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Apgar1

Ticking YZ400F

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I just got a 98 YZ400 and i noticed a loud tick when you open the throttle at a lower rpm. What causes this?

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Valves don't know the throttle is open. It's more likely an exhaust leak, a head gasket leak, or a pinging condition caused by low octane fuel.

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I have a full powerbomb on it and that makes sense. It does have a small leak where the two pipes meet. I was woried about the top end. How can i tell when it need the timing chain changed? It starts on the first or second kick every time.

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How can i tell when it need the timing chain changed?

If you don't know when the last one was installed, it needs one.

You can visually inspect the chain in several ways. Wear can be seen on the driven faces of the plates. If the tensioner is slacked off (only do this at near TDC on compression, and don't turn the engine over while the tensioner is slack), you can check for stiff, binding links. If you remove the chain, the amount that the chain can be curved sideways is another indication.

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