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426 boy

Timing for the first time!!

7 posts in this topic

Hi, i took my cylinder head of for the first time yesterday cause i had a gasket leak. now im putting back together. Im scared of the ''timing'' part of things, like lineing camshafts up and the cam chain. I have the manual and have a good idea of what to do but its a little vague. Is there anything i should watch out for and be careful of when i do this could use please give me some advise thanks cheers.:crazy:

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Make sure you double check the timing marks after you put in the cam chain tensioner. The timing should really only be checked with the tensioner in, but most people don't b/c it's a pain to take it back out to change the timing if you are off a little.. A mistake I've seen a lot is someone checks the timing without the tensioner, throws the tensioner in (which tightens the chain and reveals that the timing is really off a tooth) and doesn't check again. Then they can't figure out why the bike won't run right. I actually saw a shop do this to someone and I had to help figure out what was wrong with the bike.

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Make sure you double check the timing marks after you put in the cam chain tensioner. ... A mistake I've seen a lot is someone checks the timing without the tensioner, throws the tensioner in (which tightens the chain and reveals that the timing is really off a tooth) and doesn't check again.
This is exactly right, but mistiming can be avoided without repeatedly installing/removing the tensioner.

When you've had the head off, there are pretty much 3 things that can go wrong as far as the cam chain is concerned:

> Front guide out of place. Because the front guide stands up so high, it's easily pushed back so that the pegs that locate it at the top of the cylinder are pushed out of place. If this happens, you won't be able to put the exhaust cam in place.

Prevention: raise the head up and check the guide just before you bolt it down.

Correction: unbolt the head and move it.

> Chain has a link hanging free off the bottom of the crank. This is not supposed to happen, as the bracket on the bottom of the rear guide is supposed to prevent it. But if you turn the engine too much or too fast with the tensioner and/or the cams out, you can cause this. You'll know because the chain will just be way too short to put the second cam in.

Prevention: turn the engine only a minimum amount with the chain slacked, and hold tension on the chain when you do.

Correction: remove the flywheel (and stator in '05 and earlier models), and the bolts holding the rear guide, and reposition the chain.

> Mistiming by failing to tension the chain when checking it, as mentioned by KJ.

Prevention: Time the exhaust cam first. When you initially check the timing, rotate the engine backward only a couple of degrees by rotating the cam backward and letting the cam chain pull the crank. Then, turn the crank back forward to TDC, pulling the cam along with it. This will pull the front run of chain tight, just as it will be with the tensioner in place. When setting the intake, again turn the engine backward only a little by turning the exhaust cam, then rotate the intake cam back to pull the slack out of the top run of chain, and rotate the crank gently back to TDC as before. Check both cams. You can also reach through the tensioner hole with a rod or a finger tip and push in on the rear run of chain to simulate the tensioner being in place. When you think you have it, put the tensioner in and double check.

Correction: re-time it.

Also, remember that the timing marks will not line up perfectly in most cases. If it seems a little off with the tension on it, visualize the mark being one tooth farther in either direction and see if that makes it better or worse.

There's also this:

http://www.thumpertalk.com/forum/showthread.php?p=3150405#post3150405

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You can also put your finger in the hole for the tensioner to put tension on the chain. This will take up any slack between the two cams, but it is good to double check the timing again when everything is assembled right before you put the valve cover back on, just to be safe.

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I said that :D

The thing is that the crank is VERY easy to move near TDC, and the process of rolling it forward is partly to avoid having it move off its mark unnoticed. :crazy:

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I just put my top end back on today all went well new 97mm piston AND A NEW cam chain it had kinks in it. for $15.00 change it!

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