I've finally got my 1948 ZB32 Competion running the way I wanted it. When I bought it was disguised as B31 so It got changed to what it should look like. It had the standard B31 cams and couldn't pull the skin off a rice pudding, as the saying goes. I discovered it had a 9:1 piston so it should have gone a bit better than it did. Then I found it had a 19t engine sprocket, it was geared as 500cc B33. No much wonder it had nae wheech! (Scottish term) I changed the sprocket to a 17t.
Then I got a very corroded alloy barrel and head which took me a while to get the rusted rockers free and a lot longer to get valves and a piston. Last year I got another 9:1 piston for the alloy barrel at +0.5mm oversize and duly had it bored to suit. I ran it last year with the alloy barrel and head and a pair of Clubman's cams (65-1346 inlet and 65-2446 exh with the 10º advance crank pinion) but the result was disappointing. The BSA lightweight gear box with its wide ratios didn't help. On hills it was either revving uncomfortably in 2nd or labouring in 3rd which brought it off the cam and it would misfire badly with anything wider than a small throttle opening. This weekend I changed the cams for a set of scrambles cams (65-2454 inlet and 65 2450 exh still with the 10º advance crank pinion). What a difference! It's now running cleanly under load and accelerating like it has never done before. I might try it with an 18t engine sprocket next year.
And a few more photos20230311_153437 copy.jpeg_IMG8688 copy.jpeg20230209_145309.jpg
Lovely looking bike. Glad you've got it running more how you want it.
Confess I think of the 2450 as a DB onwards exhaust touring cam but I see its use in most applications and the 2454 inlet for scrambles.
I've got 2448 In and 2450 Ex on my ZB34 Clubmans head bike - quite tractable with only 7.5:1 piston, but quite sensitive to exhaust type (Does not like the Burgess type silencer but the mini goldie from armours is better (louder so must be faster!!)
I've got a pair of cams here to try - a 2438 inlet and 2434 exhaust which were said to be for scrambles, grass track and sand racing (probably open pipe) but I do have a properly refurbished 1 3/16" 10TT9 for when I'm feeling brave.
The cams can make a huge difference to these bikes. Many years ago I had a DBD34 Clubmans and I also had a DB34 Tourer that I had bought previously. At that time, mid '70's, I bought every spare part I could lay my hands on. When I eventually had the Tourer fully restored albeit with the 2448/2450 but a 9:1 piston. I tried swapping the 2448 inlet for a 2446, Clubmans exhaust but also a Scrambles inlet. Wow! What a difference. A huge improvement in the bottom and mid range. It's not a cam combination that I've seen for any Gold Star but it worked for me. I tried that 2446/2450 combination in the ZB350 but it just didn't seem to work as well as I'd expected maybe with the 65-696 10º advance crank pinion it would have been better but I didn't have one at the time.
Your 2438 and 2434 cams were for a ZB engine intended for Scrambling. They don't have quietening ramps and clearances of .001" inlet and .003" exhaust are recommended.
I have those cams in mine, so maybe that explains the rattles.
Goes well though.