Topic: Cb550-cb650 swap.

[TPatocka75]

Hey everyone,

I'm looking to buy a 74 cb550 frame that I can swap my 81 cb650 motor in to. I've read a few things saying that it should be a direct swap. However the frame I'm looking to buy is just a bare frame. I was wondering if everything on my 81 660 would bolt on to the frame or not. Such things like the rear wheel, foot pegs, shifter, rear brake pedal, rear brake assembly, etc. Please let me know asap as I have a frame that I am currently looking to buy. Also if anyone knows of any pages with other step by step details, I would greatly appreciate it!

Thanks,
Travis

[SOHC4 Cafe Racer Fan]

Everything should bolt on/in.  You will need your 650 electronics.  Also, you will need to remove the oil pan, oil filter and valve covers to install the 650 engine into the 550 frame.  I am not sure if the 650 airbox will fit, but most likely.

[rb550four]

Hold on there. I just caught up with this thread. Yes the 650 engine is a direct swap into the 550 cradle. You have a bare framethere will be some foolin around coming up.
 Only entire front end including trees will swap directly to the 550 frame. the 550 and 650 PARTS in the front end are not interchangable.

650 Rear wheel does not fit in 550 swing arm. Use 650 swing arm in 550 frame....might as well use the 650 shocks too.

there will be some fitting to do with the electrical system, coil  mounts, battery box, cdi mounting, electric panel mounting....
http://forums.sohc4.net/index.php/topic,137317.25.html     Starts at entry 48 , page 2  on a 550 F frame swap. I like the F swap, it finishes nicer than a K swap.
 
seats don't swap, r fender to modify , it's been a while but most of what does and doesn't swap is in this thread. There may even be a thread on the K 500/650 swap somewhere in that thread or the thread I posted before that . anyways , lots of members have done this and if you hit Search, it should give you some direction and a better idea of what you'll be getting into.

On reply 104 , I left a reminder that the brake pedal would be from an F , even on the K frame , i think.

[SOHC4 Cafe Racer Fan]

Hold on there. I just caught up with this thread. Yes the 650 engine is a direct swap into the 550 cradle. You have a bare framethere will be some foolin around coming up.
 Only entire front end including trees will swap directly to the 550 frame. the 550 and 650 PARTS in the front end are not interchangable.

650 Rear wheel does not fit in 550 swing arm. Use 650 swing arm in 550 frame....might as well use the 650 shocks too.

there will be some fitting to do with the electrical system, coil  mounts, battery box, cdi mounting, electric panel mounting....
http://forums.sohc4.net/index.php/topic,137317.25.html     Starts at entry 48 , page 2  on a 550 F frame swap. I like the F swap, it finishes nicer than a K swap.
 
seats don't swap, r fender to modify , it's been a while but most of what does and doesn't swap is in this thread. There may even be a thread on the K 500/650 swap somewhere in that thread or the thread I posted before that . anyways , lots of members have done this and if you hit Search, it should give you some direction and a better idea of what you'll be getting into.

On reply 104 , I left a reminder that the brake pedal would be from an F , even on the K frame , i think.

Good clarification points, rb. 

I understated about compatibility.  I meant to state the entire front for either model should be used.  The individual parts are not mix and match.  The spacing between calipers and perhaps forks is different.  I did not know that the 650 wheel would not fit in a 550 swingarm.  That's a new nugget of info.

[rb550four]

  The 650 swingarm is about an inch and a half longer than the 550 , that allows the wider 650 rim and tire the proper clearance . the 550 rear sprocket and chain is not interchangeable and the chain size is different. so the easiest way to deal with this is change the entire rear too ( just like the front end) it'll all change over but is not interchangeable. If you  desire spoke wheels  the 650 , not the 650 custom would be the donor of choice, all 650 customs come with comstar wheels. If it's a dual front disc that does it for you then you are talking about the 81 custom 650 ( i think)  it's only available on comstar wheels ,not spoke wheels. the tires  on any 650 is better than could be had on any 550. I believe the 650 to be a better handling machine over the 550 so I'm always happy to make the swap ,even if it means no spokes.
  Oh  and it is easier to use the 650 wiring harness than it is to alter the 550 harness  since the fuse panel is up near the bars and the cdi boxes and all. it'll take some trail and error to fit it all in the 550 frame  using the 550 battery box , but it's not that hard.
 that is the major amount of changes that you would run into.
  Oh ,be sure to get some new handlebars because all 650 bars suck.but try to get some where the grips turn a little downward, it'll help out with the brake reservoir, they aren't meant to be on broomestick or dragbars.

[Ramrod79]

Thought I'd throw in my 2 cents here since I couldn't find the information anywhere else when I was researching.  I'm currently working on my 550/650 swap.

The 650 swingarm is ALMOST a direct fit with the 550 frame.  Only issue is with the pivot bolt.  The 650 swingarm pivot bolt is 16mm, while the 550 swingarm pivot bolt is 14mm.  That leaves you with 2 options.

1.) Drill out the 550 frame to accommodate a 16mm swingarm bolt (which I do not recommend)
2.) Replace the bearing sleeve in the 650 swingarm so the ID is 14mm.

I recommend option 2, however, it is difficult to locate a 9 inch long bearing sleeve with those exact dimensions. 

You can fit the 650 wheel into the 550 swingarm but you should definitely NOT do that... the stock 650 wheel spacers won't allow it to fit but if you find some smaller replacements it will fit.  HOWEVER, the rear wheel will not be centered with the front wheel, and no amount of adjusting the spacers (short of bending the swingarm) will allow you align the front and rear wheels.  And as you should know, you shouldn't ride a bike whose front and rear wheels are not aligned properly.

Hope this post helps!

