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98Thumpin400f

engine noise?

4 posts in this topic

I just bought a 98 YZ400F and I am not real familiar with these big four strokes are these engines just noisy? How often should you adjust the valves? How hard is it to adjust the valves? How much noise will valves in need of adjustment make? Thank you for any input.

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Welcome to TT! Many people will tell you to search before asking, but I think new threads are good.

Buy a shop manual before you do anything else, its worth whatever they cost. The valves should be checked a couple times a year. The 400's didn't have Ti valves so they really don't wear that fast. The engine noise you maybe hearing is the timing chain, it should be replaced once a year. A worn timing chain will eat your crank gear if you don't change it.

Checking the valves only takes about a half hour at the most. The manual shows step by step how to do it. The timing chain will take a couple hours if you haven't done one before, and it requires a mag puller.

And yes, these 4 strokes are noisy. You'll get used to it after awhile.

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Thanks for the input I plan on getting a manual as soon as possible. So you don't have to split the case to change the timing chain? Thanks again

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Thanks for the input I plan on getting a manual as soon as possible. So you don't have to split the case to change the timing chain? Thanks again

No case splitting, you just have to remove the valve cover, cams, mag cover, flywheel, and stator plate. Its not hard at all. You maybe able to download a manual too, just search for it and you'll probably find it.

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