Topic: New Project - 1975 CB550K1

[juitz]

Hello everyone,

I'm in the early stages of a cafe racer build. Been riding bikes for about 25yrs now, and I've been wanting start a project(s) for about 10yrs but life tends to get in the way, but nowI finally have the time and space to put in a real effort.

I did quite a bit of research before starting and ended up purchasing a US Import, non-running 1975 CB550K. I chose this bike for two reasons. One I wanted a challenge and secondly, this forum gave me confidence to know that if I did get stuck I had a great source of experience to draw on.

As I don't know the history and condition of the internals of the bike, I decided to rebuild everything from the ground up (where I think it's required). I've completely stripped the bike down and am currently working on the carb and engine rebuild. The carbs that were on the bike were a disaster, and looked like someone had used them as a cement mixer. I had two potentially salvageable carb bodies and after uncessfully looking for two more replacement 022A bodies, I decided that it was cheaper (and a bit easier) to buy another complete set.

I've now stripped the replacement carbs down to give them a proper inspection and clean, but found that all the rubber items are petrified. I am currently trying to source the right o-rings and gaskets individually instead of buying a kit as I'd like to use the jets, tubes, etc that were on the carbs.

I now have hit my first snag as one item I can't find is the rubber damper that's part of the throttle link (see attached picture). These are not listed as individual items on CMSNL, but I did find a similar thread which says these are not made anymore but not really needed?

http://forums.sohc4.net/index.php?topic=152441.0

Can I get away with not having these or am I in trouble?

Thanks!

[SOHC4 Cafe Racer Fan]

Is there a specific reason you are choosing to rebuild the engine? Cosmetics? Leaks? Performance upgrades (back-cut transmission, big bore kit, heavy duty studs, ported head, cam)? Lack of compression? Seized motor? 

If not, you may be better off trying to get the existing motor to run before you feel it's necessary to do a rebuild.  Just an opinion.

[Little_Phil]

AFAIK the rubber bits are just an attempt to keep dirt/dust out of the ball joints. But the argument against that is that they are a strange shape and could have been just a couple of rubber washers if that was the case.
Just to add there is also a UK site of same format of this SOHC.

[juitz]

Is there a specific reason you are choosing to rebuild the engine? Cosmetics? Leaks? Performance upgrades (back-cut transmission, big bore kit, heavy duty studs, ported head, cam)? Lack of compression? Seized motor? 

If not, you may be better off trying to get the existing motor to run before you feel it's necessary to do a rebuild.  Just an opinion.

The engine is seized and I cant even select a gear, so definitely need to open the engine up.

If the state of the carbs are any indication, then Im afraid I have a lot of work to do.

Good to know about the UK site (now signed up) and the rubber bits!

[juitz]

This past weekend I started stripping down the forks and engine.

Forks are covered in rust in the usual place, and have not been successful in getting it off. Used some Jenolite rust remover but it just turned a black colour. I'm thinking that a new set might be in order. Have read through the forums and Franks Forks seems to be the place to get them? However, I'm in the UK so not sure how much shipping/taxes will add up to?

Engine is a problem - one of the pistons looks heavily corroded so I'm soaking in ATF/Acetone mixture as recommended. I'm going to try some other tricks such as heat / wooden block & hammer to get them moving. What are my options to cleaning up the piston wall? Is it salvageable, or machine it to bigger bore?

One further concern I have is that the shift lever is also stuck. The front sprocket turns freely, so the clutch must be disengaged? (will check this on the weekend)
Any idea what could jam the shift mech? I dont want to put too much load on the pistons when trying to free them up and inadvertently damages something else.

Thanks!

[Stev-o]

Hello from Texas...that bike project will definitely be a challenge!  Dont think I"ve seen carbs in worst shape, cant imagine what kind of fuel was left sitting in them?!
Highly doubt honing will clean up that cylinder wall so boring would be one option. Personally, I would seek out a nice replacement, may be cheaper than boring?  [last rebuild I did, boring was $50/hole]  But I realize you are in the UK and parts may not be as available as in the US  [I bought a spare 550 motor from a buddy that was moving for $20]

Good luck

[juitz]

Hello from Texas...that bike project will definitely be a challenge!  Dont think I"ve seen carbs in worst shape, cant imagine what kind of fuel was left sitting in them?!
Highly doubt honing will clean up that cylinder wall so boring would be one option. Personally, I would seek out a nice replacement, may be cheaper than boring?  [last rebuild I did, boring was $50/hole]  But I realize you are in the UK and parts may not be as available as in the US  [I bought a spare 550 motor from a buddy that was moving for $20]

Good luck

Hi Stev-o, you're right that parts are not as available here, just had a quick look and there's not much.

