01 yzf 426 knocking sound identyfication


I'm new in thumpertalk. I'm glad I can ask a question and get answers from very experienced yz owners.

I bought 01 yzf 426 in good condition. The previous owner of the bike bought it in Holand after service and didn't make any maintenance. He has riden the bike only 10 times on the fields. It was his first motorcycle so that's why he sold it. (to much power).

First I checked valve clerance, two valves are two tight. On intake is 0,9 and one exhaust is 0,13. The chain has no slak it is very stiff. I've tried to move it up and down but it was really stiff. So I think it is preaty new and in good condition.

I've took a ride. 50 km on track and in woods. But not forcing the bike. When I was arriving home I heard strange noise while slowing down and engine braking. And when driving on low revs. I thought that it was a chain. But the sound is "faster" and comes from top of engine.

When I'm reving the bike the sound disappears. On the neutral it is imposible to hear this sound on eny revs. Also when I put my bike in front of the wall and slowly release the cluch on 1 gear It is imposible to hear anything. Normaly the engine work is really silent.

Could you tell me what to do?

Change the chain even if there is no play on it?

I would check the oil and make sure it has oil in it first.

It could be many things but I would not think the chain would be one of them if the noise gets quiet when you rev the engine.

Thanks mate.

First I'll change the oil and filters. The oil level is high and the oil looks like new. But I know that the oil keeps engine alive ;-) . Do you think that old oil could cause this kind of engine noise. (like drive chain but in the engine)

Sounds like chain slap to me. Check drive chain tension and see if that helps.

The YZF engine is well known as a noisy one. Some of what you hear is "cam flip". The cam has to be forced to turn until the lobe goes over center, but after that, at low speeds, the spring pressure drives the cam forward faster than the timing chain does. This results in a slight rattling noise which vanishes as soon as a high enough engine speed is reached.

There is also a torsional rattle in the transmission resulting from the fact that the engine speeds up with each power stroke, then abruptly slows down again with the next compression stroke. This will go away when you pull the clutch in to stop the trans from following the engine, or again, when a high enough speed is reached.

And, of course, there is the normal amount of mechanical noise coming just from the valve clearance.

Most of it is probably normal. Compare with another one to see if yours is abnormally loud.

I chased a similar noise on my 426. Ended up, after changing cam chain, and a lot of other stuff, the primary drive nut on the RH side of the crank had loosed up. The folding lock washer had not been folded over from the factory. The nut is suppose to be torqued to about 54 ft lbs. I spun it off with my fingers. It hold two gears off the end of the crank, the oil pump and the clutch basket drive. The outer gear was worn funny and the keyway was almost sheared. I just overhauled the engine and there are no more funny noises. After seeing that it was a factory defect I know that mine is probably not the only one. Good luck!!

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