MK2 up second gear different? How so?

I see that the gearbox second gear was changed in the MK2. I did find one reference in this site that said the later 2nd gear was taller.
Is this a noticeable difference? Would a casual rider be able to tell? Just curious.

Others smarter than me can give specific ratio but in practice on Combat its the Cat's Meow for a passing gear and allows down shift w/o chattering the tire of over winding the engine when getting frisky. I highly recommend it as useful practical pleasing upgrade by Norton. Holding onto Norton in taller second may become your most favorite thing to do, but alas the longer one stays in lower gearing especially nailing it the quicker the sleeve bushes disolve and clutch basket wobbles onset. In it was just this excessive pleasure seeking and getting ahead of others that just couldn't believe it, caused me to use Dextron ATF in my taller 2nd gear Peel. Put on 20 or 21 tooth sprocket and this 2nd is good to nearly the Ton!

rwalker28 said:

I see that the gearbox second gear was changed in the MK2. I did find one reference in this site that said the later 2nd gear was taller.

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The higher ratio 2nd gear was first introduced on the 850 Mk1A low noise emission model which was introduced in order to comply with new European noise emission legislation.

I believe the noise measurement testing had to be conducted with the machine ridden in 2nd gear, and to keep within the specified noise limit the factory increased the 2nd gear ratio as the reduction in RPM reduced the noise output.

Andover lists the high second gear as a replacement for the electric start MkIII only. The parts list for the 74' Commando lists it's second gear as "early", so maybe the high second was not put into hardly any 850s except for very late 74' and the E-starts?

beng said:

Andover lists the high second gear as a replacement for the electric start MkIII only. The parts list for the 74' Commando lists it's second gear as "early", so maybe the high second was not put into hardly any 850s except for very late 74' and the E-starts?

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You have to remember there were two separate versions of "Mk2" built during the same 1974 period. The standard Mk2, and low noise emission Mk2A.

Unfortunately the Andover Norton parts list for 1974 is misleading, as it doesn't list many of the parts that appear in the '74 Mk2/2A (307311-on) supplement which perhaps you do not have a copy of, and the low ratio 2nd gear pair isn't listed in the 2/2A supplement, only the high ratio pair (064639 & 064640). If you check the AN lists for 1971-72-73 it also says "18T (early)" for the 040418 mainshaft 2nd gear! AN's 1974 list is basically the 1973 list with a few alterations. I suppose one day AN may get around to sorting it out properly. :roll:

The same high ratio 2nd gear pair are also listed in the 1973 Mk1A supplement which I also guess you do not have a copy of? Therefore I think it is likely that the high ratio 2nd gear was fitted to all low noise emission 850 Mk1A and Mk2A models from late 1973 onwards and possibly the Mk2 as well, or at least sometime shortly after.

Thank you all for the replies. Good to know. My gearbox has the taller gears installed (with the grooves in the dogs - the parts manual I have calls for the older gears - that was my confusion.) The vin on mine is 30738X (Aug 73) so a very early 1974 model. The bike has 2200 mi on the clock, I got it as a pretty complete non-running bike, the gearbox looks original, but who knows.

I find that the Taller second gear works Much better for me in the Mountains! when I am lucky enough to be in them... 2nd was way too low most of the time while the MkIII gear becomes very useful. but that is just me, I have been mistaken before..