CB125S Blues

tarmac man · L Plate Warrior Joined: 23 Oct 2022 Karma :

Hi Everyone,
I am new to this forum and am looking for some tech advice please.
A few months ago my son purchased an early 70's Honda CB125s.
The kickstart broke and went loose, which entailed an expensive strip and rebuild. On installing the rebuilt engine yesterday, the kickstart broke yet again. he has sunk a lot of money into the bike, what would possibly cause this?
Would a CG125 engine also fit this bike....just to get him up and running?
Thanks in advance

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Sounds like assembly error or you overlooked something
so options are:
Go back in and sort it
Spend dosh on another old engine of unknown quality
Spend lotsa dosh on a rebuilt engine with warranty (if available)
Even a ropey old CG is a 'classic' nowadays so premium prices may apply sadly.
( motorcycles = cheap motoring my arse)
As I'm no purist I'd dump the 6V, points ignition, kick start only
stuff and upgrade it to a 12V, CDI, leccy start bike
and grab a good used chinese clone lump for it
156/157FMI types come to mind which I believe are Honda clones
but not 100% sure.

It's easy enough as long as you understand the electrical and
ignitions systems well enough to do the mods.
____________________
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stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Which part of the kickstart broke?
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tarmac man · L Plate Warrior Joined: 23 Oct 2022 Karma :

Hi,
Not sure which part/s broke, but apparently teeth were missing. Whole new gearbox assembly sourced and affected parts were replaced. Strange that the kickstart won't engage now.

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

In which case, I'll go with WD Forte in that it's probably been put together wrong.

Kickstart pawls are tricksy things at the best of times, you have to assemble springs under tension and jiggle things together into the correct place without small sprung pins/flaps pinging off into the corner of the workshop.

I'm not very familiar with how it's done on that exact model but I remember the one on a CB125T taking me 3 or 4 gos to get in correctly. I'd make my customary bet of 25p that he's assembled it in the wrong position so it's not engaging the stop at the end of travel and the starter quadrant has over-rotated. Might even be that the stop was broken/missing to begin with which caused the original problem. Or possibly he hasn't got the return spring tensioned and inserted correctly.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

tarmac man · L Plate Warrior Joined: 23 Oct 2022 Karma :

Hi Guys,
The bike went back to the dealer who stripped the gearbox again only to say the 'idler gear' had gone once again with teeth missing. Same issue as last time apparently. I assume that there is something misaligned and causing undue stress on the broken part??

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

tarmac man · L Plate Warrior Joined: 23 Oct 2022 Karma :

Hi,
The dealer is puzzled but has kindly elected to strip and rebuild the motor for free (excluding the broken part) It is strange though, as the same thing has happened twice...suggestive of a gearbox fault other than the new part?? Anyway, thanks very much for your input...will let you know how we get on.
Cheers

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

Presumably it stripped whilst you were trying to start it? If you can push it along easily in neutral it's not a gearbox fault.

Always assuming it's not got a siezed engine....
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Sprint ST 1050

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

Wow, clips and washers etc in the wrong place can/will cause gear problems.

Get your mech to check the CMSNL exploded views to make sure all the components are in the correct place.

A new gasket set would be needed also. No sealer ( that's NO SEALER ) used or needed on this engine particularly on the clutch cover which had very important oil ways !

Still don't know if this bike engine is the solid head or split head type. What year is the bike ?
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nuts about bikes