Exhaust cam bucket damage?

Hi guys,

I'm in the process of reshimming the valves and noticed the exhaust bucket that the autodecompression buttom hits has 8-10 dings in it. The center where the cam lobe rides is fine, so I don't think it will hurt anything. What have some of the rest of you seen. I've got about 500 miles on the bike.

Thanks,

Mike

Hmmm. Sounds like your decomp cable/lever system doesn't have enough slack in it, or didn't at one time.

I'm not 100% certain I'm understanding you correctly, but your bucket shouldn't have any visible dents like you are describing. :)

The dings were probably there from the beginning at the factory. The decomp button or cam lobe could not have caused that. :) Your valve clearances should be fine. I went 3000 non racing miles before having to reshim. :D

I'll get a picture of the bucket, the dings are in a circular pattern where the button would contact it. I've already got the cams out to reshim. All 5 were too tight. Intakes were 0.003, 0.002, and 0.003 (inches). Exhausts were 0.007. Didn't want to chance burning valves. FYI Hick - mine is an 03, auto decomp. One thing I saw that I didn't like was in the intake cam cap on the bearing surface opposite the gear (if that makes sense :))there is an indication that a metal shaving made a couple of rounds in there. Cam is fine, but there is a very small groove (barely can catch a fingernail) in the cap that lines up with the oil hole on the outside edge. Any thoughts?

Thanks,

Mike

FYI Hick - mine is an 03, auto decomp.

Oops, I didn't see that.

Just make sure the oil passages are all clear.

If it were me I'd consider replacing that bucket, make sure to use some assembly lube if you do, and I'd double-check the auto-decomp clearance (if that applies).

Hope this helps.

:)

If I decide to replace the bucket, are there any clearance issues? (I've been reading RC3's troubles over on the YZ side.)

Mike

If I decide to replace the bucket, are there any clearance issues? Mike

W/ respect to the bucket bore? I dunno. It should easily rotate in the bore...

The valve clearance may be slightly different w/ the newer bucket but I doubt it...

:)

buckets are color coded for fittment.

There should be a reference colored dot on the inside of the head next to the bucket bore and one inside the bucket.

Light seizure marks are not unheard of on the cam journals.

Thanks for the info SFO. I recall seeing a colored dot inside the bucket now that you mention it. Nobody stocks buckets or shims, so I'm going to emory paper down the shims and put her back together so I can ride while I'm off for Christmas. I'll order up the bucket and replace at the next valve check. :)

Mike

Hi guys,

I'm in the process of reshimming the valves and noticed the exhaust bucket that the autodecompression buttom hits has 8-10 dings in it. The center where the cam lobe rides is fine, so I don't think it will hurt anything. What have some of the rest of you seen. I've got about 500 miles on the bike.

Thanks,

Mike

I have the Yz 450 cam mod on mine, the auto decomp has done the same to my bucket, very slight marks and not where the lobe runs so i think it's really a non issue, i have about 4500 K's with this camshaft, the more k's the more marks so i think a new bucket would be a waist of money.

Bumppity Bump!

Sorry to bring this subject up again, but I have the same symptom on my 04' WR450.

Im checking the valve clearance for the 1st time, with 1300miles on the clock. All valves are just outside of spec, on the tight side. All cam lobes and bearing surfaces look fine, and all buckets look fine except the one exhaust bucket where the auto decompression pin hits it.

Did we ever get a conclusion about these 'witness marks' on the bucket from the de-comp pin?? There is no way to avoid it, so it must be normal. But should the bucket be replaced periodically? What is the conclusion?

After all this time i stick to my previous reply, they all do it and a new bucket is a waist of money, it will just do it again !

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