87 ATC 250SX Engine Knocking...

[Oakley101]

I was riding my machine, no problems or anything and than i went to park it and it started making this weird noise, im gonna post the link to my youtube video of the engine running. if you have any ideas of what it could be PLEASE help me. i love this machine to death and id rather not screw it up worse than it already is :wondering


video link -------> http://www.youtube.com/watch?v=IfzK6368AqU

[Oakley101]

I was riding my machine, no problems or anything and than i went to park it and it started making this weird noise, im gonna post the link to my youtube video of the engine running. if you have any ideas of what it could be PLEASE help me. i love this machine to death and id rather not screw it up worse than it already is :wondering


video link -------> http://www.youtube.com/watch?v=IfzK6368AqU

[barnett468]

Hello oakley101

xlnt idea with youtube!

Hard for me to tell. I would check valve adjustment, maybe nut backed off. Check timing chain, adjust it look in manual or see you tube vudeo of procedure. chain guide may be worn out also.


hope this info helps

[ColtonGG33]

Yeah I agree with barnett468 it probably has something to do with your timing

[CodyRosa]

Yup, that's what I'd check first. Really only things you'd hear on that top end making a noise. If you don't know how to check valve adjustments watch this video! http://www.youtube.com/watch?v=IHeIXalJ9N8
If you dont know how to adjust the cam chain watch this video here! http://www.youtube.com/watch?v=eAblGUpxBqM
Hope I helped

[barnett468]

Hellooakley101


Duhhh, tensiiner not adjustable, sorry.

Your problem should not be bad cam, piston, head, etc. Check inner head pipe also if it breaks loose it can rattle.

I just looked at manual for you. It is not adjustable, it is automatic so put engine on tdc with t in timing window and mark on cam gear facing up at mark on head. Check valves ,if adjustment is ok then loosen the two bolts on either side of tensioner located on right front side of cylinder by approximately 1/8” and no more.

Below is a description from atc500 for tensioner/cam chain checking procedure.

The spring inside the tensioner should push the tensioner away from the cylinder as you loosen screws if the tensioner is working and the chain is NOT worn beyond service limits.

If the tensioner stays on the head and only the bolts back out then back the bokts out the 1/8” as mentioned and feel if the tensiiner is loose. The gasket may simply be holding it to the head. Wiggle it until it is loose.

At this point if the tensioner is free and does not push back against the bolts but instead remains loose feeling then either the tensioner is bad or chain is too loose and needs replacement.

Inspect tensioner for proper function as explained in manual.

If the items are ok then visually check guides for wear as manual instructs.


Manual from kbonly

http://www.kb0nly.info/ATC/index.php?dir=ATC250SX%2F


Hope this helps

[barnett468]

Hello

Don't be surprised to see a much better and simpler idea than atc500/mine on how to do the chain check.

[dougspcs]

Start simple!! Drop the oil and pull the filter..there will probably be clues trapped in the filter.

Hopefully just a bit of guide shreds..if you don't let it go too long you may get away with a new set of guides and a chain...

Seems consistent for that engine and the location of the noise.

[philgipson]

has the oil been changed lately?if so check the oil filter for proper installation.a backward filter will cause major grief.hole goes toward the cover.

[three_sum]

My dad has an 87 fourtrax 350 and that had a weird noise that would come and go, turned out to be the timing chain. It was worn out and binding so it would make a loud noise. After that was replaced it runs great and no issues. Hopefully its simple!