Aprillia 125 2 stroke disc valve

[feejer222]

I know its potentially extinct technology, but it's what I was involved with and is always nice to hear about it still being used.

The Aprillia's use rotary disc induction, which is basically a disc with a hole in it that spins on the end of the crankshaft. The disc is timed to open up a hole direct into the crankcase at the begining of the induction stroke, and close off the opening at the begining of the transfer stroke. This gives very controlable timing to the induction, better (IMO) than the usual piston skirt, or reed valve controled induction, on a convetionally aspirated 2 stroke.

The Aprillia's have come up with a design where the disc is controled by a gear and is turned through 90 degrees and is set at the back of the crankcases to give a more stable air flow and gives better engine cooling. The gear system kept breaking last year, but has been sorted now and I predict they will dominate this year.

We ran a Sanvenero 125 at international level for a year, there were only 2 in the country at the time, it was probably the most enjoyable bike I worked on and was incredibly fast.

The Kawasaki 250 & 350 of Kork Ballington back in the 1980's used rotary disc induction and I often wondered why no-one else tried the technology.

 

[Stephen]

My long course racing kart has a Rotax 122 in it, also a rotary valve engine. Faster than slick snot on slug juice! :dribble:

My kart (Zipkart chassis) is black without the wing. 136+ mph at Portland International. :yahoo:

 

[feejer222]

My long course racing kart has a Rotax 122 in it, also a rotary valve engine. Faster than slick snot on slug juice! :dribble:
My kart (Zipkart chassis) is black without the wing. 136+ mph at Portland International. :yahoo:

I forgot about the Rotax's. They were quick back in the 80's. A British company called Armstrong bought them and built a race bike around them. They had a lot of problems with siezures in the early days. Nial Mackenzie (Scottish 500GP rider in the 80's) had his first 'works' ride on one.

I am sure CCM still use them in their enduro bikes.

 

[charismaticmegafauna]

Rotax (Bombardier) used a disc, drive set a 90 degrees to the crank ('Priller-style), on 2-stroke twins back in the early '80s.

Of course, Yamaha used rotary disc valves on production motorcycles in the '60s.

And....there's even more history -- further back. :huh:

 

[feejer222]

Its surprising when you start digging how far back stuff goes.

A guy I worked with used to make his own reed valves back in the late 70's. He machined the mount and made the reeds himself believe it or not from finest irish linnen and a fibreglass concoction. Or at least thats what he told us, it was all top secret at the time.

He was 25 years older than me and had worked with reed valves in a commercial situation in the 1960's. He marketed his own brand of reed's over here and did well with them selling them as aftermarket parts to all the boy racers with 2 strokes. His name was Hargreaves and the product was called the HARPOWA reed system.

I still have his sticker on my tool box. He was a very clever guy and helped us a lot. We did track developement work for him using a 250 TZ engine of his in exchenge for his help. The last thing we tested for him was a trigger on the bars that had to be pulled at about 5000 rpm which lifted the reeds completely out of the way of the gas flow. He reckoned that they didn't function beyond those revs. It worked but he never marketed it. He went to Italy for a season and worked with Roberts on the Marlboro Yamaha's. Not seen or heard from him for years now.

 

[TestPilot]

The Kawasaki 250 & 350 of Kork Ballington back in the 1980's used rotary disc induction and I often wondered why no-one else tried the technology.

I met up with Kork a few years ago, here in Brisbane now. Always supported him from my days in South Africa, and in the early 70's did quite a bit of photography around race tracks, as well as working with a SA 250 champion for a few years (Kevin Hellyer, whose son Dane is making a name for himself in racing now). Spent some time at the GoKart track with Kork while I was still racing (Rotax motors). The organisers of an annual historic racing meet here are trying to convince Kork to put one of his championship bikes on the track later this year, or early next year. Maybe I'll have to contact him and see if he needs a spannerman.

 

[feejer222]

The Kawasaki 250 & 350 of Kork Ballington back in the 1980's used rotary disc induction and I often wondered why no-one else tried the technology.

I met up with Kork a few years ago, here in Brisbane now. Always supported him from my days in South Africa, and in the early 70's did quite a bit of photography around race tracks, as well as working with a SA 250 champion for a few years (Kevin Hellyer, whose son Dane is making a name for himself in racing now). Spent some time at the GoKart track with Kork while I was still racing (Rotax motors). The organisers of an annual historic racing meet here are trying to convince Kork to put one of his championship bikes on the track later this year, or early next year. Maybe I'll have to contact him and see if he needs a spannerman.

Keep us informed.