Lots of changes.....
http://www.dirtrider.com/features/first-look-all-new-2014-yamaha-yz250f-and-yz450f/
http://www.dirtrider.com/features/first-look-all-new-2014-yamaha-yz250f-and-yz450f/
2014 YZ450F + 250F bows
- Thread starter gasgasman
- Start date
blitz11
Silver Level Site Supporter
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.
GMP
Active member
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.
, 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.
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.
, 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.
GMP
Active member
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
Sent from my iPad using Tapatalk HD
GMP
Active member
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.
"Not sent from my iPad using Tapatalk HD", pretty funny.
Do you still need technique with the EFI bikes?
The technique I use;
Engine is shut off using kill switch - locate TDC, one long stroke of the kick starter ( if you kick too quickly the EFI doesn't get a long enough power pulse to activate ).
Just crashed and burned - try above , if that doesn't work then pull throttle full on, kick over three times to clear engine ( full throttle while engine is not running stops the fuel supply ), close throttle and find TDC one kick and your away.
It's really that simple.
Your right on the " no free lunch " bit. With the Yamaha's the trade off is a very crude injection system ( closed loop as with most other bikes ). The injection makes the throttle response very abrupt off idle, very noticeable on the 450 ( some of this can be tuned out of the OEM system ). With the tuner however the Yamaha's are easy to remap and it's surprisingly effective.
Otherwise I find my 450 pretty easy to live with TBH. One thing people never do is tune the "CO" setting, the GYTR tuner can not do this. Think of the CO setting as a mixture screw setting.
I am looking forward to sinking my teeth into the new 250. The old carb model needed a ton of work to get it fueling right but injection "should" resolve those issues. Being a new 4valve design the horrible step on the intake should be gone for a start ( one would hope ). This motor with its new architecture should technically really breath, a real bonus when your pulling some numbers.
Make sure you drop back with some feedback on them GMP , you guys will get them in the states long before us :-/ .
One thing I did notice was a single comp ring - better be prepared for frequent top end strip downs....
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