm up.
I have a spare engine and carbs that came off an '81 but if I needed to use it, I would swap the head and keep using my PD carbs.

I'd like to install round-tops

[onepieceatatime]

I remember reading a couple threads about it over the years, but do not remember ever seeing anything about the results.
I think I read about someone trying to convert to fuel injected at one point.
The other thing I forgot to mention about the PD carbs, is that the piece where the choke cable attaches is plastic, and prone to breaking. I have replaced one, and recall a thread somewhere about the metal one from the 750 carbs being compatible.
http://forums.sohc4.net/index.php?topic=146949.0

I have a set of round tops, and both style heads, I can compare and take measurements this weekend, if you want me to.

[grcamna2]

I remember reading a couple threads about it over the years, but do not remember ever seeing anything about the results.
I think I read about someone trying to convert to fuel injected at one point.
The other thing I forgot to mention about the PD carbs, is that the piece where the choke cable attaches is plastic, and prone to breaking. I have replaced one, and recall a thread somewhere about the metal one from the 750 carbs being compatible.
http://forums.sohc4.net/index.php?topic=146949.0

I have a set of round tops, and both style heads, I can compare and take measurements this weekend, if you want me to.

yes,I would like to know if the spacing will allow the use of round-tops;I don't like the PD carbs used on them.
I believe the member here needed to use a certain set of intake rubber manifold boots..

[onepieceatatime]

Here is some related reading for you:
http://www.hondacb650.com/viewtopic.php?f=4&t=722

[grcamna2]

Here is some related reading for you:
http://www.hondacb650.com/viewtopic.php?f=4&t=722

I noticed you have 2) 1980' CB650's: a standard and a CB650C.What are the styling differences:different tanks ?
I've looked online at non-USA import models of CB650 and they have different tanks on them.

[onepieceatatime]

The '79 had a different frame and tank shape, more like the F model 550/750.
The big differences in the custom and the standard models were the paint colors, the custom had chrome headlight bucket, 4 into 4 pipes, 40 tooth rear sprocket, and comstar wheels, while the standard has black plastic headlight bucket, 4 into 2 pipes, 39 tooth rear sprocket, and spoke wheels. The forks were 2 inches taller on the custom as well.
'81 switched the custom to air forks, and dual disc front brakes.
'82 got rid of the custom and introduced the nighthawk.  If you want a blacked out engine for your project, the nighthawk engine is.
the outer valve covers were cosmetically different on the '79, but will fit any of the other years.

I actually have '81 custom colors on my '80 custom, just because I liked them better than the '80 options.

[grcamna2]

The '79 had a different frame and tank shape, more like the F model 550/750.
The big differences in the custom and the standard models were the paint colors, the custom had chrome headlight bucket, 4 into 4 pipes, 40 tooth rear sprocket, and comstar wheels, while the standard has black plastic headlight bucket, 4 into 2 pipes, 39 tooth rear sprocket, and spoke wheels. The forks were 2 inches taller on the custom as well.
'81 switched the custom to air forks, and dual disc front brakes.
'82 got rid of the custom and introduced the nighthawk.  If you want a blacked out engine for your project, the nighthawk engine is.
the outer valve covers were cosmetically different on the '79, but will fit any of the other years.

I actually have '81 custom colors on my '80 custom, just because I liked them better than the '80 options.

Was the 79' CB650 much heavier than the CB550F ?

[onepieceatatime]

Was the 79' CB650 much heavier than the CB550F ?

That I have no idea, and I have never seen a '79  in person, and the last time I saw a 550, I was about 6 years old.

Here are my 650C


and 650 (carbs out for rebuild)

[DaveBarbier]

Man, a lot of 650 swaps coming up!

Benefits of the earlier years (79/80) is that early 750 carbs fit the head spacing. That really only matters if you don’t have carbs or they’re not in good shape. I believe the early 750 carbs are easier to come by. I also have heard that CV carbs are not easy to tune with pods.

The later years were styled like more of a cruiser. The frame on those are more swooping, if that makes sense. The early years were really just an upgrade to the 550. So they were styled similarly.

