2002 YZ426F...needs help with low end

2 replies to this topic
  • yamaha879

Posted September 24, 2006 - 07:19 AM


I have had my 426 since I bought it new in '02. I have the bike setup just how I want it...suspension, controls, etc. The problem is my low end is minimal, but the mid and top are great. I have adjusted the cams, fuel screw, cleaned and re-jetted the carb. I need some guidence....any help would be great! Thanks

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  • PK

Posted September 24, 2006 - 09:29 AM


There is no replacement for displacement. Has the bike just recently lost it's low end or have you always thought it was weak?

Also, how do you adjust a cam?

  • Birdy426

Posted September 24, 2006 - 11:43 AM


Has the bike just recently lost it's low end or have you always thought it was weak?

That was going to be my question, too. If it's recent, check compression. You may need rings. If your riding style is changing such that you want more low end than stock, you have a couple of options...Big Bore gives more all over, and the heavier rotating mass from the bigger piston slows down the rev a little, giving the feel of more low end. Higher compression also gives you more all over, but you will likely have to run race gas. On an 02, you can try running WR cam timing (unless you've put the 03 cam in). In general, that gives you more down low, less on top, and less of a hit in the midrange. Most of us WR owners, except those who ride in woods and such, prefer YZ timing to get the midrange hit, though. Changing timing is, however, a freebie. Flywheel weights, or a WR ignition (flywheel and stator) will also slow down the rev, giving the feeling of more low end and less hit. Hot cams stage 1 cams for the YZ/WR offer a pretty good solution for powerband. The low end is very similar to a stock WR (that is, more than a YZ!), with a mid range hit and top end similar to a YZ. That kinda begs the question...do you really want more low end, or do you want a smoother powerband? If you want the latter, go with the WR timing or the flywheel weight. If you want more low end with the YZ-like midrange hit and top end, go with hot cams. The high comp piston and/or big bore kit compliments either approach nicely (it is, after all, only money, and you can't take it with you!)

My WR has the big bore kit, 13.5:1 Wiseco piston, hot cams, some port work, and a few intake and exhaust mods. The power is fantastic. It pulls like a tractor from zero to about 1/4 throttle. At qtr throttle, it has a pretty good hit, then revs out with pretty significant power all the way up. The hit is not quite as drastic as a stock YZ, but the power is head and shoulders above. It really is an impressive, easy to ride motor. It will easily pull two gears too high in just about any situation. Which is good, because I'm getting old, slow and lazy!

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