Hoping someone can help me. I have a ZB33A competition engine with a plunger frame which was made in 1950. My question is what are the correct valve clearance and ignition timing BTDC figures for this engine? Since the engine has a factory fitted B34 all aluminium barrel and head do I set the valve clearances at the standard B33 setting, or do I set them for a Goldstar engine?
I am told this configuration was only produced by BSA from 1950-1951 does this make my machine a rare model?
Any help would be appreciated.
Graham
The valve clearances are shown as 3 thou both valves for B33 and the non Gold Star competition B34. Timing shown as 7/16 BTDC on advance for both.
Information from 1950 BSA Data book.
From 1955 ignition timing was changed to 3/8 inch BDTC on advance.
Valve clearence is dictated by what cams are fitted not the year of the bike
Hi Julien, Thanks for the most useful information. I was told that since the engine had factory fitted GS barrel, head, valves and 1 3/16 " 10tt9 carb, then the valve clearances and ignition data would be different to a standard iron barrelled B33. Many thanks Graham.
First photo shows the standard cams fitted to the Alloy barrel B33 B34. 65 2420 which is the same as the iron barrel cam.
Second shows the optional cams.
All above from the 1950 parts book.
Service sheet 707 gives valve clearances for Gold Star and comp models. See last photo.
The 8 and 10 thou clearances are for the ramp cams.
Julian,
You are a star! Thanks for sending me the information. I had set the tappets at .008 and .010 not knowing what cams had been fitted, but the engine sounds too tapperty, so .003 on both should quieten things down a bit. Many thanks Graham
Sounds like an interesting bike.
I think the last alloy ZB33 were exported in 1952.
Hi Julian
Thought you might be interested to see the bike.