[Munch]

Hi guys, I purchased a 2008 crf 250 a few days ago and the engine seems very noisy, I have done some searching about and people say the engine is noisy anyway but I'm not sure if the noise mine is making is normal, it's my first 4 stroke.

Video of noise:
https://www.youtube.com/watch?v=PpWDRNEs79A

[JimDirt]

Welcome to the site !!

It could be the timing chain slapping , but it kind of sounds "normal" to me , the engine will always be noisier on the exhaust side because the sound resonates and its like putting nuts and bolts in a can and shaking it , when listening on the exhaust side , its always louder than the ignition side

You can perform a small test to see if its the chain by looking at the chain tensioner/adjuster at the back of the head on the ignition side , remove the 8mm bolt and take a very small(short also) flat blade screwdriver , and start the bike , while its idling , slightly (don't force it just barely move it) turn it in/out in either direction 1/4 turn or less, if it quiets up , or gets louder you can eliminate or confirm its the chain and/or tensioner , (if it gets quieter when turning in but gets noisy again when you remove the screwdriver and let it return to its original tension , then either the tensioner is weak or the chain has stretched , of course replacing the tensioner is much simpler than the chain , but both can be done easily with minimal effort (the only specialty tool will be a Flywheel Puller *made specifically for the CRF250*)

The timing chain will loosen similar to a drive chain , it stretches over time and depending on the abuse it receives it can stretch faster or hardly at all , generally people replace the chain when doing a piston replacement as its the opportune time to do this , and they are relatively inexpensive ($40-$60)



The tensioner is "supposed to" return to position and hold tension on its own without user input , so if its not holding the chain at the proper tension , it means the spring has become weak , which means the tensioner needs to be replaced , i prefer OEM units as opposed to manually adjusted ones , but its all personal preference, do you know if the engine has been rebuilt ?? and if the chain was replaced at that time ?? , do you know how many hours are on the engine/bike total and/or since a rebuild ??