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ozonefirefighter

timing chain change

7 posts in this topic

ok i just changed my timing chain on my 99 400. but when i took it out and compared it to my new one the chain has not stretched. the only reason i chainged it was cause it jumped a tooth so i figured it had stretched. so did i just do this for no reason? should i keep the old one as a replacement since it isnt stretched? y did my chain jump if it wasnt stretched?

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onother question if the intake cam is bolted down without the chain on it should it turn freely by hand? mine dosnt

Sounds as if the cam cap was over torqued... a very easy thing to do... I have seen bikes with this condition run for many years but since you had a chain jump I would check into it a little closer...

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The cam should spin freely if the cam cap is torqued down to spec. If it doesn't then the cap was probably over torqued which would cause the cam to bind/seize (maybe just momentarily) in the journals and explain why the chain jumped a tooth. Or, you have an oiling issue with the head which caused the cam to seize. Do the journals looked scored or grooved?

Also, the recommended torque is 86 in-lb (NOT 86 ft-lb), with the general consesus being to use even less or about 75 in-lb.

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I would assume the cam would not spin "freely" but rather have some resistence due to the valves. Now binding is another issue.

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Cam should definitely spin freely between 9 and 3 o'clock on the lobes, but once the lobes touch the buckets you will get resistance.

As stated above 75in/lbs is good.

Keep your chain as a backup if you are 100% sure it's not stretched.

Have you checked that your tensioner is fully functional?

If you take the cam off, are there score marks on the cap where the cam rides/spins on it (journals)?

Is your locating half ring in place?

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