Topic: 1975 CB400F -> Project "something fun to build and ride"

[gsnorcal]

Hi,

I think this image officially marks the beginning of my project. I've been inspired by one part FunJimmy's "Interceptor" and one part "OMG these brakes are gonna kill me". So, here's what I picked up today.



That's a 99-02 Yamaha R6 front-end, with one caliper. I'll be looking to follow Jimmy's lead as far as I can on the front-end. I take night classes at the local CC machine shop, so I'll be milling and turning things down myself. I might do my own triple clamps as well, if I don't like the geometry (it will turn more slowly than the stockers due to reduced offset).

Here's the bike as I got it. As they all seem to do, it looks worse in person.



If you are wondering, the flames have been there since 1975. The previous owner has had the bike since 76 or so. It last ran 1.5 years ago. When I got it, I replaced all the ignition components and cleaned the carb. Runs now. However it has over 45,000 miles on and has really poor compression, as well as a lot of clatter. Generally running badly.

My plans:

* new front end primarily for braking enhancement (and fun machining projects)
* engine rebuild (might try that cheap Japanese 466 kit).
* some sort of resto-mod aesthetic.
* blast and powdercoat the very rusty rims (assuming they are sound)
* re-lace the wheels (new spokes)
* rear-end? who knows. Maybe a disc. Maybe a monoshock.

I'm just trying to have fun with the bike as a series of projects. I'll do all the work myself, except for boring out the cylinder. I think I try my hand at painting, too. Powder coat will go out to a shop. Welding in house. Yada yada yada.

Enough BS for now. Stay tuned.

Dave

[gsnorcal]

Can someone do me a favor and check a dimension of a CB550F front hub? I specifically am interested in the width of the hub at the flanges where the spokes attach. On the 400, the outer width of the flange is 57mm and the inner width is 50mm. This is rough, since the wheels were mounted, but I wonder if the 550 is similar or not.

Thanks!
Dave

[FunJimmy]

Dave

I know exactly what you mean about the stock brakes.
They scared the crap out of me the first time I rode my bike too.
You’re gonna like the improvements that front end will provide, I guarantee it!

Good luck with the build.

Cheers
FJ

[FunJimmy]

Can someone do me a favor and check a dimension of a CB550F front hub? I specifically am interested in the width of the hub at the flanges where the spokes attach. On the 400, the outer width of the flange is 57mm and the inner width is 50mm. This is rough, since the wheels were mounted, but I wonder if the 550 is similar or not.

Thanks!
Dave

Very similar I'm sure, but I'll go out and measure for you later tonight.

[Syscrush]

Oh, I beg you to keep that paint.

Watching with interest.

Those forks are the absolute shizzzzz - I had 'em on my old SV and they worked wonders, a huge improvement even compared to 41mm forks 25 years newer than the CB's.

[cdoggy81]

I'll be watching

[FunJimmy]

Can someone do me a favor and check a dimension of a CB550F front hub? I specifically am interested in the width of the hub at the flanges where the spokes attach. On the 400, the outer width of the flange is 57mm and the inner width is 50mm. This is rough, since the wheels were mounted, but I wonder if the 550 is similar or not.

Thanks!
Dave

Dave

My 550F hub measures 55mm between the spoke flanges and approx 67mm on the outside of them.
Wider spacing will make for a stronger wheel and help fill the gap between those forks so find a 550 or 750 hub.

[gsnorcal]

Thanks FJ.

Scratching head now... 550 is wider, stronger. But also 40 spoke and 19", so need another 18" rim too. But it would also let me keep all the 400 stock parts, which might be nice...

But the 400 might save me from some of the shaving down of the caliper... but it would also need wider disc carriers to push the rotor out where it needs to be. That might look weird...

:brainspins

I posted a "wanted" ad earlier. Hopefully I can drum one up here (or eBay).

Dave

[FunJimmy]

Or you could purchase both Triumph Thruxton alloy spoked wheels on ebay and one up all of us.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220725263964&ssPageName=STRK:MEWAX:IT

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220725275277&ssPageName=STRK:MEWAX:IT

Timing is everything!

[gsnorcal]

OK, I've sourced most of the parts I need. The following is in the mail from various sources:

* used 18x1.60 40 spoke rim
* used CB550F front wheel (hub donor)
* used CBR900RR rotor (same p/n as CBR F3)
* All Balls tapered stem bearings (their front-end conversion tool is handy)
* new R6 wheel bearings, seals, and bearing spacer (will trim to length)

I think I'll be able to use Buchanan pre-packaged CB550F to 18" spoke kit. Will need to measure the 18" rim.

Dave

[TPColgett]

I will eagerly keep an eye on if this works since I have a pair of 550F spokes sitting in the back of the garage and would really like to run dual disks on my 400F....

