G80CS Gearing

[TOK]

Has anyone changed the sprockets or transmission to get better "road" use of a G80CS?

thanks
Tim

[AFJ]

G80CS gearing

The 1956-on Matchless G80CS (or AJS18CS) usually came with a 19 tooth engine sprocket but can be fitted with anything from 16 tooth to 22 tooth (22 is the normal road riding gearing.)

With a 22 tooth engine sprocket you get a 5:1 top gear ratio which will mean 6,200 rpm will give about 95 mph. Cruising at 70 mph is around 4,500 rpm.

AFJ

[TOK]

AFJ,

Thanks.
Usability wise...
The higher the engine sprocket teeth the better top end, what does that mean low/ mid range use?

I'm almost sure I have an 18 tooth sprocket...
Thoughts ??

Thanks for your advice.

TOK

[AFJ]

It depends a bit on whether you have the road ratio gearbox or the wide ratio trials gearbox.

Looking at my notes from over 30 years ago when I had a 1957 AJS 18CS with the short stroke alloy engine, I can figure out the following. (It had a 4.00 x 18 rear tire and I had 16, 19 and 22 tooth engine sprockets on it at various times.)

If you have an 18 tooth engine sprocket and the standard ratio gearbox you will have top speeds in the gears of about 25, 45, 55 and 75 mph, with the wide ratio gearbox it will be 20, 30, 50 and 75 mph.

With a 22 tooth sprocket and the standard ratio box, 35, 52, 70 and 95 mph. With 22 tooth and the wide ratio box, 35, 40, 65 and 95 mph.

The alloy short stroke AMC motor has plenty of torque to pull 22 teeth on the engine sprocket and this gives about 70 mph at a relaxed 4500 rpm. redline being 6200.

AFJ

[TOK]

AFJ,

Thanks for the additional info and keeping your notes! That is inspiring.
For what it's worth the bike is a 1961 (G80CS) long stroke alloy engine.
I believe the sprocket are standard, and the transmission is the wide ratio. I will check and expect that I'll be going up to the 22 tooth engine sprocket as I progress.

thanks again.

Tim OK

[AFJ]

You're welcome.



AFJ

[TOK]

AFJ

Very cool pict.
I assume that the Triumph is yours? ...AFJohnson?

FYI The Matchless is originally from the Flint Michigan area. It was raced, could have seen a Jack Pine in it's day...

I'll (try to) load a picture of the G80CS and me on our last big ride ( with the Viking Chapter gang), about 1,500 miles round trip to the Sturgis rally in 1999...

cheers
tim

[AFJ]

Yes, I'm on the 1927 Levis 250 cc 2 stroke and the 67 Triumph T100C Trophy "Jack Pine" is in the background. Picture taken at this year's Allegheny Mountain National Road Run where the freshly (home) rebuilt Triumph did the 350 miles without missing a beat.

A better picture of the Triumph in '04 at the end of a charity trail ride to support the Canadian ISDE effort.



Will try to Private message a picture of my 18CS.

AFJ

[JohnR]

In 61 I had a G 80 CS

Tecate Mexico

[TOK]

Allan and John,

Thanks for posting the picts they are grrrrreat!
It's good to you bikes in places where they were used! That certainly motivates me to get my ol girl back in road ready trim...
On Sunday a friend helpd and we got the stuck rotor off nt bike. It seems to hve gotten loose and chewed up the key and then the inner hole got out of round... so it needs to be replaced. The crank shaft looks good and so does the altenator.
Thanks again....
I'll look for more pictures and keep you posted..

Tim Ok

[TOK]

Allan and John,

Thanks for posting the picts they are grrrrreat!
It's good to see your bikes in places where they were used! That certainly motivates me to get my ol girl back in road ready trim...
On Sunday a friend helpd and we got the stuck rotor off my bike. It seems to have gotten loose and chewed up the woodruf key and then the inner hole got out of round... so the rotor needs to be replaced. The crank shaft looks good and so does the altenator.
Thanks again....
I'll look for more pictures of the matchie and keep you posted..

Tim Ok

[JohnR]

Heres another Pic of my G-80 and my buds Bonny also in Mexico.

Long long ago and far far away.

[TOK]

John R,

Thanks for the picture...Looks like a blast,
A ride to Mexico sounds great....

Tim