Chunky’s 1971 CB125S

[Chunky_t]

Hey guys, 

decided to make a thread for this bike, built an entire 140 powered FR and neglected to make one so thought I had better make one for this. 
Bought of marketplace at a decent price as a ‘ran when parked’ type scenario. Everything was there and it actually ran after a carb clean and unblocking the pilot jet.
Here it is in all its crusty glory (along with the FR) 

plan is to get it all legal then drop an XR200 donk in it eventually. 
I have also discovered it has cam journal wear so the cam has play in the head, so will need to do some kind of roller bearing mod to remedy that. 
Other points to fix are that it exploded every light bulb installed, it has an un sightly Chinese barrel on it, and the clutch slips. 

[Chunky_t]

Haven't achieved a whole lot on this thing yet, took the engine out and inspected the insides, appears the piston had been getting a little friendly with the head on the intake side (my guess is that since it's chinga gear the casting may not be perfect) so just cleaned up the piston a little so hopefully should clear now.

Cleaned it up a little while it was on the bench, came up pretty well for a small amount of work. 

Also ran my multi meter over a couple of bits as per the manual and the Rectifier is toast, and appears the front brake switch isn't working either. It seems that the right hand switch block/lever may not be the original one either.

[Chunky_t]

Reviving this thread, haven't done as much as I'd like with this bike. 

Have since discovered it's a 1971 model, imported into nz in 73. Also got permission to reuse the black plate on it - complete with rego and wof from 1984. 

The original tank on it was completely toast, had been previously lined and that had started to fail, exposing some rust holes and paper thin steel on the top of the tank. 

Amazingly found a cb125s tank on trademe listed as a 'Honda tank' so managed to nab that for $50. However it wasn't without its own problems, here it is after sanding: 

and after some work it's now looking like this: 

I got a few new shiny parts to chuck on so will add some photos of it complete once those are all on. Tank doesn't look bad for one big sticker! 

[GregT]

Have you got around to the cam bearing wear yet ?  Usually it's the inner end which wears worse. Usually fixed by machining the cam end down about 2mm OD. then a bronze bush turned up to fit the head and be about .002in clearance on the reduced cam end. A 5mm roll pin inserted in the head and a matching hole drilled in the bush to peg it in place and the job's done.

Did a few of them back in the day.

[Chunky_t]

No never got around to it - it had been making a clattering sound under load when riding it which i thought was related to the cam, but I tore the top end down for a look and the piston casting sucks and was touching the head in one little section. Filed the piston to fix that up. 

I also fired it up for the first time in probably 18 months after getting the new tank on and now it pisses oil from the head gasket around one of the studs. Runs good, and sounds great for a little donk. Just running a total loss oil system now, apparently. 

Wrapped the side covers to match the tank. Job tidy jim 

Oh and upgraded to the world's highest performing tyre; the ppsc control tyre - the shinko 241, naturally. 

 

 

[Chunky_t]

Today the local honda dealership here had what they called a 'showcase' to celebrate 50 years of honda in marlborough so I took my bike along - some quite cool old bikes came out of the woodwork & I got some free shit from the dealer for my troubles. Job tidy. 

Couple of the highlights; 

 

 

 

[Chunky_t]

After some contemplation about fixing the head gasket weeing oil problem I have come up with the solution: 

I had planned to put this in later but why not now? Lol. 

It's actually an XL185 engine with an xr top end, but with something weird like a ctx200 piston I think. So needs a little love but nothing major.