[gsnorcal]

I grabbed a wrench, and 3 hours later...



Given that oil was leaking from both the base gasket and head gasket, I guess I shouldn't be surprised that the head and cylinder came off as easily as they did.

Mostly looked pretty good inside, not that looks matter much. I'll commence cleaning and measuring soon. What I did notice is the piston shirts had a lot of rust staining on them. And the cam chain tensioner guides appear well worn.

I'll remove the motor as soon as I have a helper, then crack the cases.

Dave

[Syscrush]

Good work, man.

[gsnorcal]

Got a lot done today. Got this far on the teardown:



And went to HF and grabbed a 20 gal parts washer. Got a few items soaking in it now. Working pretty well so far.

Here are the pistons:



I need to clean the cases a little more by hand before I open them up. I don't want all that road gunk getting in there.

I suspect my top end wasn't getting full oil flow. When I removed the oil jets that sit between the cylinder and the head, most of the holes were plugged with little bits of crud (metal or?). In this pic you can see the crap on my finger, as well as a flake still in one of the jet holes:



My 550 wheel also arrived today. Tomorrow I plan on taking lots of notes on the lacing pattern (and pics) and then I'll remove the hub. I'm glad it arrived to quickly because my shop classes start next week, and getting started on the hub machining is my first order of business.

Now beer... yum.

Dave

[kenneyginter]

looks like its coming along. good work my friend.

[gsnorcal]

CB550F 40 spoke lacing pattern

[gsnorcal]

One small step for man...



First night in the machine shop. I milled down the caliper mounts. Took 10x longer to setup the part than to do the milling. Typical. Then I spent some time measuring things and preparing for the rest of the project. I've started engineering drawings, now I'm just filling in the measurements.

Tomorrow the hub work begins. Small steps.

Meanwhile, the frame is completely torn down--swingarm and stands removed. It's all been degreased and cleaned. I noticed that the center stand is bent and cracked. Will straighten and weld.

I've also been tearing the motor apart and cleaning all the parts. Today I soda blasted the carbon off the valve faces and the top of the combustion chamber.

Dave

[FunJimmy]

Nice work Dave.
Can't wait to see more.

Centre stand = recycling bin. 

Cheers
FJ

[Syscrush]

Centre stand = recycling bin. 

I'm glad someone else said it first.

[gsnorcal]

Centre stand = recycling bin. 

I'm glad someone else said it first.

That thought has crossed my mind. I think I read that some folk leave the mounting tabs for occasional use for service. No welding required for that duty 

[Syscrush]

That thought has crossed my mind. I think I read that some folk leave the mounting tabs for occasional use for service. No welding required for that duty 

I did that on my old Katana - you're better off just springing a few bucks for proper front & rear stands.

[gsnorcal]

Tonight I bored out the CB550 hub and faced it off:





I also got a little farther on splitting the cases, but there is something in there keeping them from coming fully apart. I can only get them about 1cm apart at the front. I'll try again tomorrow, or perhaps wait until I can get a second set of hands. Anything obvious I am missing?

Oh, and I finally managed to get the last of the stuck float drain screws out of the carb bowl. Totally buggered the screw, but all 4 bowls are OK.

In general, working on old bikes is very different from the new ones. Everything is harder to get undone, and more likely to break. And then not able to be found for replacement. I'm learning to be more careful and patient.

I broke this little rubber gizmo on the carbs today. I don't even know what it does:



Dave

[joshuanagao]

I broke this little rubber gizmo on the carbs today. I don't even know what it does:

The rubber piece is basically protection so dirt and other crap don't get into the inside of the spring housing. Think of it as a dust seal.

[RickB]

Dave,

I wish I could fabricate stuff like what you're doing. I love it.

I recently rebuilt my 400F carbs. I had no idea how they do what they do before I started. A month later of being up to my elbows in carb linkages I have a much better understanding.

That rubber piece is a gasket of sorts. It stops grime and gunk from getting into your balancing springs and hence making it difficult for your individual carbs to move in sync. I have bought several spares from the very helpful Steve at 400fourbits.co.uk but they are difficult to come by in non-brittle rubber. You may have better luck making your own out of rubber or silicone or something.

You can see how I went about my carb rebuild here:

http://forums.sohc4.net/index.php?topic=51957.250

I even had the same issue you had with a stuck float bowl drain screw. Except I broke an easy out trying to remove it and had to buy another float bowl.

Rick.

[gsnorcal]

Hi Rick,

Thanks, man, but I'm just a beginner with the machining. Check out your local college or even high school for night classes. It's fun stuff.

Re: the float drains, two of them came out with a screwdriver after some soaking. Then next one came out with heat and turning the screw head with vise grips. The last one took several heat/cool cycles and soaks to get out. Heat is good.

Thanks for the tips on the "gasketing" piece of the carb.

Dave