Honda CB-1 spiff up

GB500guy

Well-known member
After a bit of mechanical work and cosmetic upgrades the bike is just about where I want it. The main initial problem was a dud rear shock with zero dampening in half of its travel. The stock shock is known to be too flabby anyway, and various styles of CBR shocks can be fitted with minor changes. I found a low miles CBR1100XX Blackbird shock on ebay to transplant. It is 4 mm longer which would have raised the rear about 3/4" higher. Being inseam challenged I decided to make a new bushing for the top end with the bolt hole offset to approximate stock shock length. After turning a piece of Delrin to the correct OD I used a 4 jaw chuck to offset the piece 3 mm for drilling the hole for the steel collar.

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A socket set screw threaded through the shock and into the Delrin keeps the bushing from turning in the shock eye.

And viola, the shock bolts right in. From this camera angle the shock appears to touch the frame but there is actually adequate clearance.

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Even though made for a heavier bike, springing for this shock is a good match because of the difference in mounting geometry. And unlike the original, this shock has adjustable damping plus about 1/3 more travel.

There was some corrosion and peeling paint on the leading edges of the forks and clutch cover and a few rust spots and scratches on the swing arm, so I stripped off the old paint, glass bead blasted, and repainted.

Before:

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Stripping and blasting - I like how bead blasting leaves a perfect fine texture for good paint adhesion:

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It was fun to get my first peek inside the engine.

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Dupli-Color BFM0225 Medium Charcoal Metallic turned out to be a perfect match to the original color. I followed up with two coats of SprayMax 2K gloss clear coat for fuel resistance and toughness. This catalyzed clear leaves a much higher gloss than the original paint, but I like a little tasteful bling. I buffed all fasteners and clear coated most of them as well. The after:

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I went ahead and replaced the chain and rear sprocket as well.

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I like shiny clean hardware because.....bling!

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I have Oxford heated grips on two other bikes and really like them, so......

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The front dampening felt too stiff, so while I had the forks apart I used a viscosity cup to measure the current oil. It took 34 seconds to empty which is quite high compared to typical fork oils. I changed to synthetic ATF which measured 21 seconds. The front feels much more compliant now while still having good dampening.

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Stock gearing is really low, like 7,300 rpm @ 65 mph low. Perfect for the drag strip but way buzzier than needed for normal riding. So I dropped 4 teeth on the rear sprocket which feels much more normal. But in the "what were they thinking?" department, Honda chose to drive the speedometer off the countershaft, so gearing changes affect speedometer and odometer readings. But it turns out that in sixth gear the tachometer reading is very close to mph, i.e. 6K rpm is 60 mph. The speedo drive cable:

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So for now the bike is basically where I want it except for one dent in the tank. It's not bad enough to warrant repainting so I might check with paintless dent repair shops and see if anything can be done. Unfortunately due to the inside shape of the tank the dent is not accessible from inside. Anyone have experience with similar dents?

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It's been great fun getting to know the ins and outs of the bike by working on it, but more so by riding favorite local twisty roads!

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-Bill
 
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bobl

Well-known member
Beautiful work! One caveat that you might not encounter, but I did. The synthetic ATF leaked at both new fork seals. I blamed the seals, but read of a similar problem, Drained, cleaned, and refilled with fork oil, and no more leakage. I don't know if it was the seals or the oil, but they were incompatible. If both of yours seep, try different oil. Great work, wish I could send my beater to you for a refit!.
 

Aware

Well-known member
Beautifully done.

So tell us more about how it rides. I remember the CBR400RR fondly as a startlingly good bike, so the CB should be great too.
 

GB500guy

Well-known member
Beautiful work! One caveat that you might not encounter, but I did. The synthetic ATF leaked at both new fork seals. I blamed the seals, but read of a similar problem, Drained, cleaned, and refilled with fork oil, and no more leakage. I don't know if it was the seals or the oil, but they were incompatible. If both of yours seep, try different oil. Great work, wish I could send my beater to you for a refit!.

Interesting, I have had no problem using synth ATF in other bikes, but thanks for the heads-up!

-Bill
 

GB500guy

Well-known member
Beautifully done.

So tell us more about how it rides. I remember the CBR400RR fondly as a startlingly good bike, so the CB should be great too.

Thanks Steve. Never having owned a sport bike before I don't have a basis for comparison. But all I can say is this little screamer is a joy to ride. Smooth, light, feels very solid when cornering, and has more power than I will ever use. Despite the 13.5K redline, the usable power band is surprisingly wide. The engine is content to pull away from 30 mph in 6th gear with no complaint, then comes on really strong above 6-7K when the need for speed comes up. I really enjoy forgetting about shifting and just concentrating on corner lines. :party

-Bill
 

OaklandF4i

Darwin's exception
Fantastic job! I love projects like this and reading about them. :thumbup I've also always wanted a CB-1, GB500, and an NT650. From an era when Honda was still making interesting bikes.
 

Junkie

gone for now
I'm surprised that the shock has that much effective leverage on it - close to a 5:1 travel ratio is higher than most.

Most bikes run the speedo off the front sprocket. Front wheel is common too, though.
 

GB500guy

Well-known member
I'm surprised that the shock has that much effective leverage on it - close to a 5:1 travel ratio is higher than most.

Most bikes run the speedo off the front sprocket. Front wheel is common too, though.

Being a vintage bike guy that was new to me. I assume newer bikes use an electronic sensor on the countershaft instead of a cable?

-Bill
 

GB500guy

Well-known member
Well Done...

Were you an engineer or machinist?

Thanks, mechanical engineer by education, but never worked in the field. Just a lifelong workshop hobbiest, and former Honda dealership mechanic in the 1960s and 70s.

-Bill
 

Aware

Well-known member
Being a vintage bike guy that was new to me. I assume newer bikes use an electronic sensor on the countershaft instead of a cable?

-Bill

My CB1000F (similar vintage) also runs the speedo off the front sprocket.
 

RVFRick

Well-known member
Nice write-up, Bill! :thumbup

What's your process to spiff up fasteners?

I find a replacement Blackbird shock can you make me a Delrin bushing?
 

GB500guy

Well-known member
Nice write-up, Bill! :thumbup

What's your process to spiff up fasteners?

I find a replacement Blackbird shock can you make me a Delrin bushing?

Thanks Rick,

On some plain zinc plated nuts & bolts I just clean with an ultrasonic cleaner. If badly tarnished, I might chuck them up in the lathe (or a drill press works) and spin them against a Scotchbrite pad for a brushed finish, then clear coat. But on better plated bits I buff with a cotton wheel and a stick of Dico Tripoli compound. After buffing and cleaning with solvent, I may or may not clear coat.

PM coming on the shock question.

-Bill
 

berth

Well-known member
Shiny.

This is just more evidence to why people like me should not buy bikes like this.
 

RVFRick

Well-known member
Have you considered the hot melt glue technique to remove/minimize the tank dent? I think Harbor Freight sells a kit and Jeff Bezos certainly does. Easy enough to make your own. I have never tried it but looks like fun.
 
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