There's a couple of cylinder blocks on ebay incl. pistons (although with fin damage) at not an eye watering price. I was expecting at worst case on replacing the pistons anyway as part of the rebuild.

I wonder if resleeving the single cylinder is an option?

[stokey]

 try this place they have a huge warehouse full of stuff, they do sell on ebay but dont put it all on there
 I have had a few bikes & parts from them, but they are local to me I live in Stoke on trent.  got to be worth a call they can only say no Alan
 https://www.bing.com/search?q=dk+motorcycles+uk+used+spares&cvid=5f3f904daf8e4146b0e2ffeb51d6a809&aqs=edge.2.0l7j69i60l2.7884j0j1&pglt=43&FORM=ANNTA1&PC=HCTS#

[juitz]

Thanks stokey! I'll definitely give them a call.

I had 30mins free last night and took the clutch cover off and removed the clutch basket. I need to get familiar with the shaft layout but there are 3 visible shafts - kickstart and shaft that clutch basket is on rotate freely. Shaft with small pinion gear is stuck so I assume it's connected to the crankshaft/seized pistons(s)?

Rotaring the front sprocket by hand turns the clutch carrying shaft via drag so assume this is normal?

[rb550four]

 Nice project you have there, it's gonna take some workto bring it back though. Looks like a bore job is in your future and it sounds like the shifting forks are frozen. Looks like you'll be splitting the cases. and just as well, as every piece  inside that transmission will be needing a clean up. Pay particular attention to wear marks from a worn cam chain ,look up from the bottom around it's path, I always replace them anyways ,some don't and find it to be a problem they could fixed before it went back together....same holds true with the primary chain they stretch and feel sloppy. The shift dogs are located inside the  top of the transmission  roof ...they sound seized as they get no oil bath in an upright position during long periods of storage and are effected by condensation they do come out and clean up well with some effort but don't put seriously warn or damaged ones back in.check the condition of the bearings,use engine building lube as you go,new seals all around,  check the kickstart action before you start to assemble the top end  , by that time you should be getting those cylinders back from the machinist..Take a good look at the valves and seats , and check the valve guide condition and the seats especially close in that rusted cylinder before you go to the machinist in case they need a little clean up or more. And an air compressor is the best way to clean engine internals, hope you have that and a manual . It all fun and even more fun when it's challenging. Looking forward to your progress.

[juitz]

Nice project you have there, it's gonna take some workto bring it back though. Looks like a bore job is in your future and it sounds like the shifting forks are frozen. Looks like you'll be splitting the cases. and just as well, as every piece  inside that transmission will be needing a clean up. Pay particular attention to wear marks from a worn cam chain ,look up from the bottom around it's path, I always replace them anyways ,some don't and find it to be a problem they could fixed before it went back together....same holds true with the primary chain they stretch and feel sloppy. The shift dogs are located inside the  top of the transmission  roof ...they sound seized as they get no oil bath in an upright position during long periods of storage and are effected by condensation they do come out and clean up well with some effort but don't put seriously warn or damaged ones back in.check the condition of the bearings,use engine building lube as you go,new seals all around,  check the kickstart action before you start to assemble the top end  , by that time you should be getting those cylinders back from the machinist..Take a good look at the valves and seats , and check the valve guide condition and the seats especially close in that rusted cylinder before you go to the machinist in case they need a little clean up or more. And an air compressor is the best way to clean engine internals, hope you have that and a manual . It all fun and even more fun when it's challenging. Looking forward to your progress.

Thanks mate, I managed to unfreeze the pistons. Getting some tips and tricks from this site (i.e. ATF/acetone mix soak, heat and big hammer). I did cut the cam chain though.

I wanted to get some advice on the pistons and of they're still usable?

I cleaned one up in an ultrasonic cleaner then ran a bit of scotchbrite to clean up the surface. Bit of pitting and a small gouge. Are these ok to use with a bit of a cleanup?

Next task - get into the gearbox!

[juitz]

Also, probably gonna be a "duh" moment but I can't get the front sprocket cover off? Taken off the 4 screws and thing is not budging? Can't see any circlips on the gear select shaft, only an ioil seal?

I'm trying to push the gear shift shaft through, but not moving at all as I'm stripping the bottom end.

[flatlander]

what's the plan for the cylinders? if you're going to  bore them out then you will need oversize pistons anyway.

the sprocket cover is probably just a bit stuck. may need a little tapping with a wooden mallet.

