OK EVO,it was your idea........

[Jeram]

Modern Porting - well there's porting appropriate to the design of the engine / it's intended use.  Much like "modern Expansion Chambers", that are thrown around here.

Modern porting meaning modern ducting.
This takes alot more R&D than KTM has done to get it right. Very few two stroke companies have understood this topic well enough to get it right.
It takes a little bit of additional knowledge to begin and a lot of R&D to get to where you want to be.

[factoryX]

So where does the cylinder spacer go?

Under the cylinder kind of like 87-89 trx250r's had.

[TMKIWI]

This is funny.
Modern high tech 4 stroke development? " title="Roll Eyes" class="smiley">

Peugeot came out with a twin cam 4 valve engine in 1912.
DeSoto had EFI in 1958.

And 2 strokes.
The Expansion chamber was designed for the V1 rocket and first used on a 2 stroke in 1938.
You want DI ?, First developed in 1902.
AR combustion, Trapping valves or CI have all been done.

Nothing earth shattering is coming for the ICE ( Internal combustion engine ).
Everything is just an improvment on an old design.
Everything "modern" has come about because of electronics ( in design and the use of computers ) and improvments in metallurgy.
The ONLY thing stopping more money being spent on 2 stroke development is the RULES. " title="Angry" class="smiley">
Just be happy with what we have, as the 2 stroke we have is still a bloody good engine.
Even with 15 years of "development" on the 4 stroke, cc for cc it still can not match our "old tech" 2 stroke.
Carry on.

[Stusmoke]

This is funny.
Modern high tech 4 stroke development? " title="Roll Eyes" class="smiley">

Peugeot came out with a twin cam 4 valve engine in 1912.
DeSoto had EFI in 1958.

And 2 strokes.
The Expansion chamber was designed for the V1 rocket and first used on a 2 stroke in 1938.
You want DI ?, First developed in 1902.
AR combustion, Trapping valves or CI have all been done.

Nothing earth shattering is coming for the ICE ( Internal combustion engine ).
Everything is just an improvment on an old design.
Everything "modern" has come about because of electronics ( in design and the use of computers ) and improvments in metallurgy.
The ONLY thing stopping more money being spent on 2 stroke development is the RULES. " title="Angry" class="smiley">
Just be happy with what we have, as the 2 stroke we have is still a bloody good engine.
Even with 15 years of "development" on the 4 stroke, cc for cc it still can not match our "old tech" 2 stroke.
Carry on.

Shut down. Realistically, the only major thing that happened to the four stroke since whats-his-face fired the first one up in whenever, is the OHC design. Other than that, everything has been an improvement on an old design. Same with computers, its the exact same tech as the room sized computers from 1950s. Just smaller. My SGS2 out performs the computers from 1950 a thousand to one. and Its a pHone.

[factoryX]

Try again, most modern build computers are about 20 of those rooms haha

[evo550]

So where does the cylinder spacer go?

Under the cylinder kind of like 87-89 trx250r's had.

So if it requires a spacer under the cylinder, I'm assuming with no rebore the yz piston is taller from the gudeon pin to the crown ? How does that increase the capacity by 25cc?

[ford832]

Ford, you are just as crazy as the Maico nuts.....

Omg,can it possibly be that bad? Noooooooooooooooooooooooooooooo

[factoryX]

Ah its been awhile, they used an slightly older piston(90's) It relocates the wrist pin, and I believe runs a 68.5mm bore. Its a 3mm spacer for the short rod 85/86 atc250r, and 2.5mm spacer for the long rod 87-89 trx250r. Again its only a slight bore on the steel cylinders, and most aftermarket 265cc cylinders ran this set up. At the end of this thread someone actually bolts up a later 02-10 piston, no other details. I wish I still had all the info I had stock piled when I owned a trx250r back in 08-09.

[evo550]

Ah its been awhile, they used an slightly older piston(90's) It relocates the wrist pin, and I believe runs a 68.5mm bore. Its a 3mm spacer for the short rod 85/86 atc250r, and 2.5mm spacer for the long rod 87-89 trx250r. Again its only a slight bore on the steel cylinders, and most aftermarket 265cc cylinders ran this set up. At the end of this thread someone actually bolts up a later 02-10 piston, no other details. I wish I still had all the info I had stock piled when I owned a trx250r back in 08-09.

But I still don't see how a 3mm spacer under the cylinder can increase capacity, only way to do that is bore or stroke increase.

[ford832]

If nothing else,it would lower the compression nicely. 

[evo550]

If nothing else,it would lower the compression nicely. 

Compression Smeshion, I have E-Start...

[evo550]

and so in rebuttal for the affirmative "KTM 300's are best" team,  I present our closing argument (put it together this w/end with a couple of my mates)
Please ensure, you have speakers at 100%, expand to full screen, and have a full frosty one ( in Fords case a Labatt's Lite  ) sit back and enjoy.
https://www.youtube.com/watch?feature=player_embedded&v=-cwImtQw3WA

[factoryX]

By increasing deck height its stroking it. Also, its no longer using the 66mm bore, its going to a 68.5(250r cylinders can be punched out to 70+mm pistons on the stock liners). So you have increased stroke and bore. Pretty simple. However, in that thread it mentions the stock bore on modern yz's being the same in the 66mm area, it shows a atc/trx250r piston side by side with a 02-10 yz250 piston. At the end of the thread someone mentions throwing a modernd yz piston in. no other details. It would be a 250 still.

Think of it this way, an old yz250 trick in the eighties was using a 490 rod with a 250 piston and throwing a large spacer under the cylinder. By increasing stroke its increasing displacement.

[ford832]

and so in rebuttal for the affirmative "KTM 300's are best" team,  I present our closing argument (put it together this w/end with a couple of my mates)
Please ensure, you have speakers at 100%, expand to full screen, and have a full frosty one ( in Fords case a Labatt's Lite  ) sit back and enjoy.
https://www.youtube.com/watch?feature=player_embedded&v=-cwImtQw3WA

That's a cool vid.The woods guy is ridiculously talented.In my case though,I avoid anything that is tagged "lite" like the plague-esp beer.
When I get even older and slower I may find it to be in my interests to track down a "YZ lite" I may be on a KTM 300 yet,you never know.  

[evo550]

By increasing deck height its stroking it. Also, its no longer using the 66mm bore, its going to a 68.5(250r cylinders can be punched out to 70+mm pistons on the stock liners). So you have increased stroke and bore. Pretty simple. However, in that thread it mentions the stock bore on modern yz's being the same in the 66mm area, it shows a atc/trx250r piston side by side with a 02-10 yz250 piston. At the end of the thread someone mentions throwing a modernd yz piston in. no other details. It would be a 250 still.

Think of it this way, an old yz250 trick in the eighties was using a 490 rod with a 250 piston and throwing a large spacer under the cylinder. By increasing stroke its increasing displacement.

That's what I was thinking you where thinking.. but increasing deck height or rod length doesn't increase stroke. Distance between big end pin and crank center x 2 does.