yfz450 camshaft seize


18 replies to this topic
  • DIRTTRACKER0

Posted October 08, 2007 - 07:44 AM

#1

i have a 2003 yfz450 that the cams have seized in the head. the cam journals, camshafts are all scored. one journal is scored enough that the bucket will not come out. will i have to replace the head or does anyone know if someone can rework the journals on the head??

  • grayracer513

Posted October 08, 2007 - 07:56 AM

#2

Send your head to Engine Dynamics. They can fix it.

  • todds924

Posted October 08, 2007 - 09:00 AM

#3

I would get a NEW head if all that is damaged.

  • grayracer513

Posted October 08, 2007 - 10:10 AM

#4

A new bare head retails for $560. EDCo can (and has many times) rebore the cam bores good as new for much less than that.

  • todds924

Posted October 08, 2007 - 11:36 AM

#5

A new bare head retails for $560. EDCo can (and has many times) rebore the cam bores good as new for much less than that.


You mean they can put the "lost material" back and re-bore? I have seen YZ heads where a cam has seized and the buckets were stuck in the head. It took some fine grinding just to get the buckets out. Needless to say, the head needed new cams because of the galling, new buckets from the seizing, and a new head. It would probably depend on how severe the damage is as to what a machine shop could repair wouldn't you agree? I am not sure but I think you can buy a "complete" head from Yamaha. I know they were sending complete heads for the 250F when they had that little valve recall thing on blown up motors. Also i would assume the camshaft caps would be galled also and i don't know if that could be fixed. You can only get the camshaft caps with a new head- they are machined together right?

  • grayracer513

Posted October 08, 2007 - 12:38 PM

#6

The process is simple, really. First. about .002" (depending on how bad the damage is) is removed from the mating faces of both the cam caps and the head, then the caps are torqued in place, and the camshaft bore rebored .002" lower than it originally was. The reboring also cleans up the tops of the lifter bores at the same time. Good as new, really. If not, there are a lot of YZF's running around with repaired heads that don't know any better.

The only head available from Yamaha includes the cam caps, for the reason you stated, and the valve guides, and very little else.

  • todds924

Posted October 08, 2007 - 01:41 PM

#7

The process is simple, really. First. about .002" (depending on how bad the damage is) is removed from the mating faces of both the cam caps and the head, then the caps are torqued in place, and the camshaft bore rebored .002" lower than it originally was. The reboring also cleans up the tops of the lifter bores at the same time. Good as new, really. If not, there are a lot of YZF's running around with repaired heads that don't know any better.

The only head available from Yamaha includes the cam caps, for the reason you stated, and the valve guides, and very little else.


Very good information!!: I can see it all crystal clear now. The only question would be how damaged the head is. Also, those 250f heads Yamaha sent were complete with cams/shimmed and ready to bolt on.

  • grayracer513

Posted October 08, 2007 - 02:54 PM

#8

... those 250f heads Yamaha sent were complete with cams/shimmed and ready to bolt on.

If you're talking about the ones sent to replace those damaged by the defective valves in their recall on the '06, that's a whole different situation. Such a part would be worth $1200 easily.

  • todds924

Posted October 08, 2007 - 05:29 PM

#9

If you're talking about the ones sent to replace those damaged by the defective valves in their recall on the '06, that's a whole different situation. Such a part would be worth $1200 easily.


That is what i'm talking about exactly..$650 dealer. So yeah, easily $1200. I take it you have had good experiences with the machine shop in question? Engine Dynamics?

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  • grayracer513

Posted October 08, 2007 - 07:53 PM

#10

Not personally, but it comes with the recommendation of many, many TT'ers who have had this problem.

  • DIRTTRACKER0

Posted October 08, 2007 - 10:19 PM

#11

thank you for the very valuble info. it was exactly what i was looking for. another question if i were to purchase a head from ebay or another individual what years will fit the 03? will the quad head work also? i heard the cams are different from some years to another is this true. i did a search but came up incomplete. thanks again i love TT forums

  • grayracer513

Posted October 09, 2007 - 06:09 AM

#12

The '03-'05 heads will fit. Later heads have an internal oil feed, and won't work.

The '03-4 YZF head and the '04 YFZ quad head are the same. The '05 YZF head was different, and had a redesign of the intake ports. Yamaha says it will produce more top end power.

The '05 quad head is different than the others, but I'm not sure exactly how. The '05-6 WR head would probably work, but it's set up for air injection. I would avoid these last two.

  • todds924

Posted October 09, 2007 - 06:20 PM

#13

Not personally, but it comes with the recommendation of many, many TT'ers who have had this problem.


I was looking at a bare WR 450 head today and pictured the procedure. There isn't really much room from the cam bores to where the buckets stick up. I guess it would work if the galling wasn't to deep. Shimming those valves would take an awfull thin shim. I don't know. That seems like a cheap alternative to buying a complete head. I have only actually seen one trashed head like that because as you know they are pretty bulletproof. I did notice a weird "swirl" pattern on the top of the right exhaust bucket? This is from the decompressor? The WR is an 03. Kinda looks like a chatter wear ring.

  • grayracer513

Posted October 09, 2007 - 08:45 PM

#14

Shimming those valves would take an awfull thin shim.

If .002" cleaned up the bore, you would go down one shim size.

I did notice a weird "swirl" pattern on the top of the right exhaust bucket? This is from the decompressor? The WR is an 03. Kinda looks like a chatter wear ring.

Could be, see if it appears just outside the pattern created by the cam lobe.

  • todds924

Posted October 11, 2007 - 05:29 PM

#15

If .002" cleaned up the bore, you would go down one shim size.

Could be, see if it appears just outside the pattern created by the cam lobe.


That swirl mark is from the decompressor. . This motor has over 400 hours on it.

  • btray

Posted October 11, 2007 - 06:09 PM

#16

Can I jump in here and ask what causes this kind of break down in the first place. Oil pump failure or someone didnt check the valves early enough?

Bill

  • DIRTTRACKER0

Posted October 11, 2007 - 09:22 PM

#17

bttray beat me to it. what would cause this failure? i just put a new crank ass'y, piston reassembled everything went fine. bike fired right up ran, idled good, approx (4-5 min) bleed cooling sytem, could not test ride (4am) shut it down. went back next day started fine ran at idle for about 2-3 minutes and locked right up. yes i did have oil in it and follwed the manual to a "T" oiled camshafted, torqued all bolts etc. maybe i caused this challenge?? just to add when the cases were split i cleaned everything spotless, including oil pump screen, soaked everything in the bottom with oil before reassembly. what i dont want is to repair/replace head and cams and have same failure??

  • grayracer513

Posted October 12, 2007 - 06:33 AM

#18

The root of the problem is that Yamaha runs very tight clearances in these bores (.0011-.0024"). As a result, anything that goes wrong has the potential to cause trouble.

Sometimes it's the user's fault for incorrectly torquing the cam caps. Low oil pressure, dirty or broken down oil can also cause it. Whenever this happens, a certain amount of inspection is indicated, to be sure.

  • team510

Posted October 12, 2007 - 02:03 PM

#19

he he he. the cylinder head for my yz250 is $125 bucks brand new. =) sorry i couldnt resist.





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