PLS - Help: My 2004 YFM350 has developed a grinding sound

[oktrg500]

Hi friends,

I am really hoping for some help here, because my local workshop only says the cause could be everything.

Last week I noticed a sort of grinding sound from the engine. It lasted about one minute after warming up the engine. Then it was

not noticeably.

I know I should have checked the engine oil for fragments of metal, but it is still rather cold in Norway and doing maintenance out

in the cold is not what I am looking forward to.

This week the sound has developed and has become much more noticeable. As of now, it still almost disappears when the engine gets

hot.

As far as I know, the ATV has had 2 owners before me and it has been very well cared for. Judging from the condition when I bought it, it is a low mile runner.

I wonder what could this be?

I've been a twostroke only guy for more than 40 years, so I'm in unknown terrain here.

Thank you very much for helping me getting to the bottom of this issue.

Regards
Ole Knut
Norway

 

[beastlywarrior228]

Wow that's clean. I would start by going through and checking things like the timing chain and guides.

 

[PineyPower]

Mine made a very similar noise when the flywheel bolt got loose. The little cover on the left side, pull it off and make sure the 17mm bolt in the crank is good and tight