Hi folks,I've just bought my self a '72 250 Ossa Mar.I had one in the late '70's,purchased from one of the staff at Windsor Comp Shop.It was fitted with a reed valve when i got it,and it rode better than my mates 310.I would like to fit one to my bike,any ideas where i could get one?

I think you'd need to source a barrel that has already been converted.
But it won't be cheap, the last one I saw for sale Steve Sells was selling and he wanted £400 for the barrel, cage & reeds, head and piston.
He's pretty reasonable with his prices!

There were a couple of companies that converted them, Romatt as one, can't for the life me remember the other.

They machined the fins off and screwed a reed cage on, obviously position is important!
From looking at my Romatt conversion looks like early TY250 reeds were used in a specially made cage (Embossed with "Romatt")
A paper gasket seals up the cage and barrel.

Edited July 6, 201511 yr by goudrons

HI Goudrons,thanks for the reply.looks like it will be staying standard,unless any thing else turns up.All the best.

 

There were a couple of companies that converted them, Romatt as one, can't for the life me remember the other.

Harpower rings a bell as the other reed converter.

There are plenty of other ways to crisp the motor up before thinking about reed valves.

A decent carb for a start.

I've had mine running on both Mikuni VM26 and a 24mm and 26mm VHST.

Basically they'll run pretty much what a Beta Rev3 will run on, Mikuni VM's are pretty cheap and easy to tune.

The exhaust might need some work too.

They run pretty well with or without a silencer, the silencer was only held on with a spring so could be removed easily for "competition".

So start with the mid box, they'll no doubt be nothing left in it except a perforated tube.

Split it, wrap the tube in stainless wire wool and weld it back together.

There was a longer front pipe fitted to the later Verde (green) models that tend to increase the torque slightly, if you can find one, it's worth a try.

As written, the silencer is just that, as long as it's not choking up the gases and it's not getting in the way.

Some fit a thinner head gasket as the original is quite thick, this decreases the squish gap, some meat needs removing from the heads mating surface to get it to pull down on the barrel without it leaking.

I found that changing the front sprocket from 11t to 10t works well (10/44), makes second gear much more usable.

A new nut is needed to hold it on, it's machined with a collar to allow the chain to pass without fouling it, available from InMotion.

Edited July 8, 201511 yr by goudrons

Thanks for the imfo.With the reed valve i was just harping back to my youth.The windsor comp shop Ossa was really trick for the day,reed valve.beautifully crafted bash plate and dzus fasteners on the side panels,really fond memories!