From fullnoise.com
Wednesday, 13th September, 2006 -
After Honda announced recently that it would discontinue it's 2-stroke range, Yamaha has come out and stated it will continue to manufacture and sell it two-stroke MX bikes.
"Despite some doomsayers predicting the demise of the two-stoke engine due to environmental concerns, Yamaha is fully behind the continuing development of its class leading YZ machines," Yamaha announced in a press release.
YMA Director/General Manager Steven Cotterell points out: "The two-stroke engine certainly has a place in competition motocross today. Our YZ machines continue to sell in great numbers to a dedicated fan base who prefer owning and riding two-strokes."
"Yamaha has developed the YZ range into state-of the-art machinery powered by compact, free-revving engines running in advanced aluminium frames. There is no plan to cease development of these bikes in the near future," adds Cotterell.
motometal said:when they speak of the sucess of the UniCam engine, that statement could easilly be criticized...
motometal said:The UniCam has not exactly been a slam dunk reliability/maintenance cost wise due to the intake valves.
motometal said:If it weren't for magazine tests and the readers egos (most riders could go just as fast with a few less hp but they either don't realize it or won't admit it to themselves), the mx bikes could come standard with a bit more conservative components (a bit milder cams, SS valves inteaad of titanium, pistons with longer skirts, etc.) which would give more than enough performance for 90% of the riders. The hard core A class racers or anyone else that feels they must have ultimate performance, could buy the bolt ons as required.
motometal said:Sorry as I'm sure this has been asked and answered many times, but regarding the CR450 conversion to SS valves (Kibblewhite, etc.), after an engine is switched over, is there a measureable horsepower decrease on a dyno?
motometal said:I can't remember if this requires stiffer springs.
motometal said:Assuming minimal power difference, this seems like a win-win proposition. If the engine with SS valves will run nearly the same on a dyno and the valves/seats last much longer, what's the real-world advantage of Ti valves?
Rich Rohrich said:"Introduce a direct injection two-stroke MX bike with it's associated costs and teething issues and people will be lining up to bitch about that soon enough. ;)"
motometal said:The UniCam has not exactly been a slam dunk reliability/maintenance cost wise due to the intake valves. I acknowledge that sometimes we must move backwards first to go forwards. In my opinion, Honda has sacrificed some of the values the company was built on. Not limited to four strokes...comparing a 2001 and 2002 or newer CR250 side by side shows a real contrast, in my opinion.
MTK, do you have any thoughts on this since you own two bikes similar to my reference (I used to)?
jimt_yz400 said:What's the cost of the SS valves, Ti retainers and springs?
Is it extremely expensive? I need to rebiuild by son's MX CRF450 where he puts an incredible amount of time on it, so maybe this is a good bet for durability.
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