Cam lobe wear?

[chitown]

Not sure if this belongs in Tech... Haven't been here in forever but nobody deleted the account

2015 FJ-09, 21,200 miles. Doing first valve check a bit early due to other owner reports and time to work on it due to covid. Bike runs well. 

intake all well in spec. Exhaust all tight and out of spec, some pretty far. More concerning to my untrained eye tho is that most of the exhaust cam lobes show shiny areas like the below pic. Does anybody know if there's a surface treatment I've worn off vs something more cosmetic/normal etc? 

The shop manual mentions inspecting the camshaft for "blue discloration/pitting/scratches" but not sure if what I have is a match for that or not. Checking and adjusting valves is about the extreme of my mechanical knowledge if that wasn't obvious already and the half dozen bikes I've done before haven't had anything of this sort.

Notice a new camshaft is $120ish from partzilla and the like but don't have the experience to know if that's treating problem vs symptom.

Bike is ridden hard but maintained well. Have a YES warranty that is due to expire in a bit but don't know if that would just be getting into a fight that might not be a huge issue. The bike's been reflashed, block offs etc no idea if I might get push back there. Don't even know if it would be considered a qualifying issue or "normal" wear and tear. 

What sayeth the interwebz?

 

Edited September 3, 2020 by chitown

[Lone Wolf]

23 minutes ago, chitown said:

Exhaust all tight and out of spec, some pretty far.

How tight? What are the numbers?

[chitown]

In mm: .13 .24 .14 .13 .14 .20

 

 

[koth442]

Could you take a couple more pictures please? I *think* I see what might be wear, but could also be odd reflections. 

[chitown]

Will try to get some more pics, gotta pull the exhaust cam regardless so will do so then. The shiny bits aren''t reflections. It's in a few spots on every lobe, intake as well as exhaust, to a varying degree. Intake are all in spec .14 - .16 mm.

 

[skipperT]

@chitown Your measured clearance numbers are typical - also note that the exhaust spec is much tighter than the intake - I believe the spec (converted) is 4-8 thousandths IN and only 10-12 thou EX (.26-.30 mm maybe?). It’s been a bit....

The shiny spots you have observed are also typical wear. Remember that the cam lobe has to contact the lifter when pushing the valve open and some wear occurs at that very spot. No amount of oil film will totally eliminate that contact. I’ve seen some EX camshafts on the CP3 engine wear a bit more than yours, where a SECOND “wear” pattern begins to develop WITHIN the “shiny” spot. That IMHO is when I would become concerned. A visible wear mark might also begin to become visible on the corresponding surface of the lifter at that point too.  If you can feel a distinct edge developing around the wear mark (not smooth) then that would be concerning as well.

i hate the vagueness sometimes of the Yamaha service manuals; going the extra mile and saying exactly what you should be looking for would make their instructions a bit more clear IMHO. That said, you can always measure the cam lobes with a quality micrometer and see if it falls outside the allowable spec, but in my experience (from the ones I’ve measured) they are usually very close to the limit, so close that I question my measuring technique and the mic that I’m using. Esp when trying to measure exactly where you see the visible  wear. You’d need to purchase a mic that equals or exceeds the number of decimal points in Yamaha’s published spec, which will probably be around the cost of a new cam!

i would just record the numbers for my own personal reference and consult it after another 20k to see if it’s gotten worse. Pics to jog your memory on your phone might be good too....

“loosen your clearances as close to 12thou as possible and run it”, would be my advice.

(sorry for all the “where” and “wear” usage, jeez...)

-Skip

Edited September 4, 2020 by skipperT