2014 YZ450F + 250F bows
 

Lots of changes.....

http://www.dirtrider.com/features/fi...0f-and-yz450f/

Wonder if it will have the reliability of the 5 valve motor? I like it, from a design point anyway. Look closely at an '02 Cannondale and you will be amazed at what Yamaha has taken for '14.


Sent from my iPad using Tapatalk HD

If only Cannondale had wrapped the header around the cylinder they would have had a decent powerband to work with. Never rode one, but from the outside looking in the C-dale was a brilliant concept very poorly executed.

My colleague's 2006 WR450 has served 2 years as a dirt bike, and 5 years as a super-moto both on the street and for track days, something like 400 hours on the engine. He did another valve clearance check, and all 5 valves were in spec. If you stay off of the rev limiter (which he does except at the track), those motors will live. I give Yamaha credit for a good engine design.

Looks really cool, and could be a 450 that could be used in the woods...I would hate it is Yamaha isn't as durable as years gone by. I guess time will tell.

I tend to think the current Yamaha reliability is largely due to the five valve head design. Smaller, lighter valves have less inertia and use lighter springs. Think about where that design came from, its actually one slice of an older R1sport bike motor. Even their sleds use it now.

Steve,

I had a C'dale E440. Basic problem is they were too arrogant to progress slowly and learn how to produce an off road bike that works. Lots of thermal and electrical problems. The E440 was just the MX bike (very light flywheel)with a light and softer map, so when it got in the woods these issues that did not occur on the track reared their ugly head fast. Want to talk about re-engineering? I redesigned the entire power distribution system with SSRs and better noise supression, insulated the tank, airbox, fuel lines, ceramic coated header, etc., along with a LOT of custom mapping. The short header allowed blue flame out of the can you could see at night.:eek:, and it was loud. The motor was mechanically loud too and sounded like a Ducati. I had no mechanical issues at all because I addressed the problems immmediately. In the end the bike was pretty good as long as it was not too tight. It would run with a CRF450 of that era because it hooked up so much better. They made real good SM bikes and awesome ice racers. I just got tired of working on it trying to make it something it was not. I sold it to a guy who made a street legal SM out of it. One thing though, that bike was built VERY well. The fit and finnish was top notch, no BS there.

I have had a lot of Yamahas. I had one of the first 1998 YZ 400s and I rode it a lot without any problems whatsoever. My friend has a wr 450 that has a boatload of hours and the valves are still within spec, incredible. The Yamaha thumpers are tough, the 2014 should be too. Yamaha's RD is second to none.

What is nice is the exhaust is completely protected, and the muffler is small and forward. If it had decent engine manners it would be a great bike for woods. I get the impression that a lot of these newer EFI 250Fs don't like to lug down, or even run down low, and flame out easy. This goes for my brother's Husky 310 as well. One thing for sure though, when its slick and muddy, they seem very easy to ride. Guys in my class that are usually no problem to me seem to run a lot closer. If the flame out and hot start issues could be solved I might try one.


Sent from my iPad using Tapatalk HD

The 450's flame out as well with a stock map in the woods. A remap + turning the idle up a fraction stops this, it's super easy with the tuner. I couldn't imagine the 250's being any different.
Hot start issues??? It's all in the technique .

Not sent from my iPad using Tapatalk HD

I had a Cannondale I did a lot of mapping on and it worked pretty good for what it was. I'm going to sit and watch this one, there wil be a fair amount of these showing up in my series and it wil be obvious if its a viable option. The light weight, adequate power, and clean external profile is very attractive, but there is no free lunch.

"Not sent from my iPad using Tapatalk HD", pretty funny.