08 YZ450F Gearing


12 replies to this topic
  • roylo

Posted May 12, 2009 - 12:40 AM

#1

Hi this is my first post here and Ive just bought a near new 08 YZ450F with a Pro Circut T1 Muffler as the only modification.

The gearing is standard 13/49 and the bike goes ok in general but the chain chatters annoyingly down low until the revs rise. The chain IS adjusted correctly. This is my first 450 after coming off a 250 2stroke and to me the gearing feels way too tall compared to my old bike.
Does any of this seem normal for this bike?

Thanks for any help guys..

  • grayracer513

Posted May 12, 2009 - 05:16 AM

#2

It is geared taller than your 2-stroke was, and it fires half as often and twice as hard. With the extremely low rotating mass (for a big 4-stroke), the engine can't spin at a steady speed when moving slow under a load, which is where the chain slap at low RPM comes from. That's all normal.

Double check the chain adjustment, though, because once it really is set according to the manual, it "looks" loose to just about everyone. But setting it any tighter than specified causes it to draw tight at mid swing, and risks breaking the rear hub. With the bike on a stand, wheels off the ground, there must be at least 1.9" (48mm) between the rear bolt holding the chain slider and the bottom of the chain as you pull up on it.

Have a manual for it? http://www.yamaha-mo...ice/manuals.jsp

As to whether it's geared "too high", that kind of depends on how you ride it.

  • Wiz636

Posted May 12, 2009 - 06:01 AM

#3

Also the stock chain is a flimsy POS and will slap aroud more than a good quality o-ring chain. Get rid of the stocker before it eats your sprockets.

  • BlackT5

Posted May 12, 2009 - 07:02 AM

#4

I went up 2 teeth on the rear. On the tight stuff its nice on the flat it is over geared. I also bought a 1 tooth up to try and it may be a good compromise. I am a novice rider and like the 2 up. Gets the motor up a running and I am not going faster than my skill can keep up. Rear sprockets are cheap so I recomend that you play around and find what you like.

  • roylo

Posted May 12, 2009 - 06:07 PM

#5

It is geared taller than your 2-stroke was, and it fires half as often and twice as hard. With the extremely low rotating mass (for a big 4-stroke), the engine can't spin at a steady speed when moving slow under a load, which is where the chain slap at low RPM comes from. That's all normal.

Double check the chain adjustment, though, because once it really is set according to the manual, it "looks" loose to just about everyone. But setting it any tighter than specified causes it to draw tight at mid swing, and risks breaking the rear hub. With the bike on a stand, wheels off the ground, there must be at least 1.9" (48mm) between the rear bolt holding the chain slider and the bottom of the chain as you pull up on it.

Have a manual for it? http://www.yamaha-mo...ice/manuals.jsp

.



I not 100% sure the sound Im hearing is the chain slapping or the engine but its a chattering/knocking sound from the left side only, down very low in the rev range. When looking at the chain the sound seems to follow the shacking of the chain. Im just not used to a four stroke yet so I dont know but hopefully it is just the chain like you guys say. And yes the chain is within 48mm- 58mm and it does look too loose to most people but that is how it is supposed to be.
How can I stop the chain making this noise anyway because its annoying me.

First gear on my 2 stroker was great for very slow technical steep hills out in the bush. The 450 in first gear is way too tall for this.

  • goodriddance

Posted May 12, 2009 - 06:27 PM

#6

I ride really tight stuff most of the time and found the gearing to tall also, I dropped the front down 1 tooth and never looked back, like said the stock chain is a POS ditch it for a O-ring as soon as you can and you wont hear the chain slap anymore

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  • grayracer513

Posted May 12, 2009 - 06:43 PM

#7

How can I stop the chain making this noise anyway because its annoying me.

Go faster in a lower gear. Keep the revs up a bit. That's the only way other than trying to figure out how you might add 3 pounds to the crank.

First gear on my 2 stroker was great for very slow technical steep hills out in the bush. The 450 in first gear is way too tall for this.

  • Learn to use the clutch, or
  • Gear it way down and give up your top end, or
  • Install a WR trans gear set, or
  • Install a Rekluse auto clutch


  • tmoney302

Posted May 24, 2009 - 11:17 PM

#8

I put a 9 ounce heavier steahly flywheel on my 08 450 and it got rid of the chain slap and made it alot easier to run low on the pipe in the tight stuff.

  • green flash

Posted May 25, 2009 - 02:57 AM

#9

yep, the stock chain isn't so good.

  • hyperflow

Posted May 25, 2009 - 01:47 PM

#10

I run 13-51, I lost 1 bike lenght in a drag race going down to 13-50. 13-51 seams to be the best gearing for my bike anyways.

  • MATTH530

Posted May 25, 2009 - 05:28 PM

#11

Chain slap is going to happen on a 4 stroke!!! On my 07 and 08 even with a TM desing guide and slider and 14 52 gear is it still is there............
Matt

  • NortonMoto

Posted May 25, 2009 - 07:16 PM

#12

I Change to 13-51 And it sames perfect for me,80% tight trails 20% track I'm also A big guy at 230lbs.

  • dogg502

Posted May 27, 2009 - 12:42 PM

#13

I have a 08 yz 450 and I thought the same thing when I first rode it, between the chain slapping and the valve train noise I was a little freaked out but you will get used to it. I put 13/48 gears on my bike with fmf 4.1 slip-on the thing feels great!





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