Forum Main Tech Help/Race Shop CRF 250 2004 decomp lever noise?

CRF 250 2004 decomp lever noise?

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munch

Vital MX member munch 43059 munch /images/default/avatar/c50.png https://www.vitalmx.com/community/munch,43059/all 05/04/14 12 23

Posts: 35

Joined: 5/4/2014

Location: GBR

8/4/2017 4:03 PM

Hi guys just picked up this 2004 250r for dirt cheap, it has an odd noise which I think is the decomp working at very low RPM for some reason but I want other opinions.

Video:



The idle isn't great as you can tell, in the beginning I am saving it by giving it a little gas but at around 0:20 the idle starts to come down and around 0:22 you can hear it going to die and making the noise which I think is the decomp. It only ever happens at extremely low RPM as it's about to die and I think if I sorted the idle so it didn't drop down it would go away.

Can someone confirm? I don't think it's the chain as I think for such an old motor it sounds pretty healthy!
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Paw Paw

Vital MX member Paw Paw 31735 Paw Paw /images/default/avatar/c50.png https://www.vitalmx.com/community/Paw-Paw,31735/all 12/24/11 1 680

Posts: 681

Joined: 12/24/2011

Location: Benton, LA USA

8/5/2017 1:45 PM

Cam chain may be worn out and the valves sound to be loose.

Paw Paw

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munch

Vital MX member munch 43059 munch /images/default/avatar/c50.png https://www.vitalmx.com/community/munch,43059/all 05/04/14 12 23

Posts: 35

Joined: 5/4/2014

Location: GBR

8/5/2017 3:26 PM

Paw Paw wrote:

Cam chain may be worn out and the valves sound to be loose.

Paw Paw

...more

Surely it being driven for approx 10 hours with the same exact noise by now it would have skipped a tooth? I rode it for approx 10min myself pretty hard and have done a fair few throttle chops when listening to noises ect.. If the chain was so bad to make such a loud noise at low RPM wouldn't it also be noisy at high rpm and just general idling since the chain would be super super loose? Also would it still start first kick? It starts great hot and cold!

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Paw Paw

Vital MX member Paw Paw 31735 Paw Paw /images/default/avatar/c50.png https://www.vitalmx.com/community/Paw-Paw,31735/all 12/24/11 1 680

Posts: 681

Joined: 12/24/2011

Location: Benton, LA USA

8/5/2017 5:38 PM
Edited Date/Time: 8/5/2017 5:39 PM

OK, then why did you ask if you seem to know the answer??????
By the way...If the decompression arm was making that much noise you would not be able to kick it over.
The point is that you will need to do further investigating to find the source of the problem. I gave you the most common, but remember I am not there with the bike.
I do suggest that you again check your valve clearances and if you have not changed the cam chain you do so before you blow the engine up.
There can be other reasons for the noise too.

Paw Paw

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