There are internal differences in the later years vs earlier years of the 650 but only in gear ratios. Primary reduction, all gears and final drive were different. The later years were slightly geared for highway “cruiser” type gearing where the earlier years were similar to the 550. That doesn’t really matter though. Minor differences. Plus, you can drastically change the way the bike feels by changing out sprockets.

I do not have the original air box, the 650 air box won’t fit in the 550 anyway even if you wanted to use it. I have CR26 Special carbs and they’ve been dyno tuned. Runs fantastically.

Another possible issue is that the petcock on the 550 (at least on my ‘78 550k tank) hit the CR carbs. I had to move the petcock rearward about 3-4 inches. The valve cover on the 650 is shaped differently so it comes close to the petcock. It depends what carbs you have whether or not it will be a problem. You can see in the picture where the petcock used to be, circled in red. You can see how close it is to the motor.



Oh, and lastly the exhaust for the 650 probably won’t fit on the 550 frame. I haven’t confirmed this because the exhaust for my 650 donor had to be trashed. I got the Hindle exhaust from Ripple Rock Racers. This would be nice for someone to confirm! And no, the 550 exhaust can’t be used on the 650.

So all in all it’s not exactly a direct swap. But with some minor effort it will fit and it’s an amazing upgrade. Check out my build thread for more info. There’s a table of contents on the first page which makes it easier to find things.

[DaveBarbier]

The '79 had a different frame and tank shape, more like the F model 550/750.
The big differences in the custom and the standard models were the paint colors, the custom had chrome headlight bucket, 4 into 4 pipes, 40 tooth rear sprocket, and comstar wheels, while the standard has black plastic headlight bucket, 4 into 2 pipes, 39 tooth rear sprocket, and spoke wheels. The forks were 2 inches taller on the custom as well.
'81 switched the custom to air forks, and dual disc front brakes.
'82 got rid of the custom and introduced the nighthawk.  If you want a blacked out engine for your project, the nighthawk engine is.
the outer valve covers were cosmetically different on the '79, but will fit any of the other years.

I actually have '81 custom colors on my '80 custom, just because I liked them better than the '80 options.

Was the 79' CB650 much heavier than the CB550F ?

Engine or entire bike? I weight both my 550 and 650 motors when I had them both on the bench and they weigh the same. I don’t know about the full bike. But here’s a picture from my manual.

[grcamna2]

Hello Dave, That manual,does that relate to the 1979' model ?

[DaveBarbier]

Hello Dave, That manual,does that relate to the 1979' model ?

Yup, this is the factory service manual.

[grcamna2]

The numbers look good  on the 79' CB650;why should I swap a 650 into a 550 when the 79' 650 is good. 
Did you ever own a 79' ? How does it handle compared to the 550 ?

[Scott S]

 I'll weigh in. I'll have to dig through the old hard drive for pics.

 I put a 650 in a '71 500 frame. I had the CV carbs and the petcock cleared. So did a CB650 4-1 exhaust.
 I ran K&N dual pod filters. If I remember correctly, I upped the main jets....don't remember to what... and filed the ears on the mixture screws so I could adjust them further.
 The filters slightly fouled the side covers. I zip tied them at first but eventually just trimmed them.

 I also did some math and changed the rear sprocket to match the final drive of the 650 transmission and give me the stock gearing.

[DaveBarbier]

I'll weigh in. I'll have to dig through the old hard drive for pics.

 I put a 650 in a '71 500 frame. I had the CV carbs and the peacock cleared. So did a CB650 4-1 exhaust.
 I ran K&N dual pod filters. If I remember correctly, I upped the main jets....don't remember to what... and filed the ears on the mixture screws so I could adjust them further.
 The filters slightly fouled the side covers. I zip tied them at first but eventually just trimmed them.

 I also did some math and changed the rear sprocket to match the final drive of the 650 transmission and give me the stock gearing.

Cool, thanks for the info Scott

[DaveBarbier]

The numbers look good  on the 79' CB650;why should I swap a 650 into a 550 when the 79' 650 is good. 
Did you ever own a 79' ? How does it handle compared to the 550 ?

I found in the 550 manual that it’s dry weight is 400lbs. So that’s 30lbs lighter than the 650. So it’s lighter but the difference could easily be made up with a fat rider.

