1975 Honda CB125 project

[nfo]

Hi all,

This is my first post here, so I'll try not to break too many house rules. Should I introduce myself somewhere? Quite a few pics but I've kept them to 640px.

Anyway, the story. Until recently I had no intention of getting into motorcycling, though I definitely liked the idea of puttering about the countryside on something old and British in a vague sort of way. A couple of things changed that - for one, a new housemate moved in, he's restoring a late 20s BSA 350cc side-valve single, and it looks pretty cool. 3-speed, hand gear change, total loss lubrication, 3.5 bhp.

Secondly, I got given a motorbike, which suddenly meant I had a project to get stuck into - as if I needed a distraction from my current task of writing up the last three and a half years' work. The bike is a 1975 CB125 single ('P' reg), which was last on the road in 2008. One of my colleagues owned it, and - not known for his mechanical sympathy - managed to melt the piston 'trying to overtake a lorry going up a hill'. He had a bigger bike by then, so after it sitting under a tarp in his garden for a while, he gave it to another of my colleagues who pulled the top end of the engine apart but then had far more pressing concerns (also writing up...).

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/DSCF6599.jpg
Last time it was together-ish.

Recently we were having a clearout, and amongst all sorts of other junk, there was the CB125. Somehow before long the suggestion that I might like to take it away to tinker with in my garage was raised, and turning down a free motorbike seemed like a bad idea. After all, it just needed a new piston (no other obvious damage having occured), MOT and with a CBT I could be pootling about all summer. I've spent plenty of time fiddling about with 4-wheeled machinery and pushbikes, so not too big a step. I love the way everything is accessible and obvious, no mysterious black boxes or hidden gubbins here.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/DSCF6576.jpg
27,746 miles

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120614_010711.jpg
1,850 miles/keeper

To begin with, I paid attention to the engine, which is now ready to go back togther - once I borrow or buy a suitable valve spring compressor - any suggestions for one that will definitely fit? Head, valves and bore are all cleaned up and it doesn't look too bad. More recently I got the bike back home and started poking about, thinking I'd just give it a bit of a clean and fix the things that were actually broken.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/DSCF6590.jpg
122cc of no power?

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/560284_996903038092_466309432_n-1.jpg
Head and barrel. Cam chain has worn a bit of a groove! Cam journals aren't too bad - not loose anyway.

First thing I did was apply some electrical juice and see if there was life. Hmm. Not promising - headlight more akin to a tealight, indicators seemingly completely random, and everything killed by putting the brake light on. Did a quick check and the tail light was acutally seeing about 3 V, with a good 6.5 V at the battery. Investigating the electrics further, it was clear that a mixture of corroded connections and a bit of previous-owner bodgery (did I mention that it's had 15 previous owners?!) was to blame. The individual parts are all OK, it's just the connections between them.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120531_120510.jpg
Electrical badness. Friend's comment: 'I've taxed worse'. He drives a Hillman Imp...

So, electrics being my thing, I decided to take it all apart and sort it out properly. Out came the 'loom' - if you can call a bundle of about 10 wires that - and before too long (after sitting on it going 'vroom' a bit), I'd started undoing every nut and bolt and taking all the non-electrical bits off too.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120618_221825-1.jpg
Box of electrical gubbins

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120614_094244.jpg
A bit crusty, but not ruinously so, I was expecting worse!

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/DSCF6594-1.jpg
Cleaned up much better than I expected, expect it will come back in no time though.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120616_091455.jpg
Don't intend to take it apart any further than this.

I guess the next thing was discovering a brand new tin of dulux black exterior gloss which came with the place I rent. Ah, perfect for touching up the frame. Or, as it turns out, completely repainting it.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120618_101416.jpg
Swing-arm, chain guard, rear brake torque arm cleaned up and ready to go back together

I should say now that my original aim was 'tatty but MOT'd and usable', which has now progressed towards 'presentable'. I'm not going for a perfect finish, and it's not a 'restoration' - more a fixing up and tidying up. At some point in the past a previous owner has sprayed quite a bit of the chrome with silver paint, so it's not in 'original' condition to begin with. Some degree of 'project creep' has set in but I'm trying to be sensible and leave easily-done cosmetic stuff until after it's up and running. Can't really clean up the frame with everything attached though, so best to do it now.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/DSCF6577.jpg
From this...

