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Author Topic: CRF450x Engine Knocking sound  (Read 959 times)

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Offline blauth

CRF450x Engine Knocking sound
« on: February 03, 2014, 05:42:01 pm »
Hello Lads,

I've just bought a CRF450x 2010 model. Original rear tyre (albeit smooth) still but somewhat poorly maintained. The bike hasn't been ridden hard.

I didn't notice a knocking sound when I test rode the bike but I can't honestly say I tried particularly hard to listen for one.

So as soon as I got it home, I lubed chains, oiled airfilter that was bone dry and did oil change on gearbox (750ml) and clutch (750ml - slightly more than recommended as per various recommendations).

Then I started her up and there is a very distinct knocking in the engine. It appears to be when the engine isn't under load. I took it to a mate who races MX and run an MX team and we pulled the tapped cover off. It looks new up there. Decompression mechanism is fine, timing chain is fine, valve clearances are correct.

There are no filings in the oil.

So I decided to ride it either way (all or nothing attitude) and she got hammered at the MX track for about four 18 laps. It pulled well with no hickups but the knock is still there and still worrying me.

Any suggestions as to where to start looking?
Please don't everyone jump to the preverbial 'Big End is gone' conclusion. The knock quietens down when under load or revving her up.

Thanks
Barry

Offline sidetrack

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Re: CRF450x Engine Knocking sound
« Reply #1 on: February 03, 2014, 06:00:50 pm »
Tried increasing the idle speed ? Maybe too low and the decomp is kicking in.
Little by little, one travels far
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Offline blauth

Re: CRF450x Engine Knocking sound
« Reply #2 on: February 03, 2014, 08:53:09 pm »
It still knocks a bit idling very high, probably in the region of 3k rpm.

I'll drain the oil again and check for metal filings now after I've ridden it a bit.

Offline wolf skaap

Re: CRF450x Engine Knocking sound
« Reply #3 on: February 03, 2014, 09:53:44 pm »
Take it to Bikequip.
Internet is not the place to diagnose a big end.
 ;)
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Offline sidetrack

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Re: CRF450x Engine Knocking sound
« Reply #4 on: February 03, 2014, 11:08:43 pm »
Also I have never found that screwdriver to the ear and motor to search for a noise to work. Any mechanical sound gets amplified on a bike and you end up suspecting all kinds of faults.
Little by little, one travels far
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Offline steveindar

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Re: CRF450x Engine Knocking sound
« Reply #5 on: June 16, 2014, 10:47:00 am »
Please don't everyone jump to the preverbial 'Big End is gone' conclusion.

Definitely Big End..... :pot:

You fix it yet?
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Offline Mapog

Re: CRF450x Engine Knocking sound
« Reply #6 on: June 16, 2014, 06:42:48 pm »
KInd of an old tread, but where does this bike originate from. I looked at one at that time of year(In NC) and also heard a noise in engine?