Intake valves hit piston at tdc
  • Crf dirthog
    Posts: 4
    Joined: Thu Aug 22, 2019 11:04 am

    Intake valves hit piston at tdc

    by Crf dirthog » Thu Aug 22, 2019 1:20 pm

    I Rebuilt this bike recently and after setting the timing I tried to spin the camshaft. The valves hit the piston just after the piston passes tdc like as if the valve is going down faster than the piston therefore causing the camshaft to jam. It seems like the cam timing is advanced, but all the marks seem to line up. It has a stock head, stock crankshaft, Wiseco piston, and Wiseco valves. Can anyone help me out with what might be wrong? I can see nothing wrong with the timing but could be missing something.
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    JimDirt
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    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Intake valves hit piston at tdc

    by JimDirt » Thu Aug 22, 2019 3:11 pm

    Welcome to the site !! \:D/

    Are you sure you are not 180 out on timing ??? , even being 1 or 2 teeth off should not allow it to hit/jam up , , did you push on the timing chain at the tensioner when checking the timing ?? , What year bike is it ???
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Crf dirthog
    Posts: 4
    Joined: Thu Aug 22, 2019 11:04 am

    Re: Intake valves hit piston at tdc

    by Crf dirthog » Thu Aug 22, 2019 4:12 pm

    It is an 07 and unless I’m mistaken I don’t think you can’t have it 180 off because the cam chain sprocket bolts don’t align unless turned the proper direction.
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    JimDirt
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    Re: Intake valves hit piston at tdc

    by JimDirt » Thu Aug 22, 2019 5:22 pm

    OK , so when you have the mark aligned in the large round plug on the clutch side , The lobes are facing the rear of the engine at around 2-O'clock looking from the left and the mark on the cam is aligned with the mark on the tower , the valves (both Intake and Exhaust) are loose , correct ?? , this would indicate TDC COMPRESSION , not TDC Exhaust stroke , you should have 0.006 (+/-0.001) Intake and 0.010 (+/-0.001) Exhaust ..... Unless you did not have the tower seated all the way and tightened down and/or the timing chain tensioner was not in and the chain moved

    When you rotate the engine , it stops in the same place every time correct ??? , what does it do if you (remove the spark plug) put the bike in gear on a stand and try to turn the engine backwards using the rear wheel , does it lock up that way as well ??
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Aussiecrf230
    Posts: 1962
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: Intake valves hit piston at tdc

    by Aussiecrf230 » Thu Aug 22, 2019 10:03 pm

    Don't know the motor from personal use, but can the piston be back the front meaning the inlets can hit the exhaust cutouts in the piston.
    Have seen the issue in other motors.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
  • Crf dirthog
    Posts: 4
    Joined: Thu Aug 22, 2019 11:04 am

    Re: Intake valves hit piston at tdc

    by Crf dirthog » Fri Aug 23, 2019 1:09 pm

    Yes the piston is in the correct way. The motor does spin over but it has a definite tight spot when the valves hit the piston so I know something is not right. I have checked the valve clearances and they are all within specs.
  • Aussiecrf230
    Posts: 1962
    Joined: Fri Jan 06, 2006 11:11 pm

    Re: Intake valves hit piston at tdc

    by Aussiecrf230 » Fri Aug 23, 2019 10:55 pm

    Is this the original cam or a new one as part of the rebuild.
    Can you see a valve hit a piston through the plug hole.
    Is the auto decompression adjusted properly?

    Just throwing some ideas out there, you may have checked them already.
    Ray
    Australia

    CRF230F 2004
    C30F Power Up needle
    Mains 132
    Idle 45
    2 turns out
    Baffle out, Screens In

    It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas
  • Crf dirthog
    Posts: 4
    Joined: Thu Aug 22, 2019 11:04 am

    Re: Intake valves hit piston at tdc

    by Crf dirthog » Sat Aug 24, 2019 7:09 am

    The camshaft is a hotcams stage 1 cam but it is supposed to work with my bike. I cannot see the valves hit the piston but I put a thin film of grease on the valves so I can see were it hits the piston when I pull the head off.
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    JimDirt
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    Re: Intake valves hit piston at tdc

    by JimDirt » Sat Aug 24, 2019 10:26 am

    I am still thinking this is a Timing issue ....... You did not mention when I asked about the orientation of the cam lobes (facing front or rear , up or down) , if the mark on the Balancer shaft and the cam are aligned with their marks , it would be almost impossible for the valves to hit ....... There is a exception ......... IF .... You installed or mis timed the Balancer shaft and the mark is aligning to a out of time balancer shaft/gear ......... Then you would be out of time no matter what you confirmed with the cam and gear marks ......... :-k
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Mike Needs help
    Posts: 1
    Joined: Mon Aug 24, 2020 6:18 pm

    Re: Intake valves hit piston at tdc

    by Mike Needs help » Mon Aug 24, 2020 6:31 pm

    [*]Image
    I am still thinking this is a Timing issue ....... You did not mention when I asked about the orientation of the cam lobes (facing front or rear , up or down) , if the mark on the Balancer shaft and the cam are aligned with their marks , it would be almost impossible for the valves to hit ....... There is a exception ......... IF .... You installed or mis timed the Balancer shaft and the mark is aligning to a out of time balancer shaft/gear ......... Then you would be out of time no matter what you confirmed with the cam and gear marks ......... :-k




    Do you have a picture of how it supposed to be oriented and how It suppose to go in I really need help please get back to me thanks
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    JimDirt
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    Re: Intake valves hit piston at tdc

    by JimDirt » Tue Aug 25, 2020 10:41 pm

    It is basically going to be just like the 450R and 250R , so it should look like this below , though the marks will be in different locations , as the round plug marks will be slightly higher , and the cam marks will be on the top and bottom as opposed to level with the head like the 450 , but the same principle applies ..... 13-14 is the marks on the clutch side under the large round plug , you can see the marks on the cam (17-18) ... there is also a mark on the ignition cover in the small round plug , all 3 need to be aligned at the same time , if not , then either the gear slipped on the cam , or you have the timing chain off more than a tooth , depending ... As 1 tooth off the valves should not hit ...... , I do not have a Manual for that bike , so I would suggest either going to your dealer and requesting a Factory Service Manual for it , or you can download one from https://www.manualslib.com/manual/10539 ... =66#manual (the Manual from the Dealer will be around $50 or so , I did not check the price from Manualslib , but they seem to only have the Owners Manual , but it does have the procedure for checking timing)

    Image
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • clint3006
    Posts: 2
    Joined: Thu Oct 21, 2021 2:02 am

    Re: Intake valves hit piston at tdc

    by clint3006 » Thu Oct 21, 2021 3:26 am

    Hi did you ever find the solution to this problem. I currently have the same issue after installing a new piston and valves. All timing marks align correctly and engine turns one revolution but locks on 2nd revolution as I think piston hits intake valve

    Any help appreciated.
  • clint3006
    Posts: 2
    Joined: Thu Oct 21, 2021 2:02 am

    Re: Intake valves hit piston at tdc

    by clint3006 » Thu Oct 21, 2021 4:12 am

    Anyone else had this issue. I have the same problem after a piston and valve change.

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