Ajs model 20 gearing

[Manky55]

Hi all I have a 1952 Ajs model 20 Which seems to be reving high in 4th gear could someone tell what number of teeth is standard on the primary gearbox and rear wheel please.

[Groily]

See http://archives.jampot.dk/book/Spares_l ... s_List.pdf
Which lists sprocket options on crank of 19/20/21, 40 clutch chainwheel, 16 on gearbox and 42 rear.
Many of us use 17 on gearbox for a bit more length. Think I am 20-40-17-42 and it's OK. (Edit - Up to about 60mph)
Sure the clutch isn't slipping?
Happy Christmas!

[Manky55]

Thanks for the info on inspection I’ve found I have 18T primary 40T clutch 16T gearbox and 42T rear wheel, this explains the high revving, the next problem is where to find 20T / 21T primary and 17T gearbox sprockets any ideas anyone please.

[dave16mct]

Club spares have the 20T engine sprocket. I'd hold back on changing the gearbox sprocket until you've given that a try.
Dave.

[Groily]

I agree. Lot of work to change the 'box sprocket if you can get a straight 2 tooth increase on the crank and find you're happy enough at that. Might have to check primary chain length though, to see if there's enough adjustment on both chains to allow the change.

[Manky55]

Club spares have the 20T engine sprocket. I'd hold back on changing the gearbox sprocket until you've given that a try.
Dave.

Cheers I’ll take a look

[frankjames]

Hi Manky -

I've been contemplating making the change to 20T on engine to make the long straights a bit less "jangly". Curious to hear whether you made the change to 20T and if the result is satisfactory? Thanks.

[Trefor]

I sort advice from this forum over gearing on a G9 and was recommended 20 crankshaft (standard) and 17 gearbox (one more tooth than standard) for more relaxed top gear running. I used this combination and find it works well for me at 50-60mph. The alternative is to fit 21 at the crank (factory alternative) with 16 on the gearbox. I gave up on this because I couldn't easily find a 21 sprocket. Using this calculator on a web site, 20-17 gives a very close to the 21-16.
http://www.nightrider.com/biketech/calc_gearratios.htm
You need a half link to accommodate the 17 tooth sprocket