BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: chaz on 04 Dec, 2021, 13:14

Title: B40 camwheel timing question
Post by: chaz on 04 Dec, 2021, 13:14
side points B40 1965, reading Ruperts book it says if there is a line and a vee use the vee to align .
my cam has a dot and an M and a 1 then opposite 180 degrees there is another dot.
hopefully the picture will show, as the bike wouldnt fire before I took the gear and clutch back out which mark do I align? thanks
Title: Re: B40 camwheel timing question
Post by: Derek996 on 04 Dec, 2021, 15:16
I haven't seen inside a B40 engine for about 40 years but that dot at the top should line up with a line or a dot on the crank pinion. I can see no mark on the crank pinion so presume it is out of sight at the bottom. Get the dot lined up with the mark on the crank pinion and I'm sure it will be fine.
Title: Re: B40 camwheel timing question
Post by: chaz on 04 Dec, 2021, 16:33
another picture, the small gear has the punch mark near the tab and the larger wheel has one by the M1 and the other at the top.
what does the M1 signify? Ive seen no mention so far
Title: Re: B40 camwheel timing question
Post by: Derek996 on 05 Dec, 2021, 11:58
No idea what the other marks mean but I think the dot currently at the top of your picture should line up with the dot on the crank pinion. I hope you haven't bent a valve.
Title: Re: B40 camwheel timing question
Post by: chaz on 05 Dec, 2021, 16:27
thanks Derek.
as it hasnt started yet , I think the valves should be ok. have re checked and cam dot islined upwith single dot already.

as I said, Rupert says a vee and a line, as the bike is an ex American flat tracker, maybe its a different profile, this backed up with the brazed A&R cam...
who knows.
Title: Re: B40 camwheel timing question
Post by: ducati2242 on 06 Dec, 2021, 13:03
Those punch marks dont look right . To far away from the tooth . Is that a further mark near  the punch mark at the top four teeth anticlockwise . If not put your piston at tdc  and make sure both valves are totally closed this will be tdc on compression stroke . The mark should only be a few teeth from from the crank dot . line them up and you will be near . I always use a degree wheel to line up valve timing and take no notice of any 50 year old dots .