BSA C15 "Dizzy" upgrade to side points "F" type conversion.


If you have an Old Distributor type C15 or B40 engine and would like to convert it to a later "F" type specification?            Why would you want to??


Well for one thing you can fit later gears, have a better kick-start, and clutch mechanism.

And if you use points you have a better set up with more accurate timing.

Not that this matters if you are running PVL or Electrex ignition systems.


So what do I need?

The main things are a later inner and outer timing cover, side points camshaft, and as I have said a later set of gears and shafts including the kick-start mechanism.

You can use the original gears if you can find a "F" type main-shaft, and will need timing side layshaft gear.No 40-3260,3295 or for wide ratio3299.

These are not that easy to find, and I have machined up a thick spacer washer with bush fitted to fit inside the original Kick-start ratchet gear in the past , when I could not find an original.


 Here are some pictures with the difference with side covers ETC.



This is the original "F" Type inner timing cover with clearance for the engine main-shaft nut,Above.

The one below is a later end fed case that the seal holder as been machined off to give the same clearance as the case above. 



 The camshaft below with gear is the "F" type  to fit  the 9/16" smaller  inner bush.

The other cam is the original Distributor model cam that fits the bigger bush.





You can use the later type cam fitted to B25's, but these need the "Big Foot" cam followers,

and need the case welded up and machined with a surface these followers can run on, or a large bush with a lip machined into the case has a thrust surface.


Right, What you will have to do to fit the camshaft into the Ceefer, crankcase's, is to turn up a one off bronze  bush that will fit the 9/16" camshaft and fit the larger hole in the crankcase.


Here you can see the diffrence in size from the original "F"type bush along side. and the new larger one sitting on the camshaft.


Other things you will have to do to the crankcase for this conversion, is to drill the threaded gearbox gear-change anchor spring pin hole out to take the plane spigot of the "F" type anchor pin.



And also  drill and tap the  small hole, and insert a tapered grub screw (If not there) to

tighten in the machined  groove on the oil pump -distributor drive shaft bush to stop the shaft lifting.


The Blue arrow shows where you need to make sure there is a grub screw present? if not drill and tap a hole to take one.

The drill bit is in the hole you need to take the threads out of


Also don't forget when you fit the New one off bigger bush for the camshaft, you need to drill the oil hole from the crankcases through the bush top surface for its oil supply.

"This is most important."



OK, the gear on the left is the gear 40-3299 (Wide) that is specific to the "F" type gearbox.

If you can-not find one of these, you can improvise , and make up the gear on the right?


This is the kick-start gear from the Dizzie engine, and a bushed spacer that I have made up!

The inner bushed spigot of the gear needs machining down until ,with the spacer fitted it is the same height as the gear next door.

The spacer now needs tack brazing  into position, and the holes for the gear spigots in the rear of the gear spacer drilled to allow the selection depth of the mating gear enough movement for selection.



You will also need to machine up an alloy bung to close off the hole from the distributor drive.



This is the alloy Bung you need to knock up, to close off the distributor drive hole.

You could add a breather pipe to this outlet? but I tend to use a breather higher up on the  push-rod inspection plate.


A really good guide to this conversion is the "Rupert Ratio Unit Singles Manual"

This covers the bits I have probably missed out explaining.

I will update this page when I build the "Dizzy"engine up later.





OK.has if I had not got enough to do, with the builds I have. ?

But after doing this page just for the information!!


I am now building this engine up to fit into the SQ frame.

 I have a crank assembly on the way, barrel, cylinder head ,and all parts to make the engine into a "F"type.

I just fancy fitting an inexpensive clutch onto this bike ,but I am still doing the homework at the moment?Just going to make a five plate up from the parts I have.


Well this bike seems to want to throw its self together does it not.

The frame was only an experiment, but then got to good to waste.

I have some experimental Triumph / BSA four stud forks that are going on, Yamaha TY front wheel,

and yokes. What this bike will become is a typical British "Britshock" machine. or "Otter" of the future?

I thought it best to now build this engine into as good has it gets "Dizzy" engine.


So now have a timing side bearing conversion  from the "Good Guy's" at Dudley, Alpha Bearings,to fit , along with the steel competition crankshaft assembly.




I also have a superior oil pump in the throws of manufacture, and may fit this to the engine.




This engine is about to be fitted to the bike at last. it has been little things that have just not turned up on the auction site like they used to.

The Moto is don't throw anything away any-more because someone will need it,

So has I always say more later and pictures of the engine assembly.