classic motorcycle forum

Hi,

The mixture seems way too rich and no matter what I do it does not lean out.

Have you checked the float heights?
Until you get the mixture correct the bike not much point in looking elsewhere

John

Hi Terrot
If the engine has wetted that Champion  it will be practically useless
In my misspent youth when all I could get my hands on were 2 smokes, you dare not venture far without a fistful of sparkplugs and a plug spanner
That was in the day when plug insulators were glazed and so cleanable  not like the shite available nowadays
A dodge to try that helps keep the plug dry is to fit an even shorter threaded plug from a chainsaw or strimmer / hedge cutter
Yes fit the exhaust pipe too
a bundle of NOS Champions here (3/8 reach)
https://www.ebay.co.uk/itm/vintage-champion-spark-plugs/123988529623?hash=item1cde4ad1d7:g:9UwAAOSwkARd3Bq7

John

Hi
One on fleabay

https://www.ebay.co.uk/itm/Vintage-BSA-C15-B40-drivers-footrest-40-4805-one-only/223764006368?hash=item34195fc5e0:g:vYUAAOSwfCRd2bgJ

John

Hi John,
A pilot jet must be fitted either the bush or a screw in one shown in this rebuild guide
http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter

John

Hi'
I still believe the fuel level is too high, maybe 2mm below venturi would be nearer the ideal
Does the carb have a pilot circuit? I cannot remember and I.m not going to re read all the pages 
In more modern carbs the needle virtually closes off the fuel at low throttle positions and the mixture is provided by the pilot circuit,

I started with 2mm dia and it is now closer to 3mm.
The needle is 2.4mm Dia.

If that was the case the throttle slide and needle would not close to the bottom
If the thickest part of the needle is 2.4mm I would guess the needle jet should be about 2.5mm

John

Hi John1168,

Are we saying that the addition of some screwed dowels  into the base of our Ariel Mag might make it fit ?

Not might it will fit

Some mags I have removed from BSA's had screw in dowels in place, rather than the more common pressed or cast in ones
I have both Ariels and BSA's and worked on more mags and bikes than I care to remember
Ariel's use a third bolt that goes into the fifth hole in the centre of the "four in a square" on more usually found mags
So if fitting a "normal" mag to an Ariel the extra hole will need to be drilled and tapped

John

Hi,

I would prefer a prewar but new ones are possible too.  Looks like the style I like dies out around mid 50's.

I would recommend buying a bike from a major producer, BSA, Triumph and the like where there are better spares available, although some parts of "common" popular bikes are scarce
WD bikes seem overpriced to me and prewar bikes command a premium
Buy a bike and see how you get on with it, you can always sell it on and buy another
Its easier to find bikes once you are out and about riding one.

I like BSA's for several reasons,(some sentimental as my first real bike was a BSA)
parts remained common (enough) to transplant across lots of years

A BSA B31 from 46 to 50 would fit your requirements and your budget ?
The 46/47 ones have a different gearbox to the later and bits for the early boxes are scarce
The one Andy has for sale has something "funny" going on with the rear guard on it, which maybe a bargaining point

John

Hi All,

Can valve timing be known to move on these.

Not unless something jammed the timing gears and sheared the key in the crank pinion
Remove the tappet cover, wind the engine to TDC, if both tappets are free (the pushrods should be free to rotate at TDC on compression stroke) then turn the crank one more complete turn
As the piston rocks over TDC you should be able to see the exhaust tappet dropping and inlet rising this should happen equal amounts either side of TDC

I now see you have a a concentric, The pilot passage bush within the body gets blocked,  a 16 thou guitar string or a no. 78 drill can be used to poke through the pressed in pilot bush
It has happened that new concentrics are not set up properly or have swarf and so on inside

John