[juitz]

what's the plan for the cylinders? if you're going to  bore them out then you will need oversize pistons anyway.

the sprocket cover is probably just a bit stuck. may need a little tapping with a wooden mallet.

Well, I took a dead blow hammer to the case and a bit of it snapped off
After massaging the shift select shaft and using penetrating oil it came unstuck - looks like it was rusted/seized to the case which is why I couldnt select a gear originally. Anyway, it's free now so on with the show.

Not sure what I'm doing with the cylinders, have contacted a local engine shop to get options. I guess they can machine back to spec (unlikely), std pistons with oversize rings or rebore to larger pistons?

What I also need to start thinking about is what to do about the casings.Original paint is gone, so not sure if I should restore the paintwork or powercoat?

[Little_Phil]

Take it easy the jap metal is easy to damage. Give things time to soak and use heat to dismantle.
Bike will need at least a 0.25mm overbore and new pistons I suspect. Oversize rings will not work
You will need to remove the generator. That also can be stuck as it has a couple of dowels. Then the generator rotor from the end of the crankshaft. It needs a 16mm x 1.5 bolt or the like screwed into it to remove. (Should really have the end machine to locate correctly) or there is a special tool. I stuck a couple of the piston pins back in the small ends and a rod through to stop the c/s turning to get bolt in tight. Then a whack with a hammer on the end of the bolt and the rotor should pop off. (it's on a taper)

[juitz]

So it's been a few weeks since I posted but have made some progress.

Engine and gearbox is now almost completely dismantled, just have one bearing to remove. I've also purchased a blast cabinet as I intend to clean up the housings along with the carb bodies (and any other bits I can) using soda. I'm just waiting to get the compressor next week.

I've also battled with the front axle nut, and just can't get it off. I've given it a good go with heat, broken a long screwdriver. I'm now looks ng for a long socket to see if my impact driver can help.

Also been looking at the tank. Still not sure on colour scheme but I've not been successful at getting the paint off. Most of it was faded anyway but the can't get the black paint off. I've tried Nitro Mors but wondering if there's something else I should be using. I've seen aircraft remover mentioned in other threads but not sure which brand is good in the UK.
I did have a bit of a go with the grinder and a 120 grit disc but would rather avoid this if possible. Theres a good bit of oxidisation that I'll need to adress also.

I'm now planning to send my forks out for rechrome (if possible) and get new rims and wheels relaced (after I get the hubs apart!)

[HondaMan]

I'd suggest contacting CruisinImage on eBay. He also has an independent store. His CB550 pistons are good: I have used them in many 750, 500/550, 350F and 400F rebuilds.
One thing that you MUST remember, and FORCE your machine shop to do with these pistons (or any cast pistons) in this engine: the piston-to-bore clearance MUST be in the range of 0.0004"-0.0008", NO MORE. If the machine shop argues, find another shop. If the piston clearance exceeds 0.0012" then the engine will burn and leak oil, and lots of it, from the startup on. These MUST be TIGHT but most machine shops' standards. Car engines (watercooled) often have twice this much clearance, so that is what most macine shops know. These are very different.

[juitz]

Thanks for the advice HondaMan. I have seen cruisinimage store and it's always better to have recommended parts.

I've gotten a bit further on the build with a few smaller bits. Rebuilt the carbs after a good clean with a soda blaster. I also stripped the wheels to get the hubs and have the rebuilt with new rims and laces. Still not sure on wheel size though but will probably go 18" front and rear.

Also go the first coat of paint on the tank, but I can see where I filled a dent with body filler. Thought it was smooth but with paint and right light I can see the imperfections - and now I can't unsee it.

Also painted the fork tubes but the colour isnt right. I chose a metallic black for the tank and thought to paint the forks the same colour but I don't like it. Will paint over with a solid black

[HondaMan]

Thanks for the advice HondaMan. I have seen cruisinimage store and it's always better to have recommended parts.

I've gotten a bit further on the build with a few smaller bits. Rebuilt the carbs after a good clean with a soda blaster. I also stripped the wheels to get the hubs and have the rebuilt with new rims and laces. Still not sure on wheel size though but will probably go 18" front and rear.

Also go the first coat of paint on the tank, but I can see where I filled a dent with body filler. Thought it was smooth but with paint and right light I can see the imperfections - and now I can't unsee it.

Also painted the fork tubes but the colour isnt right. I chose a metallic black for the tank and thought to paint the forks the same colour but I don't like it. Will paint over with a solid black

Personally, I think painting is the hardest part of these projects. I never like my paint jobs, even when they came out fine!

[MauiK3]

Agreed, painting is tough.
I polish forks and I'm still not sure I like how they come out.