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Cam chain & tensioner

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I was checking my valve clearances the other day on my 06KX450F and noticed the cam chain seemed to have a little too much slack in it. How often do the tensioner/chain need to be replaced? I've got the tensioner in there tight, I'm assuming its the tensioner. How much "slack" is appropriate?

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I was checking my valve clearances the other day on my 06KX450F and noticed the cam chain seemed to have a little too much slack in it. How often do the tensioner/chain need to be replaced? I've got the tensioner in there tight, I'm assuming its the tensioner. How much "slack" is appropriate?

The tensioner should hold the chain taught on the tensioner side. Basically there should not be any slack. You can check to see if the tensioner is all the way extended by removing the center bolt and inserting the holding tool. Remove the tensioner assembly and measure the length extended. Then remove the holding tool and see if it extends any further. My guess is your tensioner has failed.

I replace my chain every time I rebuild, which is about every 50 hours.

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Thanks for the info. Not sure how many hours are on it, I've had it for a couple years but have ridden it fairly little. It wouldnt surprise me though since its an 06 and the tensioner/chain have never been replaced.

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I just replaced the cam chain and tensioner on my 2009 KX450, total cost for the parts was $150, $22 for a flywheel puller and $15 for a PDF service manual off Ebay. IMO the tensioner can be the "ticking time bomb" in modern 4 strokes and, like others have said, the chain does stretch over time. Even on my '09 I could see the difference when I held the old one up to the new one.

I consider these part of a top end rebuild but if you don't know how old they are, assume they're original and replace them before your piston meets your valves.

Edited by jermag24

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I just replaced the cam chain and tensioner on my 2009 KX450, total cost for the parts was $150, $22 for a flywheel puller and $15 for a PDF service manual off Ebay. IMO the tensioner can be the "ticking time bomb" in modern 4 strokes and, like others have said, the chain does stretch over time. Even on my '09 I could see the difference when I held the old one up to the new one.

I consider these part of a top end rebuild but if you don't know how old they are, assume they're original and replace them before your piston meets your valves.

$150 total? $22+$15=$37.

Buy an oem timing chain off rockymountainmc.com don't hesitate. When i got my '08 bike i adjusted the valves after i got it cause it was hard to start. The valve lash was in spec but the timing was one pin off. I thought whoever the last guy was that timed it was an idiot. Fixed it and rode for a couple weeks. Stalled the bike real hard one day and after that it was really hard to start and didnt sound right when it was running. I pulled the valve cover and checked timing. It was two pins off this time. The chain had a little play but i thought it was fine. Anyway i checked my tensioner and it was fine. Bought a new chain and once the tensioner was installed the chain had almost no play.

So long story short replace it before it jumps time and bends a valve.

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No, $150+$22+15

that's what it cost you just to do the timing chain?

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that's what it cost you just to do the timing chain?

Have you never replaced yours? Let me break it down: $75ish for the OEM cam chain, $75ish for the OEM tensioner, $22 for the flywheel puller (needed to access the cam chain in the bottom end), and $15 for the service manual since I didn't have one. Got it?

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http://devluv.motosport.com/dirtbike/oem-parts/KAWASAKI/2006/KX450F/CAMSHAFT%28S%29~TENSIONER?mmy_source=oem

You can now get the chain and tensioner for about $100. Most likely you will need associated gaskets also on one this old. It would be better to have them on hand if you want to put it back together directly.

The bigger problem... if the chain is that bad how do you think the rest of the major maintenance parts are? The main bearings, big end bearing, water pump bearings, piston, and rings?

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Have you never replaced yours? Let me break it down: $75ish for the OEM cam chain, $75ish for the OEM tensioner, $22 for the flywheel puller (needed to access the cam chain in the bottom end), and $15 for the service manual since I didn't have one. Got it?

An oem timing chain is $41 and tensioner $59 on rockymountain. Yes, as i stated above, I did mine a few months ago. My tensioner was still good so I didnt replace it. I have a drawer in my tool box full of fly wheel pullers from past engine builds so i didnt need to buy that. Timing chain is a fairly simple job so I didnt need the manual.

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