engine noise
  • stokes 436
    Posts: 11
    Joined: Sun Jan 04, 2015 7:41 pm

    engine noise

    by stokes 436 » Sun Jan 04, 2015 8:46 pm

    2008 crf250x
    Looking for some help, been having a whining sound from the top end? Its a whining sound like gears that don't mesh right. First started only when the motor was hot. Eventually started to make the noise as soon as it heats up. There is no power loss or anything obviously wrong.Checked the valves and they are in spec. Was wondering about a worn cam bearing or cam chain guides? I have put 50 or 60 hours on the bike since I bought it a year ago. The bike was in new condition when I bought it. Any help would be appreciated.
  • hall_philip
    Posts: 141
    Joined: Mon Mar 04, 2013 5:17 pm

    by hall_philip » Mon Jan 05, 2015 6:14 pm

    I would pull the cam and check for a spun bearing, if it spun in the caps you might need to have a machine shop repair the head or you might have got lucky and it just spun on the camshaft itself then you just buy a new cam.
  • stokes 436
    Posts: 11
    Joined: Sun Jan 04, 2015 7:41 pm

    by stokes 436 » Mon Jan 05, 2015 8:05 pm

    thanks for the advice. If the bearing spun in the bearing cap it would be obvious, but if it spins on the cam how can I tell? would the valve specs. be out? all valves measured perfect. Intakes were .002mm tight and exhaust right on. No difference from side to side.
  • hall_philip
    Posts: 141
    Joined: Mon Mar 04, 2013 5:17 pm

    by hall_philip » Tue Jan 06, 2015 2:50 pm

    the bearings are not sealed, they are an open bath bearing. so if you remove the camshaft and the bearing either doesn't spin at all or spins roughly, I have seen the inner bearing race lock up and the cam spin on the ID of the bearing. usually something like this happens from oil contamination or neglect, being as that's where this bearing gets it lubrication from, also heat.
  • stokes 436
    Posts: 11
    Joined: Sun Jan 04, 2015 7:41 pm

    by stokes 436 » Sun Jan 18, 2015 7:07 am

    Thanks again for the info. I pulled the cam and it had some scratches on the bearing caps and on the bearing face of the head.The bearings appear to be ok, they don't have any roughness when turning and they are free moving on the cam. The only thing is the scratches on the outside of the bearings and the bearing faces. Both bearings appear to of spun. Could this happen if someone didn't torque the cam properly?
  • hall_philip
    Posts: 141
    Joined: Mon Mar 04, 2013 5:17 pm

    by hall_philip » Sun Jan 18, 2015 9:19 am

    most certainly could have. does the O.D of the bearing have any alum. from the caps fused into it?
  • stokes 436
    Posts: 11
    Joined: Sun Jan 04, 2015 7:41 pm

    by stokes 436 » Sun Jan 18, 2015 9:40 am

    There is only scratches, not deep enough to feel. no metal transfer at all. The bearings appear to be free on the cam. they spin very well, no binding or roughness at all. Bearing cap bolts didn't appear to be torqued the same.
  • hall_philip
    Posts: 141
    Joined: Mon Mar 04, 2013 5:17 pm

    by hall_philip » Sun Jan 18, 2015 12:05 pm

    if there was no damage to the caps I would say to put it back together and make sure the bolts get torqued to the right value. the best way to do them is in baby steps not all at once.
  • stokes 436
    Posts: 11
    Joined: Sun Jan 04, 2015 7:41 pm

    by stokes 436 » Sun Jan 18, 2015 6:49 pm

    That's great news. Hoping to go to Georgia in March again. A new cam would be a cramp in the plans for sure. The person I bought the bike from seemed like they new what they were doing. They had other bikes, mine was the first full size bike for the son. The dad rode a Hausenburg 350 and there was a blown up yz250 2 stroke. They sold the crf to fix the yz. the bike came with 3 left side gaskets some o rings and oil filter springs and spark plugs. The bike had original tires, sprockets and chain. The side covers didn't even have a scratch on them. I know that the kid may of done some stuff to it that is why I questioned the torque of the caps.
  • stokes 436
    Posts: 11
    Joined: Sun Jan 04, 2015 7:41 pm

    by stokes 436 » Fri Jan 30, 2015 8:51 pm

    Thanks for all the feedback!! I run 91 octane fuel and found it ok. Tried some racing fuel mixed 70% gas and 30% race and what a difference started better hot, no hot start at all and way more throttle response. I would recommend it!!
    I don't think the bearings are bad with all the help I've had on this. I was wondering about the rocker arm. Does the bearing ever go? How do I test that one? Still looking for that sound.

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