Hi all me again! Yet more advice needed re cylinder head on my 67 hornet. Just about to fit new guides etc and i noticed the new Hepolite springs ( to fit 66 on ) do not sit within the spring cups believed to be original.Does anyone know if there was a change in the above at any time,and could i machine the cups to accommodate the larger diameter of the new springs. They measure 1.2865 on average and cups 1.2530 or thereabouts. Sorry if i appear a little green on these matters but thats because i am!! Thanks guys. Dave
I had the same problem with my Royal Star. The new springs were just too big for the bottom cups. One of the cups was slightly larger so there were definitely two types. My take is that maybe the springs were strengthened (so larger) and there should be later cups to suit. However, as is often the case parts get mixed up in our sheds etc.
I ground a bit of the bottom coils to enable a snug fit. Not much loss of metal, so no sleepless nights!
Chris
Hi,
Over the years there were 3 different bottom cups, 2 different top cups, 3 different inner springs and 5 different outer springs.
A lot of sales companies state from 1966 on, but its too generic for my liking. If it don't fit its wrong, springs have different spring loading, thicker dia coils, more coils etc. Your best bet is to contact SRM in wales who will probably get the correct or nearest for your bike.
This article is worth a read before you make a decision:
https://www.classicbritishspares.com/blogs/news/replacement-bsa-a50-a65-valve-springs-1962-1972
Best wishes...
dont forget the different sized cotters as well