The later cruiser type 650’s are not as easy to turn into a traditional cafe style bike (if that’s what one is doing) so the swap makes sense. If you have an earlier year 650 that runs and rides well then I don’t see a reason to find a 550 to swap the motor into. BUT if you have a 550 that you’re looking to upgrade and come across a 650 parts bike then it’s a no brainer. What I had was a well running 550 and found a 650 for a few hundred bucks. Did the dynoman 674cc big bore kit, megacycle 126-20 cam, MRieck’s stage 2+ porting and CR carbs over a year or two while I was having fun with the 550. Swapped it over a winter and had a 30+ hp increase. It feels good.

[onepieceatatime]

yes,I would like to know if the spacing will allow the use of round-tops;I don't like the PD carbs used on them.
I believe the member here needed to use a certain set of intake rubber manifold boots..

As DaveBarbier mentioned, the round top carbs will fit the '79 or '80 heads, much more easily than the '81 and '82 heads anyways.
I did all of these measurements from outside edges of the heads and carbs.
For the '81 and '82:
outside ports to inside port distance (1 to 2 and 4 to 3) 28mm
port 2 to port 3: 54mm
outside diameter of ports: 38mm
 
For the '79 and '80:
outside ports to inside port distance (1 to 2 and 4 to 3) 38mm
port 2 to port 3: 44mm
outside diameter of ports: 38mm

For the round top carbs:
outside ports to inside port distance (1 to 2 and 4 to 3) 35mm
port 2 to port 3: 40mm
outside diameter of ports: 40mm

Looks like you are leaning more towards finding a '79 cb650 now though.

[grcamna2]

Yes, I appreciate those numbers 'opaat'(onepieceatatime)  Thanks Man.  The 79' CB650 is a lot more like the CB550 and the parts are a closer fit.I want to set one up with round top carbs. When all these parts and pieces do get to me and sitting in front of me,I will begin my assembly.I will need to figure-out what rubber intake manifolds to use on this;I think/hope the airbox rubber boots will connect-up,depending whether I get a CB550-650 eng swap or a 1979 CB650 motorcycle.

[grcamna2]

The numbers look good  on the 79' CB650;why should I swap a 650 into a 550 when the 79' 650 is good. 
Did you ever own a 79' ? How does it handle compared to the 550 ?

I found in the 550 manual that it’s dry weight is 400lbs. So that’s 30lbs lighter than the 650. So it’s lighter but the difference could easily be made up with a fat rider.

The later cruiser type 650’s are not as easy to turn into a traditional cafe style bike (if that’s what one is doing) so the swap makes sense. If you have an earlier year 650 that runs and rides well then I don’t see a reason to find a 550 to swap the motor into. BUT if you have a 550 that you’re looking to upgrade and come across a 650 parts bike then it’s a no brainer. What I had was a well running 550 and found a 650 for a few hundred bucks. Did the dynoman 674cc big bore kit, megacycle 126-20 cam, MRieck’s stage 2+ porting and CR carbs over a year or two while I was having fun with the 550. Swapped it over a winter and had a 30+ hp increase. It feels good.

Dave,I remember your build  thread and was watching it come together while you built the Patina Hyena.I also liked when you chose to pump-up the engine and wanted to ask,now that you've had a couple years to enjoy the finished product: How do you like the bike and have you been able to keep-up with any other bikes that surprised you? are you glad you did the swap rather than just getting a CB650 ? Can you tell the difference in handling between an early CB650 and the CB550 ?  Thanks,Bill

[DaveBarbier]

The numbers look good  on the 79' CB650;why should I swap a 650 into a 550 when the 79' 650 is good. 
Did you ever own a 79' ? How does it handle compared to the 550 ?

I found in the 550 manual that it’s dry weight is 400lbs. So that’s 30lbs lighter than the 650. So it’s lighter but the difference could easily be made up with a fat rider.

