'73 CB125S Cafe

xb33bsa said:

no hagen would not be the top brand simply because they are unservicable you cannot refresh the oil or have the valving fine tuned
top shelf would be ohlins, fox or works performance, all servicable konis or ikons would be a good choice as well
it is a very light bike so you do need to get something that is sprung and valved accordingly
slightly longer is fine, like 1/2"

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Thanks for dropping some names to get me in the right direction. Not sure if I'm willing to drop top dollar on shocks for a $600 bike, but I'll read up and weigh that decision for myself!

spurlock said:

Longer shocks will drop the rear wheel a bit so just be sure that doesn't cause problems with the chain rubbing the top of the swing arm pivot at full extension. Also depending on tire sizes and front end mods you might end up with the center stand being too short to raise the rear wheel off the ground without a board under the stand.

-Bill

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Awesome , thanks! Might play it safe and just go with 330mm shocks to get a little bit more length and not mess with the rear end geometry too much!

Stock air box back in!



Pulled the spark plug out and found this:



Typically indicative that it was running rich air/fuel mixture, yes?



Was just double checking length on the stock clutch cable, and it seems like there is an issue. Pulling the cable is smooth and the clutch lever arm moves lovely, the problem is it won't return when the clutch is released. Without the cable it returns, but looks like the added weight/resistance stops it. I'm going to open up the crankcase cover tomorrow, but just looking for opinions from more knowledgable folks. Is this likely to be an issue with the cable, or whatever tensions the clutch lever arm?

Jesterhead said:

Pulled the spark plug out and found this:

Typically indicative that it was running rich air/fuel mixture, yes?

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Depends. Has the bike just been running in neutral in the garage or run a time or two around the block? If so that is normal plug color. You would only expect a tan color after running at high speed for a mile or more, then quickly stopped and the plug pulled. Otherwise when run under light load and never fully heated up the plug would always look black. Plug color is not really a good indicator of mixture, especially on simple carbureted engines.

Jesterhead said:

Was just double checking length on the stock clutch cable, and it seems like there is an issue. Pulling the cable is smooth and the clutch lever arm moves lovely, the problem is it won't return when the clutch is released. Without the cable it returns, but looks like the added weight/resistance stops it. I'm going to open up the crankcase cover tomorrow, but just looking for opinions from more knowledgable folks. Is this likely to be an issue with the cable, or whatever tensions the clutch lever arm?

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A couple of possibilities: Either the cable has internal drag from corrosion or disintegration of the poly cable liner (test by grabbing the cable outer in a padded vise and applying tension to each end of the cable inner and pulling back and forth), and if there is drag lube or replace the cable as needed. Or else the actuator cam inside the case is adjusted way wrong and over centering. Double check the adjustment screw/nut on the clutch cover just ahead of the foot peg as below:


Hope this helps,
-Bill

spurlock said:

Depends. Has the bike just been running in neutral in the garage or run a time or two around the block? If so that is normal plug color. You would only expect a tan color after running at high speed for a mile or more, then quickly stopped and the plug pulled. Otherwise when run under light load and never fully heated up the plug would always look black. Plug color is not really a good indicator of mixture, especially on simple carbureted engines.

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Nope, I've had this bike idling/running only in neutral for the past month, so it's never really been put through it's paces. Thanks!



Seems like my manual is missing that page on clutch adjustments. I'll check I'll that stuff tomorrow!

Nice bike......love these little things.

Looks great with the side panels back on. Sounds like internal cable friction on the clutch front.
Also check you are not asking it to cope with any radical bends along the way.

spurlock said:

A couple of possibilities: Either the cable has internal drag from corrosion or disintegration of the poly cable liner (test by grabbing the cable outer in a padded vise and applying tension to each end of the cable inner and pulling back and forth), and if there is drag lube or replace the cable as needed. Or else the actuator cam inside the case is adjusted way wrong and over centering. Double check the adjustment screw/nut on the clutch cover just ahead of the foot peg as below:

Hope this helps,
-Bill

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Was messing with adjustment screw and have it set to as much tension as possible. It returns fine and snappy without the cable. But with the cable its noticeably less snappy, and once it's on the lever it just won't return.

