New to me 03 Yz 450 (rebuild)


108 replies to this topic
  • BDubb106

Posted May 09, 2012 - 04:23 AM


two pics I snapped yesterday when I was checking things out. Forgot I took them, musta been the Bud Light. Dont really know why I took em but here ya go.

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  • BDubb106

Posted May 24, 2012 - 08:37 AM


well finally got around to tearing the bike down to inspect the timing chain since the bike kept skipping time, went ahead and bought a new chain and this is what I found.

Doesnt look too good for a "new" chain. No way this chain should be this stiff and kinked since the bike only has about 30 mins on it since the rebuild. I never really paid much attention to the chain since it was supposed to be new which was a knucklehead move on my part, when I tore it down I inspected everything but the chain.

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It was actually stiff enough that I could not move a few of the links by hand. Whats the deal with this, do you think they actually replaced the chain or just kept the old one in there? I dont understand why you wouldnt replace a $30 chain when you already had the whole top end apart.

Edited by BDubb106, May 24, 2012 - 08:37 AM.


  • grayracer513

Posted May 24, 2012 - 09:06 AM


For one thing, the chain's only $20 retail. As to the question of whether that was replaced: Uh, no. That's one of the worst ones I can remember seeing. The only chance of it having been new is if it was run for the claimed 30 minutes and then shut down for two years and had rust set in. Any signs of that?

Chains with even one or two tight links can "fool" the tensioner by not letting it tighten down on the chain correctly. Then, when the revs come up and a couple of the links snap back straight, it's loose all of a sudden and will jump somewhere between the intake cam forward to the crank. It's even more likely if the engine ever kicks back or bounces back off compression as it stops.

  • BDubb106

Posted May 24, 2012 - 10:43 AM


For one thing, the chain's only $20 retail. As to the question of whether that was replaced: Uh, no. That's one of the worst ones I can remember seeing. The only chance of it having been new is if it was run for the claimed 30 minutes and then shut down for two years and had rust set in. Any signs of that?

Chains with even one or two tight links can "fool" the tensioner by not letting it tighten dowmn on the chain correctly. Then, when the revs come up and a couple of the links snap back straight, it's loose all of a sudden and will jump somewhere between the intake cam forward to the crank. It's even more likely if the engine ever kicks back or bounces back off compression as it stops.


The one I got from the dealer was $28 but thats not the issue. I could care less about the $8 mark up. I guess what your trying to say is I got screwed over yet again by the shop... thats what my issue with dealers is, they are too lazy to double check their work. Kind of like my R1 that I had serviced and tires changed and they conveniently forgot to put oil back in after they drained it. I go to pick it up and pull onto the street only to realize my engine light is on. :cry: How do you not notice these things when a customer pays $68 an hour to have their stuff done by a (and I use this term lightly) "real mechanic"? Its shameful really.

You answered my question to the issue, IDK how they could say they replaced it when it looks like that. Its the first time Ive ever seen one up close (first time Ive ever been totally inside a 4 stroke motor) and I knew immediately what the issue was. Theres no way that chain wasnt bad when they tore the motor apart and after 30 mins it looks like that. That was my real question as to whether it is possible to get a "bad chain" that could kink up like that if it had been sitting on the shelf for years or something? I got the 30 min # because that is the amount of time I have put on the bike since it was torn down by said shop and my hour meter proves it. I didnt see any rust on or in the chain but wasnt really looking for any either, Ill go take a look to see. Ill post up some better pics of the chain when I do and maybe you can take a look to see if there is anything abnormal about it since I have never even put my hands on one before. I actually had the chain "replaced" when I had the bike looked at because they themselves recommended it and fresh piston and rings put in it because I was too nervous about tearing into it myself with no one to help for the first time. So I know for a fact the piston and cam chain should have had no more than the 30 mins run time on it and it only sat over the winter.
On a side note the piston and valves looked brand new with hardly any traces of discoloration or carbon build up on them yet. Rings showed zero signs of wear as well! Also none of the cam teeth or teeth on the crank showed any signs of wear from the chain.

What do you mean by the engine kicks back or bounces off the compression? Also what is the recommended time frame that these should be replaced so I dont run into this problem again?

Oh and thanks for all your help! Youve been extremely informative and patient with my lack of knowledge while I have been working the kinks (no pun intended) out of this bike. :cry:

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  • KJK_JR

Posted May 24, 2012 - 10:57 AM


Yikes thats scary! I change my cam chain once a season. So roughly 25-30hrs. Probably a bit overkill but Its worth it in the long run. Also, check that the auto chain tensioner is working properly.

Edited by KJK_JR, May 24, 2012 - 10:58 AM.


  • grayracer513

Posted May 24, 2012 - 10:57 AM


...thanks for all your help... while I have been working the kinks out of this bike. :cry:


OK, that was cute. :cry:

Kicking back is when the bike is being started and the ignition pushes the piston back down the bore before it goes over the top, causing the engine to reverse, sometimes quite vigorously, which makes the kick crank rise under your foot abruptly, ergo, "kicks back". "Bouncing back" occurs as the engine slows to a stop when shut off. The crank rotates forward and the piston comes up on the compression stroke with enough inertia to go part way up, but not over the top. Then the compressed air in the chamber pushes the piston back down. Both these cause the engine to rotate backward, which can straighten out several of the kinks you mentioned. Because the loaded side of the chain is against the tensioner under that circumstance, the slack that forms is not corrected as it rotates in reverse, and it will almost certainly skip time.

Your dealer sounds like the wrong place to get anything done. Marking MSRP up 25% is bad enough. Forgetting to add oil after draining is inexcusable. Anyone working for me would do that no more than once.

  • BDubb106

Posted May 24, 2012 - 11:14 AM


OK, that was cute. :cry:

Kicking back is when the bike is being started and the ignition pushes the piston back down the bore before it goes over the top, causing the engine to reverse, sometimes quite vigorously, which makes the kick crank rise under your foot abruptly, ergo, "kicks back". "Bouncing back" occurs as the engine slows to a stop when shut off. The crank rotates forward and the piston comes up on the compression stroke with enough inertia to go part way up, but not over the top. Then the compressed air in the chamber pushes the piston back down. Both these cause the engine to rotate backward, which can straighten out several of the kinks you mentioned. Because the loaded side of the chain is against the tensioner under that circumstance, the slack that forms is not corrected as it rotates in reverse, and it will almost certainly skip time.

Your dealer sounds like the wrong place to get anything done. Marking MSRP up 25% is bad enough. Forgetting to add oil after draining is inexcusable. Anyone working for me would do that no more than once.


Lol makes sense... I get it now.

Sad part is that it only takes once. If I wouldnt have looked down they would have had a hard time explaining why the motor blew in my $14,000 motorcycle after the first service.

Again, thanks for the help... fingers crossed that the new chain fixes the issue! Ill get those pics up asap. They are uploading to PB now.

  • BDubb106

Posted May 24, 2012 - 11:29 AM


I dont see any signs of rust or discoloration, I just dont think it was replaced. Its got about 8-10 rough spots in it that will kink when rotating the chain.
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  • sid_125_04

Posted June 03, 2013 - 06:11 PM


Update? You ever get this thing 100% like the yz250?





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