2010 YZ450 Head Damage


23 replies to this topic
  • BBrown626

Posted August 14, 2011 - 07:50 PM

#1

I have probably 80 hours on my bike.
Today I warmed it up and went riding. After about 2 minutes of riding I heard something unusual and pulled off the track. There was a metallic(?) sound from the top end and no oil flow in the sight glass. I shut it down and brought it home. I drained the oil to verify my level and check for any debris. Only 400 ml came out!
Clearly I have been neglecting looking at the oil flow before riding or this wouldn't have happened. :eek::bonk::smirk::bonk:I don't know how many hours it took to lose 600ml of oil.
I haven't noticed any oil in the exhaust nor have I seen any dripping out the valve cover vent. There are no external leaks, so it must be going out the exhaust or the vent while riding.
I took out the cams and pulled the head for inspection. The camshaft journals have light scoring, as do the camshaft cap journals. Nothing real rough, but not normal. I'd guess they are scored to the depth of a phonograph/record.
The lobes and buckets look great. I don't feel anything unusual in the bearings nor do I see discoloration anywhere. The combustion area and the top of the piston have a lot of carbon on them and it is crusty rather than sooty.
The manual does not address damage to the cam caps or journals. How much damage is acceptable to the camshaft journals or caps? Can they be polished or otherwise repaired at a cost less than replacement?


Thank you.

  • grayracer513

Posted August 14, 2011 - 08:56 PM

#2

The manual calls for a maximum clearance at the camshaft of .003" (0.8mm). The first step would be to hone the cam bores smooth, polish the cams, and then check the clearance with Plasti-Gage. If the clearance is excessive, or the scoring of the caps too deep to hone out to a satisfactory degree, the head can be "line bored".

Line boring is a process that begins by setting the head up in a mill and shaving as little as possible, often .002" or less, from the surface the caps bolt to. Then the caps are also shaved and bolted into place on the head. The cam bores at this point are both out of round and under size. The final step is to recut the bores in the head to their correct size.

Engine Dynamics does a great job of this for much less than the cost of a head.

  • BBrown626

Posted August 15, 2011 - 02:56 AM

#3

The manual calls for a maximum clearance at the camshaft of .003" (0.8mm). The first step would be to hone the cam bores smooth, polish the cams, and then check the clearance with Plasti-Gage. If the clearance is excessive, or the scoring of the caps too deep to hone out to a satisfactory degree, the head can be "line bored".

Line boring is a process that begins by setting the head up in a mill and shaving as little as possible, often .002" or less, from the surface the caps bolt to. Then the caps are also shaved and bolted into place on the head. The cam bores at this point are both out of round and under size. The final step is to recut the bores in the head to their correct size.

Engine Dynamics does a great job of this for much less than the cost of a head.


Thanks. I am going to look them up.
The scoring is probably not the depth of a phonograph. I can feel them with a fingernail, but the nail doesn't catch on them. Maybe it can be saved.

  • grayracer513

Posted August 15, 2011 - 06:31 AM

#4

You may be able to clean things up by lapping the cams to the head and caps if it's not too bad. Because this involves abrasives, it's a good idea to have the head off the engine so it can be cleaned up.

  • jcm3

Posted August 15, 2011 - 11:17 AM

#5

Clearly I have been neglecting looking at the oil flow before riding or this wouldn't have happened. :eek::bonk::smirk::bonk:I don't know how many hours it took to lose 600ml of oil.


Ouch, I hope it works out well for you and doesn't cost you much.

It's a good lesson for the rest of us to be diligent about it.

  • BBrown626

Posted August 15, 2011 - 03:51 PM

#6

Ouch, I hope it works out well for you and doesn't cost you much.

It's a good lesson for the rest of us to be diligent about it.


Very price lesson.

A local shop (Pro-Tec) thinks they can fix in in an hour or two. Engine Dynamics quoted $270 to repair the head and see what they could do with the cams.
The cams are some hard metal though, so I may avoid the risk and replace them. I'll see what the experts say.

  • crf450319

Posted August 15, 2011 - 08:26 PM

#7

Man that sucks ! I'm just curious, not trying to insinuate that you don't change your oil often enough or place blame.. but I'd like to know how ofter you do change your oil ? The reason being, I change the oil in my '09 every 7 hours and I think I've checked the level 4 or 5 times in 104 hours of runtime.

I just assume that because I change it that often, I'd notice any significant loss.. But after reading this thread, maybe I wouldn't ?

  • CaptainKnobby

Posted August 17, 2011 - 05:57 AM

#8

I guess I change my oil to often. I dont think I give it time to lose any oil at 3 hour change intervals. Let us know the outcome and what you done to fix the problem.

  • crf450319

Posted August 17, 2011 - 07:46 AM

#9

I guess I change my oil to often.


I'd think that would depend on what oil you're running. If I was running Rotella, then I'd be on the same 3 hour schedule. I run a full synthetic motorcycle specific oil, and run it longer. It's 6 of one and a half dozen of another really.

