Motocross All 250f engines will follow Yamaha's design

[cummins1320]

Mark my words....  IMO the other manufacturers can not ignore the reverse engine design makes more power.

 

flame away

 

 

[DethWshBkr_]

Guess you forget to look and see that the KTM 250SXF makes far more peak horsepower than any other 250f (stock).   The Yamaha has more torque, but a good bit less horsepower.

Edited July 13, 2014 by DethWshBkr_

[Fade]

Guess you forget to look and see that the KTM 250SXF makes far more horsepower than any other 250f (stock).   The Yamaha has more torque, but a good bit less horsepower.

http://www.motorcycle-usa.com/11/17764/Motorcycle-Article/2014-250-Motocross-Shootout.aspx

 

"A good bit"

 

K.

 

Edit:

 

Upon reading the last page, it seems every test rider chose the YZ250F.....something tells me they knocked it out of the park this year... and it's got a red plate right now.

Edited July 13, 2014 by Fade

[yz133rider]

The yamahas are getting the holeshots more often then not in the 250 class for sure. And if not the holeshot the top 5 around the turn seems to be very blue.

[GBowman]

It has more to do with the new head design then it does the reverse design. 

[Piney Woods]

Mark my words....  IMO the other manufacturers can not ignore the reverse engine design makes more power.

 

flame away

Blue kool aid?

[Fryboy]

Blue kool aid?

 

That shit tastes gooooood ! 

[Kev_XR]

Can we file this next to "all engines will be five valved soon."

Didn't the reverse head screw up weight distribution for Gen 1?

The only reason for a reverse head is for a better inlet tract or longer exhaust pipe.

A clean intake route is one reason the old non-linked KTMs made more power.

Other members of the Big 5 will try every trick before reversing the cylinder.

Cannondale got it 100% wrong trying to create a shorter exhaust pipe.

KTM and Kawasaki won the 250 motos yesterday.

Edited July 13, 2014 by Kev_XR

[Texas2Smoker]

F*** horsepower it's all about torque...

[GBowman]

Can we file this next to "all engines will be five valved soon."

Didn't the reverse head screw up weight distribution for Gen 1?

The only reason for a reverse head is for a better inlet tract or longer exhaust pipe.

A clean intake route is one reason the old non-linked KTMs made more power.

Other members of the Big 5 will try every trick before reversing the cylinder.

Cannondale got it 100% wrong trying to create a shorter exhaust pipe.

KTM and Kawasaki won the 250 motos yesterday.

They have 4 valves now. 

[DethWshBkr_]

http://www.motorcycle-usa.com/11/17764/Motorcycle-Article/2014-250-Motocross-Shootout.aspx

 

"A good bit"

 

K.

 

Edit:

 

Upon reading the last page, it seems every test rider chose the YZ250F.....something tells me they knocked it out of the park this year... and it's got a red plate right now.

 

Here's another magazine's numbers.

 

"....KTM 250SXF (42.89 ponies) and Kawasaki KX250F (41.16 ponies), the YZ250F, at 40.61 horsepower....."

 

I really don't care what the numbers show on a given day.  

 

Of course the Yamaha has the red plate.  Tomac and Roczen moved up to the 450's.

[MotorBoatin]

Can we file this next to "all engines will be five valved soon."

Didn't the reverse head screw up weight distribution for Gen 1?

The only reason for a reverse head is for a better inlet tract or longer exhaust pipe.

A clean intake route is one reason the old non-linked KTMs made more power.

Other members of the Big 5 will try every trick before reversing the cylinder.

Cannondale got it 100% wrong trying to create a shorter exhaust pipe.

KTM and Kawasaki won the 250 motos yesterday.

All the manufactures know how to make engines. The problem with motocross is the chassis interferes with engine design. High ground clearance and a low gas tank makes for short engines. Yamaha's reverse engine helps create more room for the head

Here is a pic of two KTM 250's one road one dirt

Edited July 13, 2014 by meyermetal

[sokudo]

It is not the HP that gets the hole shot but more the torque 

[Kev_XR]

All the manufactures know how to make engines. The problem with motocross is the chassis interferes with engine design. High ground clearance and a low gas tank makes for short engines. Yamaha's reverse engine helps create more room for the head

Here is a pic of two KTM 250's one road one dirt

Per motogp3 rules 250cc engines cannot be based on the motocross engine. It looks like KTM tilts the cylinder forward on the moto3 engine and has the cases lower for oil cooling. I see nothing to show any influence of the YZF reversed cylinder design.

http://blog.ktm.com/moto3-vs-mx2-just-dirt-bike-engines-in-a-grand-prix-chassis/

http://www.asphaltandrubber.com/motogp/motogp-penalty-points-update-moto3-chassis-price-cap/

Edited July 14, 2014 by Kev_XR

[Kev_XR]

They have 4 valves now.

My point exactly. I was mocking the old 5 valve Yamaha design.

Maybe reversed cylinders work better.

or maybe Yamaha spins them back in 5 years.

https://www.thumpertalk.com/topic/358258-yamaha-drops-the-5-valve-head-on-the-07-r1/

[MotorBoatin]

Per motogp3 rules 250cc engines cannot be based on the motocross engine. It looks like KTM tilts the cylinder forward on the moto3 engine and has the cases lower for oil cooling. I see nothing to show any influence of the YZF reversed cylinder design.

Did I say Yamaha was influenced by KTM's design?

More room for the engine equals new head design and the front intake is more efficient

Pay attention

The third major key lies in the revamping of the YZ’s reverse-mounted DOHC cylinder head. The new downdraft design, which places the air filter right behind the steering head, allows the intake charge a 30-degree straighter shot into the combustion chamber, and its symmetrical ports increase velocity while reducing turbulence for better cylinder filling. The new four-valve head also carries one less intake valve, utilizing titanium valves that measure 31mm on the intake side and 25mm on the exhaust. The valve angle is also a much narrower 23.7 degrees compared to 30.5 degrees on the old motor.

Edited July 14, 2014 by meyermetal

[KTMRider4Life]

Did I say Yamaha was influenced by KTM's design?

More room for the engine equals new head design and the front intake is more efficient

Pay attention

They're also looking for a different power profile in the two motors too. 

[MotorBoatin]

They're also looking for a different power profile in the two motors too.

Yes but more efficient is more efficient and when it comes to carbs or throttle bodies a straight intake port is better. The reverse engine has a better intake track than traditional MX engines

The design obviously caused other issues......just ask Bubba

[KTMRider4Life]

Yes but more efficient is more efficient and when it comes to carbs or throttle bodies a straight intake port is better. The reverse engine has a better intake track than traditional MX engines

The design obviously caused other issues......just ask Bubba

troll

[thsp485]

F*** horsepower it's all about torque...

100 % correct.