Posts
21449
Joined
8/15/2006
Location
AZ
US
Edited Date/Time
1/2/2021 8:02am
explain why the rotary valve two stroke isn't used by anybody still making them? Is there a rule or patent that prevents this from happening? Back in the day the Can Am's and the Puch were the fastest scooters around.
Look at all that travel
He had the "Skunk Intake" mod done up by Dallas Baker. It was fast but not very reliable, as I recall.
The Shop
Positives: Better low end torque and quicker engine response.
Negatives: Heavier, more moving parts, wider engine, and more difficulty moving air at higher RPM (but Can-Am seemed to figure this out).
If you're asking for an intelligent answer, why not compose your post better than an average 8th grader?
Think i saw one at Msvl 10th Street ... beautiful bike .... Charlie Sexton came by and smacked me on the back of my head for not watching the track ... i was finish flagging that day .... ; )
Disc valve engines can have much more focused inlet timings than Reed / piston port engines. Generally, with the last of the modern era Road Race 2t engines, the Reed Valved engines, tended to produce more low / mid range, as against the Disc Valves propensity for top end. Look to the Hondas Vs the Aprilia is 250s for that 'battle' of concepts. That, of course, Honda largely gave up on - but they did make damned sure they "back doored" enough tech for a Honda to get the last ever 250GP World Championships - the cynical effing pricks.......
There's a very clever Kiwi (they're a horrible mob, but even better than Aussies when it comes to the ability to make a Space Shuttle from barbed wire and some 2 x 4s) on Twostrokemotocross,com that's been making a Disc valve 360, and another engine, if you want to see what a clever / determined bloke can do. There are a couple of blokes there that champion the Disc Valve above all other induction systems, but, I take their points with a grain of salt - 'enthusiasts' for at type of tech, can be very one track minded.
The last years of the Aprilia 125 GPs bikes was a Disc valved engine ( well, they were for a very long time, as were their 250 twins), with a Big Difference in that the disc was mounted at the rear / top of the cases. Yet, with the 500s 4cylinder 2T GP bikes, they had all long gone to Reed Valve engines. Perhaps it came down to simply not needing such power potential???????????
Even CZ had that type of engine - disc valve geared onto the back / top of the cases - in their last years of 125 experimentation (as well as a Twin Cylinder MXer):
Just for kicks - The CZ125 twin - but with conventional Reed Valve:
More top end, is not the absolute be all and end all, especially on the Dirt. Even on small capacity bikes. Some Disc Valve engines used a reed valve component to them, to 'fill out' the power delivery (I think the Kiwi I mentioned is using that set up as well). Who knows what we would have had if 2ts hadn't been usurped by 4ts in factories interest? There's an enormous amount to come from 2t development, just as there is an enormous amount to come from 4t development. Look to the Moto3 class for what may come for single cylinder 4ts, without outragious rev limits ( they've been limited to 14k revs, and are / have dropped to 13.5, and perhaps will go down to 13K under the rules). So, we may end up with mid 50 HP 250 4ts, that don't have to rev to the moon as they do now - re Bike It Yamahas/ Cosworths 16.500 RPM / mid 50 HP 2013 MX2 bike - , don't need this omgoing BS of 'handicapping' rules. Equivalency racing, is how it should be - it makes for great racing, with great sounds coming from both types of engines.
Pit Row
The section on disc-valve states this:
...
However, it was not long before it was learned how to produce equal, if not superior, performance from piston control of the intake system. The current technical position is that the reed valve has supplemented the piston-controlled intake port for racing engines and is probably the most popular intake control method for all engines from the cheapest 2 hp brushcutter to the most expensive 300 HP V8 outboard motor.
...
So there you have it: You can equal or surpass the disc valve with a cheaper/simpler solution.
URL=http://s223.photobucket.com/user/WandellAsbell/media/SXcomGlover/SXcomY…
You should ban yerself for a few days... You could use a vacation brother.
already plenty of power, there's no guarantee that a RV engine would have more power now
no r&d pushing the 2 st envelope, (even KTM although moving forward are not under any pressure so move very slowly)
1) extremely inefficient, lots of wasted fuel
2) extremely emissions unfriendly, lots of unburned hydrocarbons going out exhaust
3) high wear on moving parts, particularly when oil injection is not used. Most rotary valve mechanisms use oil from the injection tank to recirculate oil to provide sump type lubrication for rotary valve. Lots of problems associated with that.
2. reed valves are much cheaper to design
3. reed valves are much cheaper to manufacture
4. reed valves require very little maintenance (almost zero maintenance if metal reeds are utilized)
5. reed valves are not related to port timing in any way, allowing for easier tuning and a broader tuning range, which generally translates into a broader, more usable spread of power.
obviously there are reasons...
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