This is probably a really dumb question but I am new to Pre65's (Last brit bike I owned was in 1980) How do the imperial chain sizes compare to metric?, by BSA chain looks to be about 428, does that seem right?.

Also I have put an NGK plug in (equivalent to a champion N3) but it seems very loose in the threads antil the last turn, any ideas?.

Ta in advance.

The Imperial equivalant of 428 chain is I think 1/2 x 5/16 for good advice try Sprockets Unlimited their email is astrosprox@btinternet.com

Cannot help with the plug as usually they are a direct replacement check the thread it can be Helicoiled to repair it.

What is the bike ?

It's a genuine C15t and still completely original, I was going to build a special out of bits but this turned up. Trouble is as it is so original I don't want to mod it too much (although I will change the 20inch front wheel).

Sounds an interesting project, take lots of photos including close ups of everything before you start work and throw nothing away save everything it can always go back on again later.

If you want to ride it it needs to run well so the ignition needs to be just so as well as the carb.

Do not have any experience of the BSAs but I think many people run the PVL ign. system.

Good luck.

PVL ignition is fantastic once fitted properly, starts 1st kick whatever the circumstances, its only vice is the cost and the machining that has to be done to fit it

Boyer is cheaper, needs no machining (i Think)and i'm not aware of any failures but i've never ridden a bike with it.

oops forgot your plug question ...

sounds like the thread has gone, whip the head off and have it helicoiled, job done..

Didnt have to have any machining done on the B40 to fit PVL. However it's a points on the side cover engine and if i remember rightly the C15T should be distributor so might be a different system. Still looking at Mr Whittons C15T he's just blanked off the distributor and fitted a PVL in place of the Lucas alternator.

Agree it makes all the difference. First or second kick starting every time. Well worth the expense.

Thanks for the help guys, yes first thing I have done is fit a PVL from Sammy Miller, straight bolt on, although as ever the instructions were pretty obscure, new Mk1 Concentric going on this weekend and a flush of the oil system and we will see how it runs. I suspected a helicoil was needed, what is strange tho' is that the Champion that came with it fits fine! I will be competing on it so some bouncy rear suspension will be next, but I think this will also need a cub rear subframe as the seat height will be beyond my little legs.

There is a slight difference between a Champion and an NGK thread.

Most noticeable when the thread in the head is a little worn.

If the Champ works, go with it.

Autolite are good, too.