[rb550four]

  Yes to all of that . and that's why I drill out for the 650  swing arm bolt and use the entire rear assembly....avoids all these issues and you can use the same 650 chain, and the better 650 shocks...not worry about alignment or angles because you will be at the 650 geometry. All those problems solved by the factory. Why reinvent the wheel?
  How's the project going , will there be pics?
 

[Restoration Fan]

rb,
After you drill out the 550 hole to accommodate the 650 swing arm bolt, do you do any kind of strengthening around the edge of the hole?  Like maybe welding a bead around the edge or something?

[rb550four]

   You could if you like. I don't, because there is plenty of material left and it's all welded in at the factory, doesn't mean it can't be improved.

[Darren Jakal]

Bringing this back as I am looking for a rear brake pedal to modify to work with by the rear sets I'm making for my 78 cb550k.

I have a good pedal that I want to save for the other build I have in mind that will be mostly stock.

I've come across some one with a 78 cb650 rear brake pedal and I just want to confirm that it will work with my bike.

What I have been able to find so far is that it should work.

Anyone confirm this, thanks !, dj

[rb550four]

   It's been a while since I've looked back at my thread  http://forums.sohc4.net/index.php/topic,137317.100.html  post 104  page 5  . But I seem to remember about a stock brake pedal switch that had to be done on either the f or k 500 or 550 frame for clearance while using the stock 650 exhaust pipes on the 650 engine in either of those 2 frames. The k's came with a tubular type of brake pedal that wouldn't offer enough clearance to get by the pipes in a downward position  ...it would sit under the peg but had no room to be pushed downward to engage the rear brake. So as I recall , and it's been a while, but I think I used a stock 76 F model brake pedal as it wasn't tubular in design and offered enough clearance with stock exhaust pipes to engage the rear brake in a downward position in the stock location without altering the pedal. I just took a look on the 78 650 that I picked up on page 4 and it also has a tubular type pedal which I don't believe would work in the stock location with stock exhaust as that frame is so close to the 500/550 frame and it wasn't until the  next year when the frame  design  was changed to a cruizer type frame that most of us use as the donor bike for the swap.
  I don't know what design you have come up with for the rear  sets that you are making, what they are made of or where you are going to mount and position the brake lever that you say you will need to modify.......so then, will the unmodified 78 650 brake pedal work? Hell , no one can confirm that, there's too many variables in this equation to offer an educated guess. even if you did mount it where ever you're going to mount it and had clearance  for the pedal next to the exhaust ,then there's still the brake rod issue ...will that work it the mount's new position ? Especially without pictures of what you are planning to do, it all sounds custom to me , why not get a set of rear sets that you know have worked on a 500/550 and take it from there?

[rb550four]

  Darren Jakal I sent a PM.

[Darren Jakal]

Hey rb, thanks for the reply (I don’t see a pm however).

I just need to know if the splined part of the brake pedal will fit the splines on the stock 550k brake actuator (for lack of a better word).

I’m just going to cut off the rest of the pedal and make up a smaller one and bolt it to what is left over.

Thanks for you help, dj

[rb550four]

 Darren, I just checked the splines between the 500/550 vs.80/81 650 splines are the same, the 80/81 would be about 2 1/4 ". clear from the inside to the frame at the actuator. I'll try to check with the 78 this afternoon to see what the story with that is.

[Darren Jakal]

Hey that's great rb !

Here is a photo of my ghetto set-up. It's very low tech, low budget, but I want to keep a set of original controls so I can get it on the street if things don't work out with my experiments.

You see I have a good pedal that I don't want to wreck and why I'm looking for a junker one.

This set-up is based on what I found out about the CB 400 rear sets. I still want to be able to use the kick starter and why I am using the passenger pegs as they fold up. I'm planning to eventually get some nicer folding pegs, but this is what I've got for now.

So if I can get the 650 pedal to fit my 550 splines then as long as I can cut off what I don't need with enough left over to bolt on a new portion I should be good to go.

Cheers, dj

[rb550four]

  DJ,
 I'm back. You do know that a 650 engine from the factory has no kick start right?
 My f  frame required the 76/77 brake pedal as it isn't tubular and offered enough clearance around the stock 650 2 into 1 pipes to actuate the rear brake without interference , the other pedals didn't work
  My k frame was able to work on a early 80's 650 brake pedal with stock 650 pipes no problem but hasn't much extra room.
The 79  has a Mac 4 into 1 header that lays beneath the frame further towards center of the width of the frame ,unlike the stock exhaust that is outside of the lower frame  and will accept either pedal without interference. Looks like all the same spline.
I know there has been other members that have used a 400 set up, I never have . Perhaps one of those folks could chime in and shed some light on this? I used the search and came up empty on who it really was but I think I read about it once on one of Scot S (the member with the hippy bike) threads over the years. I could be wrong but it's somewhere to start looking if no one chimes in.

[Darren Jakal]

Hey rb, I’m not doing any converting from a 650 to 550.

I just found someone local with parts and I asked him if he had any 550 brake pedals.

Hey said he only had 650 pedals.

So I’m just trying to determine if the 650 would work with what I am doing and that is making a shorter brake pedal for my 550 with cb 400 style rear sets.

And from what I have found is that the lever he has for sale is a tubular style one and therefore I don’t want it.

I want enough metal to cut some threaded holes to bolt on the shorter lever I will make. The cast one is solid all the way through and gives me more to work with. So I will now be only looking for this type.

Thanks for your help in figuring that part out !

Cheers, dj

[rb550four]

  I've been looking around the interweb for one.....like hen's teeth, found NOS one on ebay .....$220 I don't have any more of them around here. Sorry.

[Darren Jakal]

No problem and thanks for your help!

Cheers, dj