cam shaft lobe discoloration

4 replies to this topic
  • falshh

Posted November 22, 2005 - 07:43 PM


I noticed when checking my valve clearances at each side of the top of the cam lobe there is slight discoloration, a dark grey color, it doesnt look like its from heat.It looks like its just form opening and closing the valve.Bike runs great and valves were in spec, just curious if this is normal?

  • DigilubeJay

Posted November 23, 2005 - 05:01 AM


The solid lifters and the plain cam bearings are high contact areas. It is normal for there to be a slight change in the metalurgy of the contact surfaces, and thus a change in appearance of the metal.
If your valves are still within specifications, you probably are OK.

The design of a solid lifter and cam journal dictates that a robust lubricant be used.
The additives in the oils are what protect these items the most, and a cheapo oil that you have no idea who made, or what's in it, should never be used for such an advanced piece of equipment.

I know this goes against conventional wisdom...but try to use an oil with at least 40wt and contains moly. Moly is one of the best protectors of the solid lifters and cam journals there is. And it will not comprimize your wet clutch, as many will tell you it does.
Diesel oils are some of the best choices we can make. Very robust bases, with loads of additives, and at reasonable prices. (Rotella T, Delvac 1300, etc....)

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  • ripntear

Posted November 23, 2005 - 05:14 AM


I'm a Rotella 15w40 user. Not the best smelling stuff, but it's inexpensive and keeps things lubed and clean.

  • Diode663

Posted November 23, 2005 - 11:24 AM


I always thought moly made the clutch slip. Ohh well will have to give rotella T a try. Diesel oils are with out a doubt the most heavy duty. The only thing that concerns me is it too thick for winter?

  • grayracer513

Posted November 23, 2005 - 02:52 PM


See if this sounds familiar. The nose of the cam lobe is bright all the way across, but just behind that, the bright part narrows as you move toward the base of the lobe. The wear pattern is somewhat hourglass shaped, with a duller area on either side where it is narrowest, and widens back out as you move down the lobe. Sound like yours? That's a fairly normal wear pattern, and it gets put there partially by the fact that the cam sits very slightly off center over the lifter, so that it rotates under the cam as it works. That helps the lifter wear evenly, and avoids the grooving you find in engines with rocker arms that run on the cam. If this pattern is very biased to one side, your lifter may be dished (worn slightly concaved). If the cam has no trace of such a pattern, it might just mean that it has almost no wear on it at all, but look at the lifter face. If it has a "stripe" worn in it in line with, and the same width as the cam, that's no good, and usually means the lifter and cam should be replaced.

Moly is not the culprit. Depending on how it's used, it can be either a friction reducer or a boundary lubricant (an additive used to prevent metal-to-metal contact in the event of oil film failure from high contact pressure). A number of high grade motorcycle oils, such as Mobil1 MX4T, contain a fair amount of it. The warning in your manual is against using oils labeled API "Energy Conserving II". These oils, according to Yamaha "could cause" clutch problems. It doesn't say that they will for certain, but it's a good idea to avoid ECII oils unless you know of someone who uses a particular one successfully, or you're willing to experiment. There are enough good non ECII oils around that you don't need to take the chance with them.

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