2010 YZ Issue

7 replies to this topic
  • smee23

Posted June 28, 2010 - 06:17 AM


When I release the clutch in nuetral the motor gets reall noisy, if I pull the clutch lever in it quiets down. I am not sure what is causing the noise but I don't remeber it before, has anyone else had this problem ?

  • blakers213

Posted June 28, 2010 - 06:57 AM


My new 2009 yz450f with one and a half hours on it does the same this. Not real noisy just I hear a noise. So probably nothing to wdorry about.

  • eazrider

Posted June 28, 2010 - 07:46 AM


Virtually every motorcycle in the world with a manual clutch does that. letting the lever out in neutral allows all the "loose" clearances in your clutch to rattle a bit, squeezing the lever loads all the components and quietens them.....ride it....:banana::)

  • grayracer513

Posted June 28, 2010 - 08:29 AM


It has to do with the fact that the engine does not run at a steady speed at an idle, but is slowed abruptly by each compression stroke, then accelerated vigorously by the following power stroke, "rattling" the gear box:


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  • smee23

Posted June 28, 2010 - 08:36 AM


Sounds good I will just ride it if this is normal, I wonder if a different weight oil might quiet it down ?

  • grayracer513

Posted June 28, 2010 - 08:45 AM


You can do that, but your first concern with oil viscosity should focus on how well it lubricates. Using an excessively viscous oil slows circulation in the system, which can be far more harmful than an oil that is a little too thin.

  • rickallen124

Posted June 28, 2010 - 10:29 AM


Gray, what is excessively viscous oil? I usually run Maxima extra 15w-50 during the hot summer months.

Edited by rickallen124, June 28, 2010 - 11:00 AM.

  • grayracer513

Posted June 28, 2010 - 11:19 AM


A 20w-50 is unnecessarily thick when temps don't rise over 90, IMO. There's probably no risk in running it until the ambient temps are below 70 all the time, and even then, it may not really become a problem. It is a question of at what point the benefits of a faster circulating oil feed outweigh the benefits of a thicker oil.

Oil viscosity is one element of the strength of the oil film. Engines with almost all plain bearing surfaces spread their bearing loads over broader areas than ball/roller bearings do, and are benefited much more by a greater volume of oil delivered at all times than they are by a thicker oil. Conversely, heavily loaded ball and roller bearings tend to put greater "point pressure" on the bearing raceways, are are more dependent on the integrity of the oil film itself.

Most automotive engines get along just fine on 30wt or even lighter oils, but the rolling bearings of the crank ask for more. Still, our engines are a mix of plain and rolling element bearings, so you need to consider and balance both needs. To that end, I use a 10w-40 most of the time, and then when it starts to stay over 90-95 most of the time (July-Sept around here), I switch to a 20w-50.

I think it actually depends more on how you ride than on the weather, although both are factors. If you do a lot of low speed, clutch slipping, canyon crawling in 80 degree weather, you might need a 20w-50 more than a guy racing MX in 98 degree heat does.

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