Anyone know what this noise is?

[Munch1]

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!

[TDW]

I dont think that noise is from the decompressor, I would say timing chain and/or tensioner. When getting an older bike like that especially with a noise in it, it would make sense to do alot of checking before dis assembling it and going through the engine. It could have ALOT of hours on it, it does look like the cylinder was replaced at some point.

[Munch1]

4 minutes ago, TDW said:

I dont think that noise is from the decompressor, I would say timing chain and/or tensioner. When getting an older bike like that especially with a noise in it, it would make sense to do alot of checking before dis assembling it and going through the engine. It could have ALOT of hours on it, it does look like the cylinder was replaced at some point.

Would the timing chain not be noisy all the time? Under load ect? I am talking about the noise as the bike drops down to really low rpm and is about to die. 

 

I originally bought it to split for parts because it was so cheap but if I can get the noise gone I may just sell it on for some fast profit.. 

[TDW]

1 hour ago, Munch1 said:

Would the timing chain not be noisy all the time? Under load ect? I am talking about the noise as the bike drops down to really low rpm and is about to die. 

 

I originally bought it to split for parts because it was so cheap but if I can get the noise gone I may just sell it on for some fast profit.. 

The noise from a loose timing chain or bad tensioner can be noticeable at idle because of the "roughness", it naturally smooths out with acceleration and higher rpm especially with a load because everything gets tightened up, until you chop the throttle or throttle down which at that point the load reverses through the drive train including into the timing chain and then is when the chain would most likely "jump" a tooth or two and cause engine damage, and often times alot of it!

[Munch1]

20 hours ago, TDW said:

The noise from a loose timing chain or bad tensioner can be noticeable at idle because of the "roughness", it naturally smooths out with acceleration and higher rpm especially with a load because everything gets tightened up, until you chop the throttle or throttle down which at that point the load reverses through the drive train including into the timing chain and then is when the chain would most likely "jump" a tooth or two and cause engine damage, and often times alot of it!

 

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!

[TDW]

2 hours ago, Munch1 said:

 

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!

All I can say is good luck!