• Hi everyone,

    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

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WOW!!! Ossa with a EFI 2 stroke reverse head

Motosportz

Motosportz

CH Sponsor
Staff member
I can hardly wait until this layout / EFI 2 stoke ends up in a off road bike. After hearing nothing but raves for the new YZF450 with the similar engine layout and having ridden the 390 Berg extensively doing this with a 2 stroke is going to make it ridiculously light feeling.

710321797_dMp4f-M.jpg


710321806_B4LvS-M.jpg
 
That is awesome!

I want one, think they will trade straight across for a lightly used Sherco?

No one knows what an OSSA is anyway. :lol:

Later,
 
Pipes will be the problem on other two stroke applications. You can get by on a trials bike because they don't use "expansion chambers". But, there are other ways around that, too.
 
Seems exactly the opposite of what Berg is doing, Yamaha is going for a more vertical stroke, Berg is going more horizontal.

I don't know a damn thing about this, but does direct injection (vs regular old efi) get rid of the need for an expansion chamber at all? I know one of the main reasons for an expansion chamber is trying not to blow all of your fuel out the exhaust, you are trading off scavenging to prevent wasting fuel, but if the fuel isn't with the air then I would think you could use a port design aimed just at really good scavenging, blow everything right out with no regard for using the expansion chamber resonance to stop the flow out the exhaust port at the right time. So in that perfect world, where you blow all of the old charge out the exhaust port, you would end up with more oxygen in the cylinder for the next charge as well as possibly having a more traditional header.

Or at least, that's what my uneducated mind is hoping for, because I can't seem to get a single ride in without denting my new pipes.
 
speedkills;58707 said:
Seems exactly the opposite of what Berg is doing, Yamaha is going for a more vertical stroke, Berg is going more horizontal.
Click to expand...

Not really, both approaches are aimed at moving the weight more towards the center of the bike.

speedkills;58707 said:
I don't know a damn thing about this, but does direct injection (vs regular old efi) get rid of the need for an expansion chamber at all?
Click to expand...

No, the expansion chamber is needed to tune the combustion cycle. It is the equivalent of a valve in a 4 st controlling the cycle timing. On a Trails bike that can be much smaller as they need to operate over a different range.
 
Motosportz;58717 said:
Not really, both approaches are aimed at moving the weight more towards the center of the bike.



No, the expansion chamber is needed to tune the combustion cycle. It is the equivalent of a valve in a 4 st controlling the cycle timing. On a Trails bike that can be much smaller as they need to operate over a different range.
Click to expand...

Guess I'll need to go low tech and invest in a pipe guard.

From the looks of the angle I thought Yamaha was just going for straight mass centralization while Berg looked more like they were trying to alight the stroke more closely with the roll center to reduce the effort required to flick the bike side to side. I'm curious if the changes on both brands will feel similar.
 
jmetteer;58699 said:
That is awesome! No one knows what an OSSA is anyway. :lol:
Click to expand...

:thinking: I do...

Some older members rode them in our club. Ron Walsh.

I've been waiting for this and hope Gas Gas gets on board soon...oh ya Husky too.:D

:cheers:
 
I've been looking for an OSSA Mick Andrews Replica (MAR) for Vintage Trials. Screw that..... I'm buying one of those, sh!t economy or not!:cheers:
 
jmetteer;58699 said:
That is awesome!


No one knows what an OSSA is anyway. :lol:

Later,
Click to expand...

I do. I used to want to own a Stiletto. I've ridden a Stiletto and a Plonker, too. I guess they aren't going to call that new model a Plonker.:D
 
Dirtdame;58810 said:
I do. I used to want to own a Stiletto. I've ridden a Stiletto and a Plonker, too. I guess they aren't going to call that new model a Plonker.:D
Click to expand...

You guys don't count, you ride the boutique brand Husky. :D

I am a bit to young to have ridden OSSA's but do know about them.

That was supposed to be funny based on my trying to trade my "well known" Sherco for the "unknown" OSSA. Sherco isn't exactly a household name. ;)

Later,
 
jmetteer;58699 said:
That is awesome!

I want one, think they will trade straight across for a lightly used Sherco?

No one knows what an OSSA is anyway. :lol:

Later,
Click to expand...

I very much remember Ossa. I always thought that the Pioneer was a pretty cool bike and I loved the Yankee 500 with the indexable crankshaft.:thumbsup:
 
jmetteer;58813 said:
You guys don't count, you ride the boutique brand Husky. :D

I am a bit to young to have ridden OSSA's but do know about them.

That was supposed to be funny based on my trying to trade my "well known" Sherco for the "unknown" OSSA. Sherco isn't exactly a household name. ;)

Later,
Click to expand...

Whats a Sherco?



:lol::lol::lol:
 
Yippee Ossa's are back. Must finish the restoration of my 73 ISDE 250 what a machine-made the Bultacos and Montessa look ordinary-up there with the mughty Husky's Maico's and CZ's in performance
 
I love our moto passion/hobby,, the resurrection of the OSSA name fantastic!! Viva Espana!!!
when all the usual naysayers of anything non-Japanese find out what OSSA stands for there will be all sorts of camera/projector/movie or whatever jokes they can find.
Spain has a very good standing record for getting trials machines off the ground then bulding "regular" bikes (read Gas Gas).

Orpheo Sincronic Sociedad Anónima (O.S.S.A.) and later by Maquinaria Cinematográfica, S.A., founded by Manuel Giró, an industrialist from Barcelona
 
speedkills;58707 said:
I don't know a damn thing about this, but does direct injection (vs regular old efi) get rid of the need for an expansion chamber at all? I know one of the main reasons for an expansion chamber is trying not to blow all of your fuel out the exhaust
Click to expand...
an expansion chamber is the "supercharger" of the two-stroke exhaust. it helps scavenging and increases power up to 75%. a two-stroke engine without a tuned pipe has the performance of a four-stroke engine. for this reason, trials bikes don't really have anything worth calling an "expansion chamber". they don't need that much power, but they really need a flat torque curve.

even with fuel injection of any kind, you need an expansion chamber if you want power (and that's what we all want, right?).

the system they use is not a direct injection system. it's not even anything i would call a semi-direct injection. see:
g_galerie_3568_8.jpg


r

edit: i don't think that this packaging will affect the handling much, because the crankshaft is still in the same position. i think they did it mostly for packaging reasons, and to be different from the rest.
 
It has a flatter torque curve like a four stroke for sure, but to say the same performance isn't quite accurate. But yeah, I could see how you just aren't going to get the same volume of oxygen in the cylinder without that reversion wave from the expansion chamber now that I think about it more.

Now if only it wasn't for packaging concerns an external supercharger could solve those issues with a much broader powerband as it wouldn't have to be tuned to a specific rpm range. :thumbsup:

Boost, the replacement for displacement!



rasputin;58951 said:
an expansion chamber is the "supercharger" of the two-stroke exhaust. it helps scavenging and increases power up to 75%. a two-stroke engine without a tuned pipe has the performance of a four-stroke engine. for this reason, trials bikes don't really have anything worth calling an "expansion chamber". they don't need that much power, but they really need a flat torque curve.

even with fuel injection of any kind, you need an expansion chamber if you want power (and that's what we all want, right?).

the system they use is not a direct injection system. it's not even anything i would call a semi-direct injection. see:
g_galerie_3568_8.jpg


r
Click to expand...
 
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