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YZ390 Injected Mock Up - FYI

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6 minutes ago, bullmastiff said:

Hmmmm.... what I took from the article is that mxa is a bunch of short whiners..

 

 

I like your username.

Here's my female mastiff.

She's Bella. Her dad was a bullmastiff and mom's a cane corso

She's about 8 months now. First pick is when I got her at 9 weeks

Second is this past week. She's about 85 pounds now. 

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14 hours ago, SDTony 325 said:

What is the Future?

With Motocross Action Magazine doing articles like this to support a Big Bore  https://motocrossactionmag.com/ride-tms-2017-300mx-world-two-stroke-championship-racer/, the world is getting closer to a Yamaha 300, 350 or 400.

YZ390.....

http://2smokin.com/yamaha-yz390-injected/

 

 

 

Couldn't a well tuned 325 match, or exceed the 450 four stroke class bikes?
ie, I've read several instances where people with 300's claimed the same

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22 hours ago, Blackwoodz said:

Here's my female mastiff.

Maybe getting off topic a little?  I love dogs too. Makes me smile to read comments like yours. Lots of joy.

So about the YZ390 frame choice. That article was written in 2015, so he used the current 450 frame in his visual mock-up. That frame was considered a dud by most, with odd flex and geometry, and too difficult to setup good handling balance. Today's 2018 450 frame should be much better.  But I guess it'd still be too rigid for/aft so unsettled for a 2 stroke, and maybe a bit too fat up front for an agile bike.

The 2004 YZ250 steel frame would be the perfect choice. Plenty stiff and strong, but without the vibration felt with alum.  The 2004 frame allows a front end that will respond precisely to front steering. 

A 390cc modern 2 stroke would be awesome. Super broad power and low running cost with long hours between rebuilds.

Of course none of this will ever happen.  The European brands own the new 2 stroke market and they are very well setup to produce high performance steel frames. Leaving the Japs in their dust with alum frames and the heavy feeling thumpers.

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14 hours ago, JohnBee said:

Couldn't a well tuned 325 match, or exceed the 450 four stroke class bikes?
ie, I've read several instances where people with 300's claimed the same

Real track experience while running along side of a 450 the YZ 325 has the same Torque level (Dyno Chart shows this as 33 lbs. Torque) but the 450 pulls longer. You could also say that a 450 has a broader power band. I also observed this when a KTM SX 300 (big bore 250) ran alongside of a 2016 KTM 450.

 

So the 325 gets you close to a 450 but not quite the same broad power band, it may take a 400 or similar size.

Edited by SDTony 325
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21 minutes ago, SDTony 325 said:

Real track experience while running along side of a 450 the YZ 325 has the same Torque level (Dyno Chart shows this as 33 lbs. Torque) but the 450 pulls longer. You could also say that a 450 has a broader power band. I also observed this when a KTM SX 300 (big bore 250) ran alongside of a 2016 KTM 450.

 

So the 325 gets you close to a 450 but not quite the same broad power band, it may take a 400 or similar size.

Very interesting.  Would be curious to see what adjustments could be made to flatten out the power curve on the 2t side of things however. ie, porting, head geometry, crank,carb, reeds, pipe and timing, could all be adjusted to shape the power curve and favor a particular rpm distribution.  TBH, I've never driven a detuned 325, though I'd love to know what's possible in terms of power curve distribution on a big bore two stroke. 

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The problem is the motors are way out of date. If they picked an arbitrary point, they would have to reduce the size several times depending on how much tech they let them use. With computer controlled variable intake and exhaust they could get nutso. On the pipe from idle till it blows with very steep cone angles. Bet a 250 could make 80hp or more that way with a broad spread.

Edited by Oic0

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Very good points, the 325 is probably good for most guys. The good riders would win against a 450 because down the straights there is little difference but cutting inside on the corners would win. Eddie (Eddie) Sanders Racing has said that the 300 just was not quite a match to the 450, so this is why he designed a 325.

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1 hour ago, Oic0 said:

The problem is the motors are way out of date. If they picked an arbitrary point, they would have to reduce the size several times depending on how much tech they let them use. With computer controlled variable intake and exhaust they could get nutso. On the pipe from idle till it blows with very steep cone angles. Bet a 250 could make 80hp or more that way with a broad spread.

Good point.

The simple solution is to define classes with intake restrictor plates. Do whatever you want with what ever size motor you want, provided that the intake sucks air through a hole of a specific size. No forced fed of course. That'll kill the advantage to the big dollar 250F teams, and 2 or 4 stroke doesn't matter in the class rules. HP would be capped and torque spread would win, so I assume that means bigger motors would win.

As a bonus, having combustion engine power defined by restrictor plate could make it easier to introduce e-bikes into each class. Although a problem with electric motors with the same peak HP is that they can produce peak torque from 0 RPM.

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9 minutes ago, SDTony 325 said:

Very good points, the 325 is probably good for most guys. The good riders would win against a 450 because down the straights there is little difference but cutting inside on the corners would win. Eddie (Eddie) Sanders Racing has said that the 300 just was not quite a match to the 450, so this is why he designed a 325.

I agree that more time is gained/lost in corners than straights, and the rider is the biggest difference.  But the problem is that the sprint out of any start gate is a straight.

Something important to remember is that a well tuned and good handling 300+ cc 2 stroke is a lot more fun on most tracks (MX or technical offroad) than any 450F.   When we crash on 450s it's usually far worse too. Massive wrecks and hospital visits are common and when you touch a foot down in a bad place the heavy 450s are knee/leg busters. Besides the fun and cost benefits, I guess the injury factor has a lot to do with the resurgence of 2 strokes.

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To say it bluntly, 90% of the riders out there would be happier on a 300, 325, 350 or 400 2-T! Why, with good Jetting (my jettng is spot on) / Fuel Injection on a 2-T the FUN FACTOR goes up 3 times with less weight and more Torque! Remember these size Engine's will not work as hard and therefore have lower service / repair cost.

Yamaha should listen to this and produce a 350 or 400 2-T, but they will not because they have calculated that 4-T parts revenue is a good thing.

Based on this growing the Off-Road World is NOT a Corporate Goal.

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