05 YZ 450 finally dialed in

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  • WEAL

Posted February 27, 2007 - 11:31 AM


After much trouble with carburation I finally suceeded and got the bike dialed in properly. Thanks to this forum I found a few tricks that helped the YZ even more to deliver the desired power. After having a 04 Honda 450 with zero problems, never even touched the carb, I was very disappointed with my first Yamaha. Almost everything inside the carb was way off - the first owner did only 5 hours on it and never rode it hard. I know for sure he never worked on that carb.

Inlet valve play was not within tolerances so I corrected that in the hope to cure my carb problem - hesitating throttle. Next I tried larger pj (48), this did not help.
Then I found the Float height 2mm low and thought thats where the problem was - corrected it and it got slightly better. I could set the idle at around 1500 with throttle returning there properly with the 48 pilot. As I desired to set the idle nearer 16 or 1700 the throttle hesitated again so in went the bored 45 jet, size 55 now. This did help again but raising the std needle two clips made it perfect. As I was already in there I did the ap o-ring mod as well and used an old Mikuni airjet with 0,55 as leakjet in the bowl. To get a bit more low end I fitted a heavier flywheel. Finally the weather got better and I was off to Italy to test the bike and have fun on a few very nice racetracks.
What can I say: finally this Yamaha behaves like a proper thumper - it starts first or second kick (hot/cold) and pulls my arms out of the sockets, does not bog or hesitate anywhere or under any situation so I guess I am finally there. This thing is now working as it should and if it stays that way I will keep it for this year. I don´t know how good the 06 engine really is - two of my buddies have big issues - one had a bent crank (brandnew bike, first owner) that destroyed the mains until I took the engine apart and checked everything and found that lousy crank. The other has a wrecked gearbox 2/3rd gear after about 50 hours. So I do hope my 05 is better and will wait to see how the 07 holds up - if there are no issues known this should be my next Yami.

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