  • SUnruh

Posted August 17, 2011 - 07:50 AM

#10

fyi, your "full synthetic motorcycle specific oil" probably isnt as good as you think it is.

get a test kit and send it off to blackstone labs and prove it! :eek:

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  • crf450319

Posted August 17, 2011 - 08:16 AM

#11

fyi, your "full synthetic motorcycle specific oil" probably isnt as good as you think it is.

get a test kit and send it off to blackstone labs and prove it! :eek:


Posted Image

By not naming the oil I'm running I was trying to avoid a 4 page, waste of time, my oil is the best ever post war. I choose to run a synthetic oil as opposed to a mineral based oil, I spend a little more on it and run it a little longer. I'm content with my choice, and really... that's all I care about. I don't need to prove anything, not that it wouldn't be nice to know..

  • BBrown626

Posted August 18, 2011 - 05:07 PM

#12

I change my oil at about 8 hours, which is usually 3 or 4 trips to the track.
It is Amsoil MCF

In this case i was probably at the 8 hour mark on hours.
Inspection revealed that the right side intake valve was coated with burnt oil and that valve was not fully closing. The valve looks great, but the seat was fouled. There was a lot of burnt oil on the head. The pic you see is after I cleaned the head with brake cleaner (no mechanical cleaning). Apparently the seals were leaking on the intake valves. I never detected the smell of burning oil. Maybe the synthetic stuff doesn't smell like burning dyno oil?

The guys at Pro-Tec think they can fix the head and cams with about 2 hours of labor. I am keeping my fingers crossed. A stock head and cams is about $890.

Intake cam and cap:
Posted Image

Head:
Posted Image

Intake Valve:
Posted Image

  • BBrown626

Posted August 18, 2011 - 05:14 PM

#13

Man that sucks ! I'm just curious, not trying to insinuate that you don't change your oil often enough or place blame.. but I'd like to know how ofter you do change your oil ? The reason being, I change the oil in my '09 every 7 hours and I think I've checked the level 4 or 5 times in 104 hours of runtime.

I just assume that because I change it that often, I'd notice any significant loss.. But after reading this thread, maybe I wouldn't ?


I've never noted a significant change in the amount of oil drained, but I haven't measured it in the past. Now I will measure the oil drained. That may help detect a problem earlier. The consumption rate has probably gone up over time and I didn't catch it early enough. The couple hundred bucks this is costing me would have bought a lot of oil.

  • BBrown626

Posted August 20, 2011 - 11:50 AM

#14

I investigated further and found more damage and probably my real trouble. The oil pump gear and the idler between the primary driven gear are damaged. There was a large chunk of some case metal lying below them. I haven't found the source of it yet, but it looks like the cogs on the sides of a tranny gear. The ballancer drive gear and the adjacent gear were a little chewed up. All the metal shavings explain the damage to the cams and head.

The worst part is that whatever broke the oil pump gear drove the idler up hard enough to brake the case. I don't know if it can be repaired or if I need a new set.

Broken oil pump gear and drive gear.
Posted Image

More work lies ahead.
Posted Image

Broken case.
Posted Image

  • grayracer513

Posted August 20, 2011 - 02:18 PM

#15

Pull both pumps out and have a look at the pocket where the return pump works.

  • Octanee

Posted August 20, 2011 - 03:08 PM

#16

Yikes!, you must have went a really long time or something with out checking oil? i run synthetic because its great stuff, man made and doesnt have the issues or downsides of mineral oil, so yeah ill go longer on a oil change depending on oil color,

but one should always check their oil level every ride or 2, because you never know, might be fine for a while then the valve seals or something goes crap and starts burning oil,

  • BBrown626

Posted August 20, 2011 - 03:51 PM

#17

Yikes!, you must have went a really long time or something with out checking oil? i run synthetic because its great stuff, man made and doesnt have the issues or downsides of mineral oil, so yeah ill go longer on a oil change depending on oil color,

but one should always check their oil level every ride or 2, because you never know, might be fine for a while then the valve seals or something goes crap and starts burning oil,


I don't think this had anything to do with the oil level, but I agree with your recommendation.

Once I get the flywheel off I'll be able to look at all the internals and figure out where the chunk came from and what damage was done in the transmission.

  • BBrown626

Posted August 20, 2011 - 03:52 PM

#18

Pull both pumps out and have a look at the pocket where the return pump works.


Do you think the case can be repaired?

  • grayracer513

Posted August 20, 2011 - 07:44 PM

#19

I haven't seen the damage to the case, but it sounds as if you say it's broken around the idler shaft bore. That can be tricky, but that sort of thing is quite repairable in most cases. Show it to a TIG welder/machinist. It has to come apart one way or other anyway, right?

  • BBrown626

Posted August 21, 2011 - 10:15 AM

#20

I haven't seen the damage to the case, but it sounds as if you say it's broken around the idler shaft bore. That can be tricky, but that sort of thing is quite repairable in most cases. Show it to a TIG welder/machinist. It has to come apart one way or other anyway, right?


The damage to the case is above the oil pump. I will definitely bring it to a shop and ask if it can be fixed. $550 for cases. Anything significantly less with properly alignment of the shaft is a bargain.

Suppose I need to replace the case, do you think any bearings are reusable or will extraction cause damage?

Posted Image





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