Topic: This weekend I'm picking up a 1980 CB125 for 100 bucks. Pretty excited

[Pielz]

I'm glad to hear that you have the bike on the road,running it through the gears  .That fuel tank door over the cap is a little finicky.. there's a type of metal spring/tab in there that you can slowly bend to tighten-up how much tension is applied to the door;I hope it hasn't snapped off in a previous life.How is the break-in coming along on your engine,change the oil and running it hard ?

Running it very hard! I'll look in to bending that tab back. It's still there fortunately lol. I've been running it through it's paces pretty hard. Up and downhill trying to match where it says to shift on the speedo. I kinda wish it had a tach but it is what it is. I've gotta grab another quart of oil for another change soon. It'll be an instructional change to show my mom considering it's kinda her bike to learn on!

[grcamna2]

I use Shell Rotella T4 15/40 truck oil because it has the additives for the wet clutch,etc. and I can buy 4) qts.(at Wally World) for less than 2) qts. of motorcycle engine oil at the dealers and get 4) oil changes from it.

[Pielz]

I use Shell Rotella T4 15/40 truck oil because it has the additives for the wet clutch,etc. and I can buy 4) qts.(at Wally World) for less than 2) qts. of motorcycle engine oil at the dealers and get 4) oil changes from it.

That's what I've been using in it! The t4. I've had good luck with the t6 synthetic in my 750. I like knowing the synthetic doesn't break down as fast especially since it's air-cooled and might get a little hot at long stoplights and whatnot

[Pielz]

This afternoon I was out putting it through the paces doing some spirited laps around my neighborhood and the bolt attaching the brake drum to the rod that holds it in place rattled loose. I may have forgot a cotter pin.. but all's good, the actuator rod bent a bit but I rode it home. Just gotta straighten it out and reattach it. Glad I was only going like 15 mph when it happened that's my bad. Coincidentally it happened just a few days after another guy posted about it happening to him on the highway.

[grcamna2]

This afternoon I was out putting it through the paces doing some spirited laps around my neighborhood and the bolt attaching the brake drum to the rod that holds it in place rattled loose. I may have forgot a cotter pin.. but all's good, the actuator rod bent a bit but I rode it home. Just gotta straighten it out and reattach it. Glad I was only going like 15 mph when it happened that's my bad. Coincidentally it happened just a few days after another guy posted about it happening to him on the highway.

ouch  Good thing not much harm.I'm glad to hear you're running the bike.Working on them is nice but riding them is Much better.

[Pielz]

I'll tell you what, going from riding that 125 to my 750 makes it feel like a diesel truck lol. The 125 is so light and flickable like a bicycle. My 750 is kinda agile but it's so top heavy. It took a second for me to readjust.

[grcamna2]

I'll tell you what, going from riding that 125 to my 750 makes it feel like a diesel truck lol. The 125 is so light and flickable like a bicycle. My 750 is kinda agile but it's so top heavy. It took a second for me to readjust.

How's the engine sound now,did the cam chain adjustment take care of that noise ?

[Pielz]

It's not too bad. Still a little tappy sounding but I haven't done a tappet adjustment since I've had it running. I also think the timing is also not perfect. I used a timing strobe and adjusting the points plate didn't seem to make a big difference it's still a little advanced so I think I'm still losing some power.

I'll go back to try it again soon.

[grcamna2]

Your dwell may have change as the points wear a bit too,changes how it powers-up.

[Pielz]

The points are brand new so it's possible they need dwell adjusted again. I may have messed up haha

[grcamna2]

The points are brand new so it's possible they need dwell adjusted again. I may have messed up haha

The lube for the points 'felt' at the bottom of the points cam likes a certain oil(not sure what's highly recommended)rather than grease,from what I remember in previous discussions here.. Clean the contact surfaces with a fresh currency ($1) bill,they're excellent paper and won't leave any lint after smoothing/dressing the surfaces lightly with Fine red Crocus Cloth,imo.

[Pielz]

I believe I lubed it with 3in1 oil. I'll go in and clean those up and see what I can get figured out

[grcamna2]

I believe I lubed it with 3in1 oil. I'll go in and clean those up and see what I can get figured out

3in1 is way to light.,you may need to remove the points and clean them down with contact cleaner.

[Pielz]

No prob, I've got a can. I'll do some research!

[Pielz]

Finally got a headlight! Bar lock and ignition are in the mail. It looks a lot nicer. Significantly more complete. Headlight was cheap. Like 12 dollars cheap. If it works it'll be worth every dollar lol. If not it does make it look nice in the meantime

[grcamna2]

What type of headlight bulb is it? Your stator feeds that headlight circuit 6vts. AC

[Pielz]

It's just some random thing from eBay but it'll work with 6v. And if I put one of the led h4 bulbs I have in there it should draw less power and be brighter

[grcamna2]

It's just some random thing from eBay but it'll work with 6v. And if I put one of the led h4 bulbs I have in there it should draw less power and be brighter

The LED will blow on you,they hate AC.I installed an inline(the power feed wire running from the headlight coil on your stator to the left hand switch:high-low beam) AC 12vt regulator and run a 12vt 35wt. H4 bulb,it doesn't mind AC to power it.

[Pielz]

Does the headlight circuit not go through the rectifier?

[grcamna2]

Does the headlight circuit not go through the rectifier?

Oh,
I just looked,well then your headlight may be good as it doesn't look to be direct to the switch from the stator like mine or the XL185 engine I use.Can you turn your headlight on without the engine running just by turning on the key ?

[Pielz]

I'm not actually sure cause it hadn't had a headlight until today lol. I'll check my wiring diagram and get back to you when I work on it a little tomorrow!

[grcamna2]

I'm not actually sure cause it hadn't had a headlight until today lol. I'll check my wiring diagram and get back to you when I work on it a little tomorrow!

The only diagram I have is that one I texted to you with the black smudge in the ink right where the color of the headlight wire from the switch should be.The headlight power wire on the left oem hand switch should be the black/white wire with a small black plastic piece of tube near the connector to where it will connect to a common black wire from the harness.Solid black wires on your harness are positive + connections for lights,etc.

[Pielz]

Here's the wiring diagram I have. It's specifically for the 79 and 80 years

[grcamna2]

Haynes

[Pielz]

So I might need someone smarter than me here but I'm looking at this diagram and it's looking like the headlight's power does in fact get filtered through the rectifier and converted to DC. I'm seeing all output from the alternator going through the rectifier. Is that right? Also I wonder if it'd be a good idea to put a regulator rectifier combo unit on it? Is that an option since it doesn't have a regulator from factory?
 
Also a bunch of places online list it as Regulator/Rectifier even when searched with the Honda part number 31700-102-731. I'm bad with electrical systems to begin with so this is kinda rough for me trying to parse this info. Especially on a bike with very limited support online.
 
Oh also my headlight has a high/low switch. There's no off. I'm guessing that means it's not on a separate circuit?