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CB500 Four K1

36K views 291 replies 24 participants last post by  TrialsRider 
#1 ·
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Bought this on eBay. Got this far via a disk cutter and couple of sketchy seat mock ups. Not sure about either.
 
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#170 ·
Finally found some time and bad news. Cylinder 4 is really rough at the top. I could actually scratch the glaze off. Matching piston looks fine and as others where bores are ok and no lips. Rings are within tolerance.

Any thoughts or is this one for the machine shop?
 

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#173 ·
Still making progress and taking things apart.

In the process of splitting the cases. Does anyone know what this is/was that I found in the sump?

Feels like ‘spring’ steel and clearly a piece with some purpose that looks like about 40% of what it was.

Thanks.
 

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#179 ·
Thanks both for the response on this one. I've been through the exploded engine/gearbox drawings and can't see anything else it could be so feeler gauge it is/was.

I'm going to split the casing this w/e.

At what stage do I remove the big nut on top which has a spring loaded ball onto the fork shaft. Before or after splitting the casing?

Thanks.
 
#180 ·
Why are you splitting the cases? Given the condition of your top end, I have no reason to suspect that there are any issues with your rod or main bearings. How did the oil look? Any indication of bearing material in the oil or filter. I would stop making work for yourself. Have you reached a conclusion on the pitting in #4 cylinder? Is the pitting in the swept area of the rings at TDC? If it is, you need a bore job. If it is not, then I would consider a fresh hone of the cylinders and button it back up.
But, I have not yet commented on this and with the perspective now that goes all the way back to the beginning I will make some observations and comments based on experience rather than speculation. Along the way, I will disagree with almost all of what Trials rider has speculated on. My experience is that we (my brother and I) built a 75 550 into a successful roadrace bike when it was a current model which we both raced. It had an Action Fours 590 kit, Jerry Branch ported head, Action Fours cam and valve springs, CB750 K0 carbs and an Action Fours 4-1 pipe. We never had it on a dyno, but at Road America, down the back straight heading into turn 5, it could stay in the draft of a stock motored GS1000 with a pipe. For suspension we had Boge Mulholland SS1225 shocks with heavier oil in the rear, bronze swingarm bushings and rebuilt stock forks with Cerriani tubes. It had double front brakes using Honda components and SBS pads with a Goldwing M/C. We were runing Lester wheels and Dunlop slicks. I don't know of anyone else who has built and raced one.

First, I think your monoshock will work adequately, but will not be any better than the oem set-up would have been with good shocks.
The dual disc set up using Honda components and good brake pads, EBC, Ferodo or SBS will be more than you need on the street.
Even under hard braking, we did not notice any flex of the stock steering neck. We did have tapered rollers instead of the stock loose balls.
The chassis did flex a little under cornering, but everything flexed to one degree or another back then on the race track.

I think what you are doing will be fine, but be prepared to change things once (if) you get it on the street to get your suspension working well. I would not have done it in the sequence you are doing it, but I hope it works for you.
 
#181 ·
Kenessex

Thanks for the advice.

With regards to splitting the cases it's a fault that dates back to when I was kid 8, 9 years old. I started taking watches, cameras (not digital obviously), upright pianos apart. Pretty much anything made of two or more pieces. Migrated to engines, boxes, diffs etc. I've never got out of the habit of wanting to know how things work.

Nothing sparkling in the oil (apart from the feeler gauge) but the primary chain feels very slack. I need to find the tolerances. I've not faced into the cylinders but I like the below top ring thought and a glaze bust. Wouldn't that be good news.

I'm committed to the monoshock as earlier and realistic enough to figure on some development. Couldn't bring myself to do the GXSR front end but if tapered bearings add then happy to go with that.

Is there a thread for your build I can check out?

Thanks
 
#182 ·
Sorry jumped a bit soon, just noticed your build was back in the day.

Sounds like a monster.

Clear on the pads and I have GW large bore master cylinder. Sorry to loose the ali reservoir however.

I saw one Lester rim on eBay but let it go at this stage.

Anyone know what these wheels are?

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#191 ·
S

Anyone know what these wheels are?

Thanks. View attachment 95119
Front looks like a Lester or a Morris. Can't see if the spoke is single rib or double rib. If it's lester, I agree with ken. If it's a morris they are much lighter and nice period wheels. The rear looks like a henry abe star mag. There are lots of old 70's mag wheels that work well. I don't know what your rear axle size is (if it is the same as a cb750 or not) but honda used the same rear axle size on their bikes until the early 2000s. CBR600F2s and F3s have the same rear axle diameter as 1969 cb750s, so do some interceptors, and other bikes. consult a rear wheel bearing chart but it makes rear wheel swapping more interesting. I like the 80's interceptor wheels because they look like old dymag racing wheels.
 
