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Cam Chain Tension and Valve Clearance Questions

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Hey Fellas,

I recently bought a 2003 KLX 400 and have two questions (for now).

I've read alot about the manual cam chain tensioner and know that my auto tensioner is the the "improved oem" version. I recently did a valve adjustment and was shocked at how tight the cam chain was when I re-installed the oem tensioner (I know that is the problem with the updated OEM). I didn't do anything to it when I removed it, I just did the valves and stuck it back in. It was tight enough that I had to use the two mounting bolts to suck it in the final 1/4" or so. Is that normal. I will ultimately be changing to the aftermarket version but just want to make sure I'm ok to run it as is for right now.

One more question.

I also have a bucket and shim valve clearance scenario and would like to get some opinions from the forum.

I checked the valve clearances and determined three of the valves were barely in spec on the tight end and one exhaust valve was out of spec tight. I decided from there that as long as I was shimming out one valve I might as well run all of them out to the loose end of the spec.

I’m going to skip a lot of the not so important details and get right to the chase. After I buttoned up the cams and re-checked my clearances, three of the four valves were right at the top of the range where I wanted them. Unfortunately, one of my exhaust valves gapped a tad wide. The range is 0.20mm to 0.30mm. The gap is reading around 0.32mm.

These are my options as best I can tell:

1. Button it up and run it. 0.02mm loose is ok???

2. Put the old shim back in which will put the valve somewhere around 0.22mm. (not preferred as I would rather get all 4 valves started off in roughly the same gap range)

3. Take the chubby shim to the local machine shop and have them take it down a tad.

All right, what say yee???

Thank for your help!

Chris

NOOB REALIZATION UPDATE:

Alright, I'm slowly figuring this out.

Cam chain tensioner update = I'm an idiot. Turns out I took "automatic" a little too literally. I didn't re-set the tensioner from full extension prior to re-installation. Fortunately my spidey sense told me something wasn't right and I took it right back out without running it.

As far as the shims are concerned, let me start with the fact that i'm a shim NOOB. This is my first bucket and shim bike and I'm learning on the fly. I started with a 3.08mm (OEM size) and needed a 3.05mm to hit my middle of range mark. I stopped by my local dealer to grab a shim and they told me they could only give me a 3.00mm which tossed my gap out wider than I wanted. I have since dug in a little further and realized that aftermarket shims come in 0.05mm increments which means I might have been misled at the parts counter. I should be able to get a 3.05mm shim which will solve my problem as well. I'm still curious as to whether 0.02mm wide will damage anything if I leave it in there.

Edited by Crabenho
Noob Realization Update

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Take that auto cam tensioner out immediately!!! When you remove it, it ratchetes all the way out. Sounds like you did not reset it before the install, and have forced it back in under full extension. Your risking immediate cam chain / cam bearing damage!!!!

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No problem. I recognized I had missed something and took it right back out. How do you re-set it? (I don't have a manual...yet)

Take that auto cam tensioner out immediately!!! When you remove it, it ratchetes all the way out. Sounds like you did not reset it before the install, and have forced it back in under full extension. Your risking immediate cam chain / cam bearing damage!!!!

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Hey Fellas,

I recently bought a 2003 KLX 400 and have two questions (for now).

I've read alot about the manual cam chain tensioner and know that my auto tensioner is the the "improved oem" version. I recently did a valve adjustment and was shocked at how tight the cam chain was when I re-installed the oem tensioner (I know that is the problem with the updated OEM). I didn't do anything to it when I removed it, I just did the valves and stuck it back in. It was tight enough that I had to use the two mounting bolts to suck it in the final 1/4" or so. Is that normal. I will ultimately be changing to the aftermarket version but just want to make sure I'm ok to run it as is for right now.

One more question.

I also have a bucket and shim valve clearance scenario and would like to get some opinions from the forum.

I checked the valve clearances and determined three of the valves were barely in spec on the tight end and one exhaust valve was out of spec tight. I decided from there that as long as I was shimming out one valve I might as well run all of them out to the loose end of the spec.