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120616_111944.jpg
...to this. The finish is a bit agricultural, but it looks alright from 6 feet away

But yes, so far I've stripped it back as far as I intend going and given the frame a couple of coats of paint - and I'm pretty pleased with how much better it looks already. Next is cleaning and refitting the frame parts, after which I'll deal with the electrics and get that all working. Finally, the engine will go back together and hopefully I'll have a running, MOT-ready bike. CBT booked for the end of the month, let's hope I enjoy being on 2 wheels with an engine! Even if not, it's been fun having a little project to tinker with.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120613_211259.jpg
Gunky switches

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120613_220144.jpg
All cleaned up. With 6 V electrics, can't afford to lose anything through crusty contacts.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120618_221915-1.jpg
Small but growing collection of 'sorted' bits waiting to go back on.

Dunno if anyone will be interested at all, but as it comes along I'll keep posting updates and I'm sure there will be questions, particularly once I'm trying to get it running. I've stripped and rebuilt lawnmower engines before, but they're easy - no timing, only one adjustment on the carb. It was running before, so my plan is to clean the carb but not touch any adjustments for now.

I've been led to expect barely enough power to pull the skin off a rice pudding and brakes to match, but a friend who recently bought something similar (after 10 years of car driving) described it as being both painfully slow but more than fast enough to be scary at the same time

[roadracejoe]

Brilliant !! i love reading about these rebuilds. Theres something very satisfying about saving a bike from being scrapped and lost forever Look forward to seeing the finished result, thanks for posting.

[blurredman]

Wow. You put some effort into the thread! And the said project itself of course

I did a similar thing a few years ago on my CG.

Just a pitty the bike isn't a pre-'73. Mind you, £16 isn't much these days

I'm enjoying this. MOAR!
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 50k.

[nfo]

[satelliteone]

WOW, liking the thread. Did an old CB125 couple of years ago, yours is deffo cleaner than the one i had.


https://www.bikechatforums.com/viewtopic.php?p=1334325

Looking good tho..
____________________
Honda XLR125R - Project
TZR125RR Belgarda 4DL - Sold
Chinki Project done n Dusted/sold** DTR125 2003 - Finished/sold

[nfo]

[blurredman]

Is that a 3" rear tyre I see? I have 2.75" on my rear on my CG, these small bikes look physically much better with a 3" tbh..

Yes you can use paint stripper, that is what I used on my CG engine.

By the way, after applying the paint to the engine, it may be worth putting heat resistent laquer on it too. Otherwise some paints can run off with petrol, or indeed dirt can bake to the paint which means it's impossible to get off without taking the paint off too
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 50k.

[nfo]

[blurredman]

[nfo]

Cool, cheers. Cleaning up the engine is not something I'm looking forward to - fiddly! Never part of the plan, but it would be a shame to put a manky engine into a nice clean frame

Heh, looks like fun. I can see lots of similar bits between your bike and mine, what age is it? I'd be interested to know if CG125 bits can be used on a CB125 as they seem to be more widely available. Front mudguard was the main one I had in mind...

EDIT: Also going to steal your L-plate mounting method. Looks much neater than the 'fork-mounted air-brake' arrangement.

EDIT 2: Just seen the extra pics. Are you quite tall, or is the bike just tiny?
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[nisp]

I don't trust nitromors anymore used a tin I had in the garage, it ran out, so I bought another one as you do and it is only usfull to drown ants, waist of £10



The best thing I have ever bought for doing that sort of thing is a sponge on a stick. see link

https://www.google.co.uk/products/catalog?q=abrasive+disc&oe=utf-8&rls=org.mozilla:en-GB:official&client=firefox-a&um=1&ie=UTF-8&tbm=shop&cid=11740984822213375558&sa=X&ei=FuHhT9ixAsvE8QPZ2pWPBA&ved=0CIMBEPICMAE
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Suzuki TS 50 1999 Honda CB 125 t2 1981 Yamaha XJ 600 s Diversion Honda cx 500 MZ ETZ 250 1985 Yamaha FZR 400 1981 Suzuki TS 185 1984 Triumph bonneville 790 2001 MZ TS250 1979 Suzuki sv 650 1999 KTM exc RFS 450 2007 Hercules mx 125 1976

