Gas Gas side valve.

[Motu]

If you wait long enough they will reinvent the wheel.10,500rpm - wow,this bike impresses me.

[slowpoke]

I wouldn't have believed it if I hadn't seen it, thanks Motu.
I guess if you are chasing compact dimensions (as on a trials bike) rather than outright horsepower it makes sense.

[Motu]

Torque - all the best motors in the world make torque,not horsepower.Torque comes before the horse.

[Ocean1]

Cute, very cute.

And tiny, what's the capacity Motu?

[pete376403]

And motors that should be sidevalve - lawnmowers - are now getting overheads.

[F5 Dave]

Torque - all the best motors in the world make torque,not horsepower.Torque comes before the horse.

Pity the damn greenies have so much pressure these days. Trials engines would have stayed 2 stroke, because of course they can produce more Torque.

yup.

No need for 10500rpm

[Motu]

Yeah,it's funny how misinformation is considered gospel truth.Everyone thinks a long stroke 4 stroke produces a lot of torque...well it does,but not very useful torque.The absolute stump pulling,front wheel lifting torque from idle that a trials bike needs is best made with a radically over square engine with a short rod.A short,sharp....Think hydraulics or pneumatics.You wouldn't think 10,000rpm would be needed - but when you see these guys wind the engine up then launch at a 3 metre high vertical wall from a standing start with no run up you see why.

[F5 Dave]

. . . but when you see these guys wind the engine up then launch at a 3 metre high vertical wall from a standing start with no run up you see why.

Yeah, but they're brain-dead, or young or something.

[Ocean1]

Yeah, but they're brain-dead, or young or something.

Synapticly challenged mebe, but most of your local regulars are fooking ancient, and still defying gravity tolerably well...

[F5 Dave]

Yeah but I don't think even Lawton would try & convince anyone he was the full quid. Some of the others seem to have a similar lack of understanding of what is & isn't possible. Like the bumble bee theory I'm sure. They don't know its not possible so they do it.

Trials seems like such a slow & boring sport until you are balancing looking up or down at something that you just don't want to attempt but people are watching.

[K slider]

Yeah but I don't think even Lawton would try & convince anyone he was the full quid. Some of the others seem to have a similar lack of understanding of what is & isn't possible. Like the bumble bee theory I'm sure. They don't know its not possible so they do it.

Trials seems like such a slow & boring sport until you are balancing looking up or down at something that you just don't want to attempt but people are watching.

We might not be the full quid but after 32 years on all sorts of bikes those seatless skinny beasts still give me a thrill that cant be equaled, although my worst and life long injury came from a 260 Beta I still cant resist an offer of a ride on one.
You need revs when you attempt a long technical climb where the start has to be fast but midway have to go slow. My stroker sounds like a chainsaw sometimes.
Cheers Pete

[koba]

Cool shit! being in my twenties I have rarley delt with side valves an any way.
I was amazed when I got to ride a BSA M20 (600 Sidevalve single, loooong stroke) It had no powerband at all, les revs made it go faster?!?! Strange...

[Motu]

M20 = 500cc,M21 = 600cc,same bore,the M21 had a longer stroke,both longer than the B series.I had an M20 for years,in a '54 A10 frame.They used the same cams as the other B series singles,opperated about 1,000 rpm lower everywhere.Kinda like a diesel for power and torque - catching a wiff of a hill speed would start dropping off very quickly,but once down to 35mph in top gear that was it,it would go no slower,no matter what the grade or the load it carried,just got down to it and battled away.

But I doubt this Gas Gas sidevalve opperates the same way - it sounds really blatty at low speeds.The Yanks were the best around in sidevalve tuning (Ford V8's,Hudsons,K Harley's on the dirt tracks),maybe some old hot rodders retired to Spain?

[quallman1234]

Talking about valves and stuff, didn't they use a 2 valve head at one stage on a two stroke back in the day of the 500cc 2 stroke racers/650cc like 20/30's era

[K slider]

Talking about valves and stuff, didn't they use a 2 valve head at one stage on a two stroke back in the day of the 500cc 2 stroke racers/650cc like 20/30's era

Dont know about valves but my old man raced an NSU with an extra piston in the crankcase that charged the cylinders, was later banned as it was regarded as super charging.
On the subject of trials 4 strokes Scorpa has put 5 valves in its Yamaha head.