The later cruiser type 650’s are not as easy to turn into a traditional cafe style bike (if that’s what one is doing) so the swap makes sense. If you have an earlier year 650 that runs and rides well then I don’t see a reason to find a 550 to swap the motor into. BUT if you have a 550 that you’re looking to upgrade and come across a 650 parts bike then it’s a no brainer. What I had was a well running 550 and found a 650 for a few hundred bucks. Did the dynoman 674cc big bore kit, megacycle 126-20 cam, MRieck’s stage 2+ porting and CR carbs over a year or two while I was having fun with the 550. Swapped it over a winter and had a 30+ hp increase. It feels good.

Dave,I remember your build  thread and was watching it come together while you built the Patina Hyena.I also liked when you chose to pump-up the engine and wanted to ask,now that you've had a couple years to enjoy the finished product: How do you like the bike and have you been able to keep-up with any other bikes that surprised you? are you glad you did the swap rather than just getting a CB650 ? Can you tell the difference in handling between an early CB650 and the CB550 ?  Thanks,Bill

I love the bike. It still makes me smile when I really give it the beans. As James May would say, it gives me the fizz. I don’t really ride with a lot of other people but I was on a ride with guys with new bikes (not crotch rockets) and I’m right there with them. They were definitely surprised. Getting a 650 wasn’t even a thought, I wanted to do a swap and that’s what I did because I like the aesthetics of my bike. I have never ridden a 650 so I can’t speak to the handling. I imagine the later years didn’t handle as well as the earlier years since they were pretty much a 550 that hit the gym vs a cruise type. Are you veering towards just getting a 650 or still contemplating a swap?

[onepieceatatime]

Yes, I appreciate those numbers 'opaat'(onepieceatatime)  Thanks Man.  The 79' CB650 is a lot more like the CB550 and the parts are a closer fit.I want to set one up with round top carbs. When all these parts and pieces do get to me and sitting in front of me,I will begin my assembly.I will need to figure-out what rubber intake manifolds to use on this;I think/hope the airbox rubber boots will connect-up,depending whether I get a CB550-650 eng swap or a 1979 CB650 motorcycle.

I can measure the rubber boots and intake side of the carbs too if you would like. I'll be back at the garage tomorrow.

Sent from my Pixel 4 XL using Tapatalk

[Scott S]

 About halfway down page 4, I start covering the 650 swap. Hurry now and you can see the pics, before Photobucket limits the monthly bandwidth!

http://forums.sohc4.net/index.php/topic,67907.75.html

[grcamna2]

Yes, I appreciate those numbers 'opaat'(onepieceatatime)  Thanks Man.  The 79' CB650 is a lot more like the CB550 and the parts are a closer fit.I want to set one up with round top carbs. When all these parts and pieces do get to me and sitting in front of me,I will begin my assembly.I will need to figure-out what rubber intake manifolds to use on this;I think/hope the airbox rubber boots will connect-up,depending whether I get a CB550-650 eng swap or a 1979 CB650 motorcycle.

I can measure the rubber boots and intake side of the carbs too if you would like. I'll be back at the garage tomorrow.

Sent from my Pixel 4 XL using Tapatalk

Opaat,
Do you have CB650 rubber manifolds for the early head ?

[grcamna2]

About halfway down page 4, I start covering the 650 swap. Hurry now and you can see the pics, before Photobucket limits the monthly bandwidth!

http://forums.sohc4.net/index.php/topic,67907.75.html

Scott S,
I looked(decent pics about to expire,thanks and learned what you and your Father did for the swap.
How did you work out the clearance for the bottom of that header ?

[grcamna2]

The numbers look good  on the 79' CB650;why should I swap a 650 into a 550 when the 79' 650 is good. 
Did you ever own a 79' ? How does it handle compared to the 550 ?

I found in the 550 manual that it’s dry weight is 400lbs. So that’s 30lbs lighter than the 650. So it’s lighter but the difference could easily be made up with a fat rider.

The later cruiser type 650’s are not as easy to turn into a traditional cafe style bike (if that’s what one is doing) so the swap makes sense. If you have an earlier year 650 that runs and rides well then I don’t see a reason to find a 550 to swap the motor into. BUT if you have a 550 that you’re looking to upgrade and come across a 650 parts bike then it’s a no brainer. What I had was a well running 550 and found a 650 for a few hundred bucks. Did the dynoman 674cc big bore kit, megacycle 126-20 cam, MRieck’s stage 2+ porting and CR carbs over a year or two while I was having fun with the 550. Swapped it over a winter and had a 30+ hp increase. It feels good.

