Singles with different characteristics

[EddieDay]

Now that I ridden a couple of hundred miles on my M18S I have been thinking about how different the bike is to my Honda FMX 650. Some of it is obvious given that one is 47 years older than the other, e.g. the Honda has disc brakes, hydraulics, big upside down forks and an electric start. But the engine characteristics are very different. The AJ will happily chunter along at 25mph in top. The Honda needs to be in second (out of 5) at that speed. Blip the throttle and the Honda rasps immediately to high revs. The AJ sought of says "well OK then.....I will speed up".
Of course once you compare the engines you can see why this is so. Even thought we call the later singles "short stroke" they are still longer than square. The Honda by contrast has a bore of 10 cm and a stroke of 8.2 cm. I guess the flywheel of the Honda weighs about half that of the AJ and the Honda has 4 valves and twin exhaust ports. The FMX is quite detuned compared to the XR650 with only an 8.3 : 1 CR compared to 10 : 1 for the XR.
I am loving the unfussed way the AJS goes about its business though.

[EddieDay]

And maybe I should have mentioned:
M18S: Power - 25 - 28 bhp (depending on source), Torque - 24 ft.lb, Weight - 386 lbs.
FMX: Power - 37 bhp, Torque - 38.6 ft.lb, Weight - 350 lbs.

[billbeavis]

Is it the change of engine design to get more power makes for the different characteristics? How does riding a new 350 RE which produces 20 HP compare to riding a Matchless 350 producing 19 HP? I guess similar to your comparison as the RE revs higher. Also although the RE produces similar HP to the Matchless / AJS I know Lesley mentioned she rode her 350 RE at a steady 70 MPH on the way to Bishop Auckland. I was keeping to 50 / 55 MPH on my ride there for mechanical sympathy.
How about why do the twins produced by the different manufacturers over the years sound different to each other? It's easy to tell one of our twins compared to a Triumph for instance. Especially the one used on the opening of the Antiques Road Show. Bill

[jackstringer]

If you keep up with Ryan at Fortnine you will have heard him talk a few times about the ways that engine design especially in singles is rather interesting. Stroke, piston size, crank weight etc all have things that effect the engine.

Husaberg even tried rotating the barrel etc to change the way the bike rode. Using the up down to do more a push pull thing. I own a few bikes and most are Singles with the odd twin and one sewing machine sorry R6. They all ride differently and that is one if the best things about them.

[SPRIDDLER]

The AJ will happily chunter along at 25mph in top. The Honda needs to be in second (out of 5) at that speed.

The 40's and 50's AMC engines were designed primarily for ride-to-work reliability. Modern bikes are designed (to generalise) mainly for fun.

AMC pushrod 500cc - Bore 82.5mm x stroke 93mm (A long stroke heavy flywheels plonker).

Honda OHC 644cc - Bore 100mm x stroke 82mm. (Oversquare bore/stroke and sprightly).

I have a 1954 G3LS and a 2016 Chinese Herald 250 single which has a licensed copy of the Suzuki GN 250 engine and am rarely tempted to ride the characterless Chinese bike which never needs any TLC.

G3LS 348cc pushrod 16 hp @ 5200rpm - Bore 69mm x stroke 93mm. (A long stroke heavy flywheels plonker).

Chinese 250 Herald OHC 22 hp @ 8500 rpm - Bore 72mm. x stroke 61mm. (Oversquare bore/stroke and sprightly with constant tedious gear changing to keep the revs up).

If it wasn't for busy roundabouts and traffic lights I could ride the Matchless in top gear from home to the Pyrenees.

[EddieDay]

"If it wasn't for busy roundabouts and traffic lights I could ride the Matchless in top gear from home to the Pyrenees."

Spriddler, I am sure that is right. This morning I rode up Box Hill on the zig-zag road in top gear at 30mph - apart from the hairpin bends! I am still being surprised at the capability of the old girl, especially at slow speeds. I can see why the comp models were such good trials machines.