Atlas engine and gearbox sprockets

jms

jms

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On an Atlas was wondering what people prefer for around town and back country roads relative to sprocket sizes. Here's what are with came with my project
1. Engine 19 teeth
2. Gearbox 19 teeth
3. Clutch 42 teeth
4. Rear wheel 42 teeth

Thanks
 
From the Norton owners club:

Highest speeds on standard gearing under favourable conditions,
(but not sustainable)​
Engine
Sprocket​
Gearbox
Sprocket​
Model​
Speed​
Rear
Tyre​
21​
19​
Norton Atlas110 mph @ 6400 rpm (M)18 x 4.00
19 x 3.50
21​
17​
N.15 C.S. and G.15 C.S.100 mph @ 6400 rpm (M)18 x 4.00
22​
17​
G.15 Mk.ll104 mph @ 6400 rpm (M)18 x 4.00
22​
19​
G.15 C.S.R.115 mph @ 6600 rpm (M)
116 mph @ 6400 rpm (M)		18 x 3.50
19 x 3.50
22​
19​
G.15 C.S.R. (U.S.A.)106 mph @ 6000 rpm (C)19 x 3.50
21​
19​
P.11105 mph @ 6200 rpm (C)18 x 4.00
M = magneto/Monoblocs C = coils/Concentrics​
 
The above would suggest your engine sprocket is too small. I am running a 21/19 on my G15 and find it a decent compromise- the bike can run smoothly at road speeds of 60-75 and still have enough grunt for good acceleration. My rear wheel is the same as your Atlas so the overall should match- clutch and wheel sizes are 42 on all.
 
I went up one tooth on my engine sprocket from stock ..... IIRC, i am now 22 vs 21.All else stock Atlas.

The vibes are comfortable at 3500 rpm, but become uncomfortable over 4000 rpm.

According to calculations, with 21 tooth engine sprocket, I got 17.5 mph per 1000 rpm, with 22 tooth engine sprocket, I now get 18.33 mph per 1000 rpm.
This translates to the following road speeds at the critical rpm's:

Sprocket. RPM. Mph
21T. 3500. 61
21T. 4000 70
22T. 3500 64
22T. 4000 73

Loss of acceleration is insignificant...... cruise comfort over rules winning stop light drag races.
 
Elfix said:
The above would suggest your engine sprocket is too small. I am running a 21/19 on my G15 and find it a decent compromise- the bike can run smoothly at road speeds of 60-75 and still have enough grunt for good acceleration. My rear wheel is the same as your Atlas so the overall should match- clutch and wheel sizes are 42 on all.
Click to expand...
Thanks
 
texasSlick said:
I went up one tooth on my engine sprocket from stock ..... IIRC, i am now 22 vs 21.All else stock Atlas.

The vibes are comfortable at 3500 rpm, but become uncomfortable over 4000 rpm.

According to calculations, with 21 tooth engine sprocket, I got 17.5 mph per 1000 rpm, with 22 tooth engine sprocket, I now get 18.33 mph per 1000 rpm.
This translates to the following road speeds at the critical rpm's:

Sprocket. RPM. Mph
21T. 3500. 61
21T. 4000 70
22T. 3500 64
22T. 4000 73

Loss of acceleration is insignificant...... cruise comfort over rules winning stop light drag races.
Click to expand...
Thanks
 

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