Dave,I remember your build  thread and was watching it come together while you built the Patina Hyena.I also liked when you chose to pump-up the engine and wanted to ask,now that you've had a couple years to enjoy the finished product: How do you like the bike and have you been able to keep-up with any other bikes that surprised you? are you glad you did the swap rather than just getting a CB650 ? Can you tell the difference in handling between an early CB650 and the CB550 ?  Thanks,Bill

I love the bike. It still makes me smile when I really give it the beans. As James May would say, it gives me the fizz. I don’t really ride with a lot of other people but I was on a ride with guys with new bikes (not crotch rockets) and I’m right there with them. They were definitely surprised. Getting a 650 wasn’t even a thought, I wanted to do a swap and that’s what I did because I like the aesthetics of my bike. I have never ridden a 650 so I can’t speak to the handling. I imagine the later years didn’t handle as well as the earlier years since they were pretty much a 550 that hit the gym vs a cruise type. Are you veering towards just getting a 650 or still contemplating a swap?

Dave,I hope to see how a fellow member here likes the handling of their 79' CB650.The bike has an inch longer wheelbase than the CB550,was wondering how the rake and trail are different than the 550.

[onepieceatatime]

Yes, I appreciate those numbers 'opaat'(onepieceatatime)  Thanks Man.  The 79' CB650 is a lot more like the CB550 and the parts are a closer fit.I want to set one up with round top carbs. When all these parts and pieces do get to me and sitting in front of me,I will begin my assembly.I will need to figure-out what rubber intake manifolds to use on this;I think/hope the airbox rubber boots will connect-up,depending whether I get a CB550-650 eng swap or a 1979 CB650 motorcycle.

I can measure the rubber boots and intake side of the carbs too if you would like. I'll be back at the garage tomorrow.

Sent from my Pixel 4 XL using Tapatalk

Opaat,
Do you have CB650 rubber manifolds for the early head ?

I have '80 and '81 parts. The '80 engine, carbs, and mount rubbers are the same as the '79. I don't know if the air box and those rubbers are the same though.
I have both models from '80, a complete '81 custom with no title, and 2 incomplete standard model parts bikes, one '80 (engine was blown) and one '81, plus a spare '80 engine.

Sent from my Pixel 4 XL using Tapatalk

[grcamna2]

The 80' have the same airbox as the 79'? Would you see if a pair of round-top CB750 carbs will fit into that if you have the parts ? Thanks 

[Scott S]

About halfway down page 4, I start covering the 650 swap. Hurry now and you can see the pics, before Photobucket limits the monthly bandwidth!

http://forums.sohc4.net/index.php/topic,67907.75.html

Scott S,
I looked(decent pics about to expire,thanks and learned what you and your Father did for the swap.
How did you work out the clearance for the bottom of that header ?

 Honestly, I don't remember. I think I just moved it around as we tightened it up and it cleared.

[onepieceatatime]

The 80' have the same airbox as the 79'? Would you see if a pair of round-top CB750 carbs will fit into that if you have the parts ? Thanks 

I looked up part numbers, '79 and '80 have different part numbers for the airbox and airbox rubbers.

[grcamna2]

The 80' have the same airbox as the 79'? Would you see if a pair of round-top CB750 carbs will fit into that if you have the parts ? Thanks 

I looked up part numbers, '79 and '80 have different part numbers for the airbox and airbox rubbers.

Oh,
Do you think the round-tops might fit the 1980' airbox rubber flanges ?

[onepieceatatime]

Oh,
Do you think the round-tops might fit the 1980' airbox rubber flanges ?

They will fit, but the rubbers are loose, so I don't know how well they will seal even with smaller clamps.


CB650 carbs


Round top carbs

[grcamna2]

Thanks for that 'Opaat',I appreciate you measuring.I'll figure out a way to add custom flange parts if it comes to that. 

[onepieceatatime]

No problem!!