I’m going to skip a lot of the not so important details and get right to the chase. After I buttoned up the cams and re-checked my clearances, three of the four valves were right at the top of the range where I wanted them. Unfortunately, one of my exhaust valves gapped a tad wide. The range is 0.20mm to 0.30mm. The gap is reading around 0.32mm.

These are my options as best I can tell:

1. Button it up and run it. 0.02mm loose is ok???

2. Put the old shim back in which will put the valve somewhere around 0.22mm. (not preferred as I would rather get all 4 valves started off in roughly the same gap range)

3. Take the chubby shim to the local machine shop and have them take it down a tad.

All right, what say yee???

Thank for your help!

Chris

👍

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I have the manual tensioner and have only messed with the acct enough to remove it. Someone with more knowledge of the acct will chime in, but I believe it involves backing the nut on the back to relieve the tension before installing as to not let it ratchet out until it is fully installed.

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I recently did a valve adjustment and was shocked at how tight the cam chain was when I re-installed the oem tensioner (I know that is the problem with the updated OEM). I didn't do anything to it when I removed it, I just did the valves and stuck it back in. It was tight enough that I had to use the two mounting bolts to suck it in the final 1/4" or so. Is that normal.

That is not correct. 👍 Do not run the bike hard, if at all.

If you have the ratcheting style ACCT: remove the nut and washer holding the spring, and the spring. Then remove the ACCT body. If you look at the mechanism, there's a little tooth that lets the plunger move out, but not back in. You need to push down on the backside of that and push the plunger all the way back in.

Get the engine to TDC.

Re-install the ACCT body. Then install the spring, then install the nut and washer that holds the spring. You will have to push against the spring tension to to get the threads started. You will hear the plunger clicking past the tooth as you put pressure on the spring. Snug down the nut.

For the predecessor to the ratcheting style ACCT, see the shop manual. (PM me.)

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Thanks for the help. I didn't run the the bike. I didn't even rotate the motor. My spidey sense was telling me to bail and start asking questions.

That is not correct. 👍 Do not run the bike hard, if at all.

If you have the ratcheting style ACCT: remove the nut and washer holding the spring, and the spring. Then remove the ACCT body. If you look at the mechanism, there's a little tooth that lets the plunger move out, but not back in. You need to push down on the backside of that and push the plunger all the way back in.

Get the engine to TDC.

Re-install the ACCT body. Then install the spring, then install the nut and washer that holds the spring. You will have to push against the spring tension to to get the threads started. You will hear the plunger clicking past the tooth as you put pressure on the spring. Snug down the nut.

For the predecessor to the ratcheting style ACCT, see the shop manual. (PM me.)

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Also, the valve specs are as follows: .10-.20 for the intake, .20-.30 for the exhaust. .15 for the intake and .25 for the exhaust is the optimal clearance. That is what you should strive for when you are shimming your valves. I would not shim them to give a little more leaniency to prolong another valve adjustment. They are supposed to be at those specs, and they are considered within spec as long as they are within those perameters. When they go out of those perameters, you are supposed to shim them to get as close as possible to .15 intake, and .25 exhaust.

Think of it like your drive chain......You know it's gonna stretch out, however, you still adjust it to give about an inch of play. You wouldn't tighten it all the way up to prolong another chain adjustment in the future because of the damage that would occur. Valve checks and adjustments are just another part of bike maintenance. Go get yourself as set of Hotcams shims, it will make it a lot easier.👍

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Richard, is that you?

Also, the valve specs are as follows: .10-.20 for the intake, .20-.30 for the exhaust. .15 for the intake and .25 for the exhaust is the optimal clearance. That is what you should strive for when you are shimming your valves. I would not shim them to give a little more leaniency to prolong another valve adjustment. They are supposed to be at those specs, and they are considered within spec as long as they are within those perameters. When they go out of those perameters, you are supposed to shim them to get as close as possible to .15 intake, and .25 exhaust.

Think of it like your drive chain......You know it's gonna stretch out, however, you still adjust it to give about an inch of play. You wouldn't tighten it all the way up to prolong another chain adjustment in the future because of the damage that would occur. Valve checks and adjustments are just another part of bike maintenance. Go get yourself as set of Hotcams shims, it will make it a lot easier.👍

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