[nfo]

[nisp]

I went down to b&Q for mine I was plundering the idea of more paint stripper but walked past and found a shelf dedicated to those babies. the wire brush on a stick might be a bit to harsh on a aluminium engine but you can get a softer sponge on a stick which will do wonders!
____________________
Suzuki TS 50 1999 Honda CB 125 t2 1981 Yamaha XJ 600 s Diversion Honda cx 500 MZ ETZ 250 1985 Yamaha FZR 400 1981 Suzuki TS 185 1984 Triumph bonneville 790 2001 MZ TS250 1979 Suzuki sv 650 1999 KTM exc RFS 450 2007 Hercules mx 125 1976

[blurredman]

[nfo]

Good point re: hitting the mudguard. Out of interest, how soft is the front of your CG? I've no point of reference, but I was surprised at the softness of the CB's front suspension. I don't know if it's tired or just a case of 'they all do that, sir'.

I did drain and refill the fork oil, what came out looked more like chocolate milk than anything with a right to call itself oil Didn't make it any less divey.
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[blurredman]

[nfo]

Ah, good to know. Something to fiddle about with I guess, I think the numbers in my Haynes were a bit different. Can't remember off the top of my head, but I 'calibrated' a plastic cup to get the right amount
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[Hobgoblin]

https://chzmemebase.files.wordpress.com/2011/11/internet-memes-if-you-fap-on-a-plane-are-you-hijacking.jpg
____________________
Plodding along on my CG

[nfo]

Pfft.
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[nfo]

Pfft. (Twice it would seem- no deleting?)
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[blurredman]

By the way, I've just noticed, your rear tyre says 17", but my CG tyres are all 18".. Is it a case of a smaller tyre somehow been fitted or that the obvious conclusion is the wheels themselves are smaller?
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 50k.

[nfo]

I can only conclude the same.
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[nfo]

Not very exciting, but it's back on its wheels, and whilst this terrible phone camera shot doesn't really show it, it does look smarter than before.
https://i278.photobucket.com/albums/kk83/no_bb/IMG_20120621_130838.jpg

I'm missing the left-hand plastic cover (which goes over the battery and 'tool box', does anyone know a good UK source for them? There are reproduction parts available from the far east via eBay but that's all I've found. Where the blue paint is chipped on the one I do have it's orange underneath, and the MOT history lookup records the colour of the bike as 'orange' last time it was tested

Anyway, not going to have time to work on it for a few days but hopefully it's now reached the point where the number of bits it's in starts decreasing
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...

[Fizzer Thou]

I had a CB125S back in '75 as my first ever bike.So this post brings back many many memories of stripping down engines,blown main fuses,strange engine noises,girlfriends wanting me to go faster even though I was flat-out,coming off the bike for the first time,running out of petrol on the A2 late at night with no money in my pocket,my first ever trip down to Hastings in the Summer of 1975,etc etc.

Keep up the good work.The more pics the better as they renew even more memories
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[nfo]

Not a very exciting update, but after a busy weekend I had some 'tinker time' in the garage last night

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120625_222937.jpg
Wiring loom completely stripped and cleaned. Electrical tape residue all gone, got new bullet connectors to replace the chocblock bodges I removed.

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120625_223049.jpg
Rear brake lever and spring refitted. The parts 'fiche indicates that the rear brake light switch spring is coaxial with the brake lever spring, but this doesn't make any sense on the bike

https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120625_222956.jpg
https://i278.photobucket.com/albums/kk83/no_bb/CB125-SML/IMG_20120625_223114.jpg
Finished repairing and cleaning up the handlebar switches, put it all together with a new throttle cable which actually moves

I think I've finally finished painting brackets (good!), starting to work through the box of bits removed from the bike. Turns out there was no foam in the air filter, hmm.

Need to get in an order from DSS/CMS/eBay. Presently debating splitting the crankcases to clean it all up as I'm a bit worried that there might be all sorts of crud floating around in there waiting to cause me trouble. What degree of fear should I have regarding this? I've got a Haynes book of lies, all the exploded parts diagrams and a camera...
____________________
Mar's Law: Everything is linear if plotted log-log with a fat magic marker.
1975 CB125S 'repair and tidy up' project thread here...