Eyup from an old git

[KrazeyOldGit]

Been riding on and off for around 30 years and just started my first project bike. Talk about a midlife crisis  Living in God's Own County , Yorkshire and wondering why on earth I thought trying to rebuild a bike that's only 10 years younger than me was a good idea. Hoping to get some inspiration and maybe advice from more experienced folks on here.
 The bike I'm trying to get back on the road? A 1978 CB125 B6 twin aka CB125 JX Benley. Never released in UK or USA , believe mine was imported from Germany altho I don't know when. It was first registered in UK January 2023 and I'm the second owner since then.

[billysugger]

Hi KOG, welcome to the forum.

For spares I would try David Silvers.

A lot of parts for the twins are no longer available, especially things like airbox to carb rubbers. On my twin I had to improvise, using water heater hose meant for a car. Pistons and valves are still around as are valve guides, seals etc. 

If needing a new barrel avoid the cheap Chinese made copies. They are a generic type and don't have all the necessary holes in the right places. In your pic it actually looks a decent bike, so enjoy it

[Simon Davey]

Hi @KrazeyOldGit, and welcome to the forum. 

There's nothing like an easy project to get on with, and that's nothing like an easy project

To be fair though, it looks proper tidy. 

[KrazeyOldGit]

2 hours ago, billysugger said:

Hi KOG, welcome to the forum.

For spares I would try David Silvers.

A lot of parts for the twins are no longer available, especially things like airbox to carb rubbers. On my twin I had to improvise, using water heater hose meant for a car. Pistons and valves are still around as are valve guides, seals etc. 

If needing a new barrel avoid the cheap Chinese made copies. They are a generic type and don't have all the necessary holes in the right places. In your pic it actually looks a decent bike, so enjoy it

In all honesty I've given up on David Silvers , they don't even list my bike
 For the most part she looked good but almost every bolt/screw is rounded/stripped and the engine was a mess with re-used broken gaskets, half a gallon of sealant and pitting in the combustion chamber from moisture deposits. Not to mention someone had tried running the 6 volt system on a 12 volt battery. So far I've spent around £600 just on engine and electrical stuff, most of which has ended up coming from Indonesia. It would have been nearer £800 if I'd gone to CMNSL . I'm praying my attempt at polishing out the internal pitting has worked as I simply can not afford the minimum of £1700 for a replacement head (CMNSL actually want nearer to £2.5k for one!) at the moment . Saving for one would take at least 6 months  
 Currently waiting on valves coming from somewhere over seas before I can rebuild the motor. Then it's time to try and figure out why the headlight blinks along with the turn signals.. 

[billysugger]

The turn signals and headlight blinking together is a faulty earth connection, as, if I remember correctly, they use the same earth point.

[Old and Withered]

A lot of Japanese bikes of this time used common parts so although the bike may not be listed if you can find a part number list for your bike. Pop the part number in Google and even the vaguest of things will turn up. The photo you have posted (lovely bike by the way) the barrels and head looks disproportionately small for the bottom end and the bike itself looks quite similar to the cb200 of that era.

[KrazeyOldGit]

On 05/05/2025 at 19:02, Old and Withered said:

A lot of Japanese bikes of this time used common parts so although the bike may not be listed if you can find a part number list for your bike. Pop the part number in Google and even the vaguest of things will turn up. The photo you have posted (lovely bike by the way) the barrels and head looks disproportionately small for the bottom end and the bike itself looks quite similar to the cb200 of that era.

 It does have a lot of similarities with the 200 , the tank and cable operated front disc brake being the most obvious but it has left side cam chain engine. The closest to it is the CB125 K5 but there is a difference in the external shape of the cylinder head which was only used on this one model. The K5 had a rounded cam chain chamber and points cover. On the B6 they're more square so a different head would mean different points and tacho covers etc.  As best as I can tell from image comparisons its the only difference in the K5 and B6 engines.