#183 ·
Those look like Lesters. I do not recommend them. Back in the day they were cool, but they were heavy and narrow. I think for current technology I would just lace up some wider 18" alloy rims to the stock hubs with some heavy duty stainless spokes. There are plenty of good 18" tires available now including decent race rubber. Our 550 back then was pretty good, but if I were building it again I would get better shocks, a braced swingarm, better brakes and larger diameter fork tubes.

If you are going to use the forks and brakes that you have, then for sure reverse the fork legs and mount the calipers behind the legs. Thinning and drilling the discs is a very good idea to reduce unsprung weight. If you want to keep the stock front fender, you can drill out the rivets, reverse the fender on the mounting bracket and use small screws to remount it.

BTW, looking at your valve seats, they are a little wider then I generally made them. I have a tendency to make them on the narrowest side of the spec and move them as close to the outer edge of the valve as I can. They don't last as long before needing a refresh, but they do maximize your available valve area.
 
#184 ·
Thanks for the advice.

The Lesters do look good and my current wheels are shot. Just looking for options.

Any idea how wide rims I can sensibly run front and back?

Also the following questions:

1. Why the change from 19” to 18” front wheel?

2. Why reverse the callipers? Sure to look better but can I still run a cable tach from the origin side?

3. What do I get from reversing the front fender?

Just need to find someone for drilling disks (and head).

Thanks.
 
#185 ·
you probably need frender reversed on reversed bracket with reversed fork sliders see
valve seats def too wide
which can be a problem on the exhast valve as it is then easier for a piece of carbon to build up ,which can lead to burnt ex valve
how is the valve to stem clearance ?
contrary to what trials rider is saying the smaller the master cylinder the more power it has
but a small bore moves less volume so it cannot keep up with 2 clappers
 
#186 ·
the design fault of the early cb calipers lies in the fitment of the friction pad directly to a counterbore coaxial to the piston bore
it is a piss poor way to tranmit the thrust from the disc friction
heat is directly soaked into the caliper casting
AND it allows heat to be absorbed by the caliper at high rate
after all brakes are simply converting kinectic energy to heat energy ,friction being the converter
on to the wheels
lacing in alloy rims will only save weight if you do not use "heavy duty " ss spokes
ss spokes are not as strong as steel spokes
using heavier parts than needed is counterproductive
stick with butted steel spokes of the same gauge as stock
the front hub can have the center section machined off
rear hub and brake plate can be ventilated to save a few ounces
i would go 1 size wider on the rims ,one tire size wider
18 in the front i guess more tire selection in that size

do not be a moron clown and mount the fattest tire possible
those big fat tires look queer and only show the stupidity of the moron that built the bike
use aluminum nipples
 
#187 ·
I will defer to XB's expertise on wheels and spokes. I wouldn't worry about saving a few ounces anywhere since it isn't a race bike. Just lace up some alloy rims with whatever spokes. Iwould get them from Buchanans, because they will have what you need. I would run a WM3 front and a WM 5 rear in 18 with a 100 -18 front tire and a 130 18 rear. You could go 1 size wider if you wanted to, but it would slow up your steering in the front and the rear might not fit in the swingarm. You canget lots of good tires, all the way to race compound rubber if you want in both 18 and 19, but the selection is much better in 18.
XB is also right about the Honda single piston caliper design, however it is period and the dual disc setup with drilled and thinned rotors, when adjusted correctly, will work more than adequately on the street. It is what I would do on this bike.
 
#188 · (Edited)
:/ they all look pretty sketchy from here, but then Suzuki never was world renown for fitting their regular bikes with world class suspension components.

imho forks that have no slide bushings is an economical design to get the thing out the door, not a performance sales feature. If anything needs to be measured for service wear it would be the inside bore of the lower fork legs, they are aluminum and your stanchions are steel, in that scenario no wear on the stanchions is expected but the bore in the lower fork legs might wear out of round with age, frequent replacement of the fork oil would have been a wise move but fairly obvious these forks were used with no love.


... and now the rest of the thread shows up and posters names are blank :confused: something is really messed up with this website today, apologies if I just responded to an old post.
 
#192 ·
Been a bit delayed by new metalwork but can’t afford to lose the $5 bet that this bike will run again, so a few updates.

Still going backwards obviously.

Twin discs, new rims (on their way), knee dents to the tank, a bit of not too shiny polishing and rebore underway.
 

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#194 · (Edited)
I would have thought that given what they charge for doing that, they could at least purchase a better selection of screws so they don't poke though the other side. I know its not a big deal, but the surgeon is not building a frigging birdhouse (assuming he/she could actually build one). Is that your boys starting to glow from the radiation or is that just a reflection?
 
#197 · (Edited)
I would have thought that given what they charge for doing that, they could at least purchase a better selection of screws so they don't poke though the other side. I know its not a big deal, but he's not building a frigging birdhouse (assuming he could actually build one). Is that your boys starting to glow from the radiation or is that just a reflection?
All done for free on the National Health Service in UK, if you ignore the outrageous taxes.

What she lacked in accuracy, she made up for with enthusiasm.

The staples were clearly done blindfold. Skin Arm Joint Human leg Shoulder
 
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