chain sizes for early bikes

[Bevel bob]

Having some issues working on a 1960 Italian Bike . the 420 chain i bought seems to be about half a mm to short in the pitch , after about 5 pitches the chain rides up on the sprocket. Any idea whats happening ? seems like the sprocket pitch is 12mm and chain 12.5 mm or 1/2". Do early italian bikes use a metric size ??

[themoudie]

Aye Bob,

Does the attached link below help you to sort out your chain size requirement?

Motorcycle_chain_size_dimensions

I am not ofay, with 1960's (assume Motobi?) chain/sprocket relationships. However, I would suggest that you get on the blower on Monday and have a word with "The Chain-man" link:

The Chain-man

In my experience, he has been very helpful, with supplying chains for the 450, whilst I obtain my sprockets from Nigel. Maybe a call to Talon sprockets?

I hope this helps, with the conundrum.

Good health, Bill

[Andy Higham]

As far as I know there is no chain made with a 12mm pitch. The only metric pitches are 03B = 5mm, 04B = 6mm and 05B = 8mm

[George]

I have owned Moto Guzzi, Mondial, Ducati and MZ all had imperial chains 1/2"

[Bevel bob]

Not got to the bottom of this yet ! , could be a rogue sprocket ?

[George]

Have you checked pitch on front sprocket

[Bevel bob]

Not yet George, some dismantling needed and we wanted to ride the bike a few times before the winter layup . Plenty of serious issues ,Forks totally worn out, wrong and worn carb, brake linings badly worn,,clapped out chain, draggy clutch with wrong parts, no battery box. motor solidly blocked with carbon , blown incorrect exhaust flange , leaky valve ,broken valve adjuster, wrong points .wrong timing, lights part working, faulty condensor, glazed bore or stuck /wrong rings, Worn out primary gear. Center stand an inch too long,Wrong gearing, raised when it should have been std or lowered, Nothing much then !! Looks really good though.(all fur coat!)

[George]

Hi Bob,PM sent

[Bevel bob]

After much experimental fiddling with ignition timings and modifying the advance unit the Catria now starts and feels responsive. Once the non sealing piston rings are either bedded in or replaced the bike will be viable. Had to back off the timing about 10 degrees from standard , I think these early bikes were expected to run on 72 octane or similar which needed a lot of advance. Todays fuel burns a lot faster i think .