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nolzey

help!!!!!!!!!

18 posts in this topic

im am rebuilding my yz400f 99 and im up 2 the timming chain ( this is my first bike motor) how presice are the timing marks. with the bottom lined up to the i mark i can see both dots on the exhaust cam and 1 on the intake but it is only out by a flyshit (1 to 2mm) and it would be perfect. could the timing chain be a little streached? i know i should have put in a new one but i didnt. when i set the cams up perfect the i mark is out about 2 to 3mm off. or is that 1 tooth out on the bottom?

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Do a search on that if you already haven't. There are alot of posts on that topic.

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The question is, if you moved the cam one tooth in either direction, would it be closer, or farther from lining up?

The timing marks will rarely line up perfectly because the length of the chain exaggerates the smallest amount of wear (stretch). If moving it won't improve it, it's lined up right.

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thanks i realised that if i moved it anyway it would be out alot more. i should have put a new chain in !!!!!!!!!!! ill lern the hard way.

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If you are still in the cam chain timing change it is not too late to change it. You would only have the pull the left side (mag) cover, and on chain guide (if I recall correctly). Chain is only around $30.00.

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With no intent of discouraging anyone, the flywheel and stator plate must also be removed. Easy job, none the less.

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If you are still in the cam chain timing change it is not too late to change it. You would only have the pull the left side (mag) cover, and on chain guide (if I recall correctly). Chain is only around $30.00.

With the right tool...... idealy a impact screwdriver and a torx bit that fits.

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With no intent of discouraging anyone, the flywheel and stator plate must also be removed. Easy job, none the less.

True that! I guess I was in a hurry while typing. Thanks for keeping us on track Gray.

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With the right tool...... idealy a impact screwdriver and a torx bit that fits.

Flywheel puller too. Do it now if it's already opened up.

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well i havent changed the timing chain yet but i think i need to:foul: there is a ticking noise in the top end now, well it was always there but getting worse. when the head was machined they did the cylinder as well so i lost a couple thou and fitted the hi comp piston and i think with the streach in the timing chain is causing the valve to just hit the top of the piston:cry: . i have 1 value that keeps needing adjusting as well, could this be the 1 hittin the piston? should i start wif the chain?

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Definitely replace the chain. After all of the work and $$ you put in to the head, not replacing a $30 part can potentially cost you hundreds more.

Which valve is always needing to be reshimmed? And is it the same valve everytime you check them?

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yer ill do the chain shortly. yer its the same valve all the time the kick side intake valve. the machinest said the seats were really bad and i dont know how deap he took the seat down to seal it. maybe its gone sort too. ive got around 145 shims in all the buckets except the problem valve which has a 125 in it.

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If there is just that one valve that needs to be reshimmed every few hours, then you definitely have a problem with it.

Did the '99s use stainless steel valves? If so, I'd consider replacing that valve, or at least having the head looked at by another shop.

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yer stainless in the 99, i might pull it down again and get new valves and seats and chain. any idea if i can use titanium valves out of a 426?

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Not sure, but why would you want to?

The SS valves tend to last longer from what I've read here.

Once the ti valves wear through the very thin layer of hardness, they wear considerably faster than the SS valves.

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Reassembly tip: Get some soft clay and put some small pieces on the piston just under the valves. Fully assemble the head (including chain) and turn it over carefully a few times. Remove the head and check out the clay pieces carefully. That will tell you if the valves and piston are making any contact. With all OEM parts there's no real reason to believe that parts would be making contact, assuming it's assembled correctly, but if you start buying parts ala-carte then this can help save you some serious cash. Good luck!

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