Yamaha bringing back the 2 Strokes..

[welterracer]

I just copy and pasted this from another site..

This according to the latest issue of Dirt Bike magazine...

I just got back from Barnes & Knoble (sp???). I went there to check and see if any of the spring snomo mags were in yet as last year they got them before the subscribers did. Anyway, there was no sled mags so I decided to check out a couple dirt bike mags (my summer hobby). To my dissapointment there was no Dirt Rider so I picked up the next best thing, Dirt Bike. On the cover there was some little blurb about a shocking new engine from Yamaha. So, I rushed to the contents page and then rushed to the story on pg 92. And low and behold I say a shiny new blue bike with a big fat 2 stroke pipe hanging off it. So what brought about this drastic change in course you ask??? Well, the AMA changed it's rules for the amatuer 250 class and are now going to allow 250cc two stroke bikes in the 250cc four stroke class. So why the change in rules??? Well, it's the cost and hassle of maintaining the new super high strung 4 stroke engines that need very frequent valve adjustments, complete top end rebuilds, and that use exotic exhaust material. They said that the two strokes were cheaper to build, cheaper to buy, cheaper and easier to re-build, and get this...MORE DURABLE !!!! Oh yeah, and they also mentioned a higher power to weight ratio...Hmmmmm...
This article kinda reminded me about hearing about the recommended service life of a CR250F piston, it's 30 hours!!! These bikes are not your father's XR. Those things would run for ever and it's from bikes like those that give people the impression / perception of superior four stroke reliability. These new super high output 4 strokes are having to be so high strung to try and compete with 2 strokes in the power to weight ratio department that their traditional reliability is going out the window. Think about it, yes our cars and trucks run forever but how long do the Nascar or racing sport bike engines last??? I was thinking that if Doo pulled of this direct injection thing that we might see 2 strokes creep back into the four wheeler and off-road bike segments but I was thinking that it would be a few years down the road. This really took me by surprise. I wonder if the boys over on Totally Yamaha are aware of it???

 

[BlueByYou2000]

I was not aware of this and would like to see a copy of the magazine and read the article. I would find it very surpirising it if were true. The comparison to a four stroke car and truck to NASCAR is just plain silly. I think its pretty clear how well built EVERY Yamaha 4 stroke engine has been. It is very difficult to find engine failures from members here. And that is going back to the 03 RX-1. All you have to do is log onto Dootalk, HCS, and Polarisfiles to find the exact opposite.

The single constant quality component that Yamaha has delivered to its snowmobile consumer, is ENGINE QUALITY,period!

 

[DoktorC]

I wonder if the RZ500 is next?!?!?!?

 

[Aaron Eh]

Dirt Bike magazine is oriented more to Cross Country style racing and riding. The two stroke is still a very popular choice for teams running in these circuits. I have one of each 06 YZ250 and a 07 RM-Z250. The RM-Z is used only on the MX track. The YZ is a general purpose bike used for trails, track and sand.

BlueByYou2000 why are you so skeptical? The two stroke is so simple that a rebuild is usually a piston and rings. The four strokes have those parts plus you have to worry about valves and valve seats. It can be expensive to have your seats machined and replace 5 titanium vavles.

Four strokes have had a displacement advantage over two stroke in MX which is why they have ruled the roost. They both have their advantages thankfully Yamaha is still allowing the consumer make the choice - I can still by a 125 if I wanted!

 

[Tork]

actually in all kinds of racing rule changes have happened to keep all kinds of motorsports racing more affordable.

The trouble always is particularily manufacturers have such DEEP pockets. So they go more and more exotic trying to out do the others.
Going 2S would be a way to open things up to more people possibly the average guy.

I dont think it will effect us consumers though. I think the future for us is 4 stroke with the possible exception of direct injection 2 strokes ending up being rock solid reliable and that wont be known for a while yet.

 

[welterracer]

I personally find it hard to belive that the 2 stroke can be as realiable as compared to a 4 stroke and i havent seen it yet..

Not too many 2 strokes out there that can last 30,000 miles running at almost 11,000 RPMs most of the time.. (like we have seen with some of the sleds on this site)

 

[Aaron Eh]

I've seen one sled with 30000 + miles. Hondo said he spends most of his time in the around 6000 rpm's +/- 1000 rpms.

Dirt is way more harsh than snow. So much potential to suck in dust and grind away your engine internals.

Besides we are talking about making it to the end of the race reliability. Dollar for dollar two strokes are the way to go for grassroots.

 

[EsonPZ]

You really cant compare the 4s engine in a dirtbike to the ones we have in our sleds. The dirtbike engine is a race engine!
The only reason i ride a YZ 125 instead of a YZF 250 is the higher maintanence costs of the 4s YZF 250.

And the reason i have a Nytro is the supreme durability of the 4s engine compared to any 2s sled engine.

 

[BLUEBALLER]

APRIL FOOLS!!

 

[Mighty]

It is true that the AMA changed the rules and are forcing the 250 class 4-strokes to run with the 250 2-strokes while the 450's run in a class all by themselves. I was at my dealer about 2 weeks ago and he was frantically trying to dealer trade for YZ250 2-strokes without any luck.

I don't know if Yamaha is coming out with a new 2-stroke but after reading that article and being at my dealer I can see them doing so.......

As far as reliability goes, I had a 1986 YZ250 for over 14 years and never put a wrench to it. When the season was over I drained the fuel, poured some oil in the cylinder and plugged the exhaust.

I'm seriously thinking of picking up another couple year old 2-smoke YZ......

 

[Aaron Eh]

The 05's and up have nice aluminum frames.

 

[Tork]

No question that 2 strokes have had pretty decent reliability historically until emissions and very high HP came into play.

Trying to run leaner and with less oil has caused some pretty big problems.

But for racing, it only has to stay together for the race. Street versions will be somewhat detuned and they will probably do OK as well.[/b]

 

[Aaron Eh]

30:1 Premix!

These aren't street bikes here - these are off road competition models. No emissions testing for these.

 

[Silver]

Yes in the world of off road racing 2 smokes are king.I race enduros here in Mi.I have a 01 YZ 426( for sale) and a 2007 Gas gas EC 250(awesome bike).Lets just say the 4 stroke only got rode 2 times around the yard.For the tight single track a 2 stroke is hard to beat.Yes AMA rules have changed, to what was mentioned in other posts.Biggest reason I heard was for cost for amatuer racers if you've ever had to rebuild a 4 stroke you know what I'm talking about.Also the 250 2 strokes will take over the 250 f class as they make quite a bit more hp.I can also see honda and Kawaski getting back into building 2 stroke bikes again .I don't see Yamaha building any 2 stroke sleds as they sell enough 4 strokes no reason for the cost to build a 2 stroke injected sled.It would be cool to have one as a option but don't hold your breath.

 

[rapeape]

There are ZERO emissions on a MX bike, they are designed for "racing" only. Snowmobiles have to pass all of the EPA junk.

The AMA isn't making 250smokers run with 250 4strokers, they're allowing it in amateur racing only.

They fast guys will still be on the 4-strokes cuz they're faster and they put the power down better.