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4 stroke knocking sounds when accelerating

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This is not related specifically to the 450x, but most bikes I think. When you grab a handful of throttle and you are in much too high of a gear, the bike makes a horrible knocking/clanking noise. Obviously shifting down resolves this, but do you know what makes that knocking noise? Is it something in the tranmission?

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Probably chain slap.. Pretty common on alot of the new four strokes.. especially if your in too low of a gear for the situation.. Proper chain adjustment most of the time will make it go away! If that's not your problem. Than you got issues! :banghead:

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This is not related specifically to the 450x, but most bikes I think. When you grab a handful of throttle and you are in much too high of a gear, the bike makes a horrible knocking/clanking noise. Obviously shifting down resolves this, but do you know what makes that knocking noise? Is it something in the tranmission?

On most non high performance 4 strokes, it sounds like you're talking about spark knocking from premature combustion. I'm not exactly sure why they will do it, but it is probably caused by excessive heat in conjuction with excess fuel admitted in the combustion chamber. I've only heard it on a couple of my low performance dual sport bikes. This will also happen when you use too low of fuel octane.

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I have the same issue with my CRF250X and it does go away with chain adjustment but the cahin appears to be too tight, tighter than the 1.5" specification. I run BP 93 octane fuel.

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Chain slap. Run your chain around 1" of slack at the tightest point. (found by spinning the wheel and checking tension in different spots)

For extreme mud riding set it to factory specs.

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I didn't consider chain slap because it's too obvious. I assumed he would know chain slap when he hears it. :banghead:

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Don't forget about the timing chain slapping when loose. You won't get away with the cam chain slapping for long though! :banghead::banghead:

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I didn't consider chain slap because it's too obvious. I assumed he would know chain slap when he hears it. :banghead:

A friend of mine sold his 450 to a dude that mistakenly self diagnosed chain slap as something knocking in the engine. He took it to the local Honda dealer after his shade tree mechanic buddy told him something was wrong with the engine. they instructed the dealer to check everything in the topend, compression, valves, etc.

He ended up paying $150 to get his chain tightened after everything else checked out spot on.

:banghead:

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i had this problem at first with my bike. it was from not using high enough octane fuel like biznet1 says. its spark knock..

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put a new chain slider on the swingarm and the sound will disappear.

I was one of the 1st to have a yz400 and after about 125 hrs or so this sound started. I rebuilt the topend and still had the problem. Changed the chain buffer and sound disappeared.

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Chain slap. Run your chain around 1" of slack at the tightest point. (found by spinning the wheel and checking tension in different spots)

For extreme mud riding set it to factory specs.

Adjusted to 1" and the noise is gone! (seems a little tight to me though)

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Sometimes I hear banging from the engine when I am a gear to high in the sand. It most definately is not chain slap. Like detonating to early. Someone mentioned it above. I was wondering if anyone can clearify. :banghead:

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Its detonation and if you keep doing it, you'll end up blasting the top ring land off the piston and hammering the wrist pin bearing out of it.

Buy some better gas or start using your head and the transmission a lot more....

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I've heard this noise on my cr250 before, when bogging up a hill. I think it's chain slap too. The engine is struggling to make power and when it hits compression stroke it snaps the chain then goes slack again because there is to much strain on the engine. :banghead:

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