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1999 YZ400F........God made this bike for me!!lol

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hey guys!

I have not been in here for a while. I am enjoying every moment on my 1999 YZ400F :D . I bought it with my own money and bought all the gear and modifications myself with alot of hard work :):p . So with saying that I love this bike and want to make sure it runs well ;) . Ive had it for a year and have had no problems.The thing is like a rock :D ! I am thinking about taking it apart and checking some things just because its 6 years old and have been reading things on valves and adjusting them :) . What would you say I should look at?

Also I'm a fairly big 16 year old at 6 foot8 1/2, 215 pounds :o . What other mods could i do to make the bike fit me better :D .

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It would be a good idea to check your valve clearances. This is about a 10 minute job. If you have to adjust them, plan on it taking a few hours your first time. I would also have a look at your clutch. Six years of abuse from that 400cc motor may have taken its toll. I would also check the ends of your throttle cables. They have been known to fray. You definately don't want those braking, especially when you're WFO. It would also be a good idea to check your linkage, wheel and head stem bearings. If they've never been lubed or replaced, chances are you'll need to replace them. You may also want to change your fork and shock oil. It does break down over time. Also, it probably wouldn't hurt to change your brake fluid. It gets dirty too.

This would be a good start. Have fun.

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I have checked everything that you listed apart from the fork oil. I will replace that. But the bike is in amazing condition! I think in its life time before I bought it, it was ridden maybe 6 times. There are no chips in the paint on the frame, it had the original tires, and had a FMF PowerCore 4 series 1 on it. I got it for $2,700.

Since then I have checked everything on it and changed the oil and filter every other ride along with cleaning the air filter every ride. I lubed everything and checked everything.I go threw tires like every other ride :) and replace them with 739's :D "they loose tread too fast" .I put a FMF Powerbomb header,FMF Powercore 4 seers 2 on it along with full FX graphics and renthal bars and UNI Filter :) . The bike only has a couple nicks on it but thats on the front frender and i fix that with fender nu :p . It looks brand new.

But i am concerned about the valves.Other than the valves in my mind it runs fine.Can keep up with 450's all day long :D .

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You might want to consider replacing the timing chain. There wa a rash of timing chain failers on the 99's a year of so back. I am guessing that they started to hit there service limit and were streatching and jumping timing. My bike included. Chain is only like $35. Cheep insurance against valvetrail/piston failers.

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You might want to consider replacing the timing chain. There wa a rash of timing chain failers on the 99's a year of so back. I am guessing that they started to hit there service limit and were streatching and jumping timing. My bike included. Chain is only like $35. Cheep insurance against valvetrail/piston failers.

I can vouch for that.

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yikes, ive got the 99, no probs yet...its in pieces in my basement now so im going to replace that timing chain for sure then!!!

thanx for the heads up.........

my 99 runs mint.....i can vouch for the fraying throttle cables though im replacing my second set in 2 years........why does this happen?? is their anyway you can prevent this???

oh and how hard of a job is this? how many hours if i took it to a shop? engine removed from bike........

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yikes, ive got the 99, no probs yet...its in pieces in my basement now so im going to replace that timing chain for sure then!!!

thanx for the heads up.........

my 99 runs mint.....i can vouch for the fraying throttle cables though im replacing my second set in 2 years........why does this happen?? is their anyway you can prevent this???

oh and how hard of a job is this? how many hours if i took it to a shop? engine removed from bike........

To replace the timing chain is pretty easy. The correct way is to remove the head/ cylinder/ and cam chain guides. Then remove the flywheel and the chain comes out easily. If you dont remove the cylinder/ chain guides there isn't really enough room between the crank sprocket and the front chain guide to get the chain out. I did it but it wasn't pretty or recomended (lots of prying involved)

The throttle cables....I dont know why they fray. Zip Tie racing makes a replacment throttle wheel (round wheel gizmo on the carb). Maybe to fix this problem. I installed Motion pro T2 throtle cables on mine and havent had any problems since. I had broken 2 cables before that. Always the return cable. Never the pull one. Go figure.

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You dont need to take the engine out of the frame.

It is possible but a tight fit to even change out the timing chain without taking the head off. First you need to take both the cams out, the timing chain tensioner, and the flywheel and stator. Behind the stator you will find the timing chain which is held in line by 2 plastic guides, which you unbolt and move farthest away as possible. Take the timing chain out with a mixture of pulling and cranking the motor over via the nut on the end of the crank and it should come right out. You can get the new chain on with a mixture of pushing and turning the crank. It isnt too hard, im sure you can do it.

Yzman and myself have both done them this way.

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