Shim Bucket Help.


24 replies to this topic
  • taksx

Posted February 18, 2009 - 12:36 PM

#1

If one of my shim buckets has obvious wear showing should I replace that one only or should I pony up and replace all 5 of them for good insurance?

Thanks, Eddie

  • GCannon

Posted February 18, 2009 - 03:07 PM

#2

If the wear is on the face then I would be more worried about the cam lobe?


Can you describe the wear?

  • taksx

Posted February 19, 2009 - 08:54 AM

#3

I should take a picture and post it. It basicaly looks like the lobe vibrated on it or the bucket was spinning. minor groves is the end result.
the lobe is fine no dents or scratches. I'll just replace it for good measures.

Thanks for your help.

  • GCannon

Posted February 19, 2009 - 10:20 AM

#4

I belive the buckets are designed to spin so as to not concentrate the wear in one place. if it looks like discolored circles in the face of the bucket. If you cannot feel ridges with your fingernail then it may be normal.

Anyone else have anything to add?

  • Frostbite

Posted February 20, 2009 - 03:37 AM

#5

I should take a picture and post it. It basicaly looks like the lobe vibrated on it or the bucket was spinning. minor groves is the end result.
the lobe is fine no dents or scratches. I'll just replace it for good measures.

Thanks for your help.




Does it look like this?
Posted Image

The other 4 buckets are perfectly normal, this one looks like an artist was doing a bit of engraving.
I'm curious now that you have one bad one and so do I. Mine is the exhaust bucket near the cam chain. The cam lobe looks like new, not a mark.
Posted Image
It's as if the bucket was dented by something other than the lobe, maybe even before it was installed in the engine.

  • taksx

Posted February 20, 2009 - 08:58 AM

#6

Wow that looks bad! Sorry Frost.

Mine only has the center groves, and its the same valve as yours :lol:. The lobe on the other hand is picture perfect not a mark on it.

I was told it could be that the head is starting to go bad?
But that particular valve was on the tight side of the specified clearance. I'm blaming that to be the culprit. I'm buying a new bucket and keeping my eye on it for the next few rides.
FYI that bucket or lifter sells for $42 U.S Dollars.

P.S good pics thanks for posting them.

Eddie

  • brad the best

Posted February 20, 2009 - 12:40 PM

#7

its just were the auto decomp pin hits the bucket , mine looks the exact same i wouldn't worry about it unless its in the actual path of the camshaft .

if the lobe and the path the lobe takes is fine don't worry about it .

not that it hurts to buy a new bucket , just i have been running mine like that for uhm how long have i had my bike 2-3 years . it was like that first time i took the valve cover off and still is , runs like a champ .

  • taksx

Posted March 02, 2009 - 09:37 PM

#8

I got the lifter (bucket) in the mail and snapped this picture of the old and new. Now that I look at it I think this is worse then Frost's. Here is the end result.

Posted Image

Anybody else with the same issue? this is the exhaust lifter next to the cam chain.

Eddie :p

  • Alternative

Posted March 02, 2009 - 09:57 PM

#9

I'm thinking lack of oil could cause something like that. Check the oil way going to the cam cover is clear, maybe there's a flaw in the casting blocking the hole slightly. Just speculation.

  • matt4x4

Posted March 03, 2009 - 05:12 AM

#10

Definitely NOT the cam lobe that did that damage - but yes - I'd be tempted to say it's the auto decomp that is causing it.

Most likely what is happening is:
Auto decomp comes into play under 1300 rpm, if your idle is lower than 1300 rpm, then every time you idle your bike, the auto decomp is hammering the bucket, making it look like that over the long haul.

At least you know your bucket is spinning freely!

Turn your idle up a little.

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  • Frostbite

Posted March 05, 2009 - 02:53 AM

#11

Definitely NOT the cam lobe that did that damage - but yes - I'd be tempted to say it's the auto decomp that is causing it.

Most likely what is happening is:
Auto decomp comes into play under 1300 rpm, if your idle is lower than 1300 rpm, then every time you idle your bike, the auto decomp is hammering the bucket, making it look like that over the long haul.

At least you know your bucket is spinning freely!

Turn your idle up a little.


That makes sense to me, I tend to keep my idle low. Thanks Matt. :p

  • William1

Posted March 05, 2009 - 06:39 AM

#12

I keep my idle set to between 1,800 and 1,900 rpm.

  • taksx

Posted March 05, 2009 - 09:32 AM

#13

Thanks for the tips guy's I'm going to try it too.

  • grayracer513

Posted March 05, 2009 - 10:19 AM

#14

this is the exhaust lifter next to the cam chain.

I'm curious. Did you perhaps either retime your stock cam and grind the pin to compensate? Have you installed an after market cam?

  • taksx

Posted March 05, 2009 - 10:23 AM

#15

I'm curious. Did you perhaps either retime your stock cam and grind the pin to compensate? Have you installed an after market cam?


No its all stock in there. I don't like to fool with after market stuff on my engines.

  • grayracer513

Posted March 05, 2009 - 10:27 AM

#16

Auto decomp comes into play under 1300 rpm,

The auto decompression unit activates at around 700-800 crank RPM, not 1300. It's actually possible to kick the engine too fast and cause the unit to swing out, making it hard to start. The unit should never be in effect at any realistic idle speed.

One thing at play here it that on WR's up to about '05 or '06, the camshaft itself it actually the same as used in an '03-'05 YZ450. But, because the cam is advanced relative to the YZ, a longer decomp pin is used. Because the pin is longer, it contacts the lifter at a more acute angle and under greater peak pressure. This may bear on the difference in wear between the two engines at this point.

  • matt4x4

Posted March 06, 2009 - 04:45 AM

#17

I got the 1300 straight off a yamaha write up - either way - too low of an idle and it can start hammering away.

http://www.motorcycl...maha2003mx.html

  • grayracer513

Posted March 06, 2009 - 07:35 AM

#18

I got the 1300 straight off a yamaha write up

The source of that was Motorcycle Daily, not Yamaha.

  • matt4x4

Posted March 06, 2009 - 07:43 AM

#19

"a yamaha writeup" - not "Yamaha's writeup" - the bike they wrote up about IS blue and their source was supposedly Yamaha as they stated.

  • brad the best

Posted March 06, 2009 - 09:26 AM

#20

I got the lifter (bucket) in the mail and snapped this picture of the old and new. Now that I look at it I think this is worse then Frost's. Here is the end result.

Posted Image

Anybody else with the same issue? this is the exhaust lifter next to the cam chain.

Eddie :p


ya i have the exact same issue its just the decomp pin hitting the bucket , don't worry about it . mine has been doing it since 2003 i have never replaced the bucket its fine .

mine isn't dented as bad as your though . not a bad idea to replace that bucket yours actually looked pretty dam rough .




 
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