Definitely looks like friction in the clutch cable. I was contemplating buying a whole new set of cables any way. So looks like this made the decision for me.

Also had the crankcase cover off, and the gaskets are just about disintegrated. Looks like I'll be replacing those as well haha!

So still not entirely sure where the issue is with the clutch. I've lubed up the stock cable and it's buttery smooth when it's free. The clutch lever now weakly/barely returns when I release it. Any one have any other tips where to look?

Got a few gremlins like this to work out before I can send the frame to be sandblasted and powder coated!

Jesterhead said:

So still not entirely sure where the issue is with the clutch. I've lubed up the stock cable and it's buttery smooth when it's free. The clutch lever now weakly/barely returns when I release it. Any one have any other tips where to look?

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Disconnect the cable at the bottom end, then move the clutch case arm through its range with a wrench like below. It should feel very smooth in both directions:



Then hook a cord or wire to the clutch case arm and, leading it up in the same direction the cable would pull, attach a spring scale to the end. On my bike it takes about 32-34 lbs to start to move the arm.



If these checks are OK then just replace the cable and be done with it. Also you mentioned adjusting the case adj. screw "as tight as possible." Not sure what you mean by that, but the adj. screw is used to set the position of the clutch arm according to the mark on the case. That way the internal cam and lever arm have the correct geometry. Disconnect the cable at the bottom, then hold the arm lightly upward until you feel resistance. At that point the pivot pin on the end of the arm should be centered on the cast-in pointer on the case. Adjust the screw if needed to achieve this alignment, do not just tighten it for no reason.

-Bill

OK, so if you're talking 30+ lbs on your clutch arm. There's definitely something up with mine. Mine is nice and smooth through the entire range, but it's maybe 10 lbs of resistence max, consistently though it's movement.

Something up with the clutch itself I'm thinking now. Going to pull the crankcase cover off and try to investigate.

Thanks for those photos, Spurlock. Alway appreciate the help!

Jesterhead said:

OK, so if you're talking 30+ lbs on your clutch arm. There's definitely something up with mine. Mine is nice and smooth through the entire range, but it's maybe 10 lbs of resistence max, consistently though it's movement.

Something up with the clutch itself I'm thinking now. Going to pull the crankcase cover off and try to investigate.

Thanks for those photos, Spurlock. Alway appreciate the help!

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Sounds like your clutch pack springs are worn out. But keep in mind that the lever reduces a lot of the spring load, so it won't be the full 30+# at the lever. But it shouldn't be soft either.

High On Octane said:

Sounds like your clutch pack springs are worn out. But keep in mind that the lever reduces a lot of the spring load, so it won't be the full 30+# at the lever. But it shouldn't be soft either.

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Thanks!

Out of time for this weekend, so I'll dig through the net through the week and start checking it out next weekend.

Thanks again for all the help guys.

I can't imagine anything could make the springs lose that much tension, they have a very easy life. I'm wondering if someone has removed 2 of the four springs, or replaced them with incorrect springs. The shop manual does not give a spec on spring length but maybe someone here can provide that info, it would be something worth checking along with spring tension. If you can get hold of an original spring just set a bathroom scale on a drill press table, then compress the spring a fixed amount and note the scale reading. Compare to your existing springs.

Have you had the bike running enough to actually ride it? If so I would assume the clutch slips like crazy under load.

-Bill

spurlock said:

I can't imagine anything could make the springs lose that much tension, they have a very easy life. I'm wondering if someone has removed 2 of the four springs, or replaced them with incorrect springs. The shop manual does not give a spec on spring length but maybe someone here can provide that info, it would be something worth checking along with spring tension. If you can get hold of an original spring just set a bathroom scale on a drill press table, then compress the spring a fixed amount and note the scale reading. Compare to your existing springs.

Have you had the bike running enough to actually ride it? If so I would assume the clutch slips like crazy under load.

-Bill

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Peeked under the cover quickly and the are indeed 4 springs at least. I'll check what kind of tension they have once I get them out.

I've had the bike running back in the fall, but only just idling in a garage. Tyres/brakes/battery weren't fit to ride.

Looking quickly it seems like the clutch isn't disengaging properly. Like the plates aren't separating or something is holding them from separating. Will have more info once I have more time.