gearbox Sprocket 1956 Dommie 88

Changing the box sprocket is a lot of work , especially if you dont like it .  An extra tooth on the engine is a bit easier  as long as you can break the taper.   The 88 is a revvy engine  so you may find yourself running more in third  when in the 30 zone.  Even on the 99 i find myself looking for a 5th gear . and  changing down to 3rd a lot in traffic..  A 5 speed cluster with a lower 4th gear and an overdrive 5th  would make  a great improvement .

Are in stock in the spares department 20T and a worn 21 if you're determined.  My 88 was a slouch on the hills and I suspected PO had sprocketed  it to cut the revs out.  Turned out to be a mag issue.  That resolved, I then put a 20T in and it pulled it nicely (ONE UP though) and gave a great turn of speed.  I liked the flexibility of running in third when in urban limits,  but calmed it  down on the motorway stretches I can't avoid....

I have yet to take my Dommie racer 88 out on the road but in advance I can tell you that I have fitted a 20 T G / Box sprocket, leaving the engine sprocket as std.

This arrangement works very well on my 99. In fact I also use a 20 T G/Box sprocket on a couple of my singles inc my big bore ES2. (530 cc)

If you do decide to change the gearing, don't forget to re-adjust the rear chain.

PS: RGM have a wide range of G/ Box sprockets, certainly up to 22T.

https://www.rgmnorton.co.uk/buy/amc-gearbox-sprocket-20-teeth-5-8-x-1-4_1068.htm

I'm assuming an AMC box, but might be OK pre 1956