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I think I have the std 18/40 sprockets on and am thinking what would be more suitable for Classic use on the back roads. It would make more sense to put on a smaller box sprocket as it would be cheaper than the rear and just involve a little chain shortenning. What do you think?.

Front sprockets usually are more expensive than rears, as they are splined and hardened.
There's not a huge amount in it though, so you could decide with other considerations.

Hi Jordan, I'm more interested in what drop in gearing to go for .the current set up is really high ,a bit like a modern car which has a 6 speed box with an overdrive top that never gets to rev. From memory to achieve max revs in 5th I would be doing 115 mph. Not likely now or ever ,although I did manage 104 half a century ago !!. ( I think it got to 8350 in 5th) leaving a Norton 500 88SS well behind.

Aye Bob,

Hooligan!

Dropping tooth size on the front makes it tighter for the chain, so more wear on chain and sprocket! But, this is for pootling, not racing a Norton 500 88SS out to Box Hill and back!?!

Drop her a tooth at the front and see how it goes. If I remember correctly, dropping one tooth at the front is similar to going up two teeth on the rear and I have no idea what ratio front:rear you have at present. On the 450, I think I am about 2.6:1 final drive, with a 16 tooth front sprocket and a 42 tooth rear(?), but I cannot remember the latter off-hand. Good for 55mph gentle riding down A, B, C and Unclassified roads up here and will pick up the skirts if needs be!

Good health and avoid that lightning! Bill

I'm running 18/47 on my 250, which it pulls with ease; next time I may go 18/45.

Colin

18/40 gives me a 2.222 final drive.Just stupid !! A smaller front will also mean I can use the existing chain , Also planning what to do about the ported 40 mm valve head and revvy cam. A swap with a 36 mm valve Dianna head and 27 instead of 29 mm carb would be ideal. Alternatively a swap with a tasty 200 elite bike would also make sense. And some clip on swan neck bars !.

Bob

I always recommend 17/45 as an average gearing which is Monza gearing. However it is so difficult to be precise as people ride differently and frankly weigh and different aerodynamic profiles play a large part in gearing Mach 1 gearing was probably aimed at sub 7 stone short stick like Italian youngsters not .......I'll leave it there!

On the basis that most race bikes would struggle to pull 18/40 I think a road bike would need to be falling off a cliff to take advantage!

Regards Nigel

Now I have got my 250 back in action ,I must change the gearing .Sadly Nigel is probably right, Monza gearing most suitable for old fossil , Don't think I can take his other recomendation, cliffs are too difficult to access and my brakes are not suitable. Trying to keep the 40 rear and just shorten the chain so looking for a 16 front , anyone got a scrolled one to swap with my good 18 ?. Two even numbers wear badly ? a 17 will give me 2.35 which is still a bit high. Birthday soon so a word in sons ear may get Nigel an order.