XR/CRF 100 Piston Ring End Gap
  • ken.gaal82
    Posts: 4
    Joined: Fri Mar 24, 2017 2:36 am

    XR/CRF 100 Piston Ring End Gap

    by ken.gaal82 » Sun Mar 26, 2017 7:37 am

    Hello again. This time I have disassembled another engine I purchased for $75 and inspected everything. I got to measure the piston ring end gap per the Honda service manual which gives a service limit of .02 for the first two rings. HOWEVER...Mine are at a whopping .086 which I find extremely hard to believe they were worn that much. The engine was smoking pretty badly and had plenty of oil coming out of the exhaust , but still had 150psi compression. So I went and checked another bad cylinder I have with a wiseco 53.5 piston and the ring end gaps were just as bad. So does anyone know if the service manual is correct for end gaps and if so have you seen a ring be 4x the limit on a running engine? Take a look at the attached picture for referance. That is the stock bore cylinder.
    You do not have the required permissions to view the files attached to this post.
  • Back2-2
    Posts: 683
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: XR/CRF 100 Piston Ring End Gap

    by Back2-2 » Sun Mar 26, 2017 8:15 am

    The questions and comments I have are this:
    1. Is the ring gap you are measuring the used rings.
    2. Is the set of rings OEM or aftermarket ?
    3. are you using the piston to push the rings into the cylinder to square up for the measure.
    4. Have you done a indicator check of the cylinder for wear ?

    Comments :
    Yes they or the can be that worn. Both the rings and or the cylinder. From what you described I would not have thought you would still have 150 PSI. But the smoke and oil in the pipe definitely shows oil blow by.
    Neil
    Scottsdale, AZ
    Life without Motorcycles would just be boring, really boring
  • ken.gaal82
    Posts: 4
    Joined: Fri Mar 24, 2017 2:36 am

    Re: XR/CRF 100 Piston Ring End Gap

    by ken.gaal82 » Sun Mar 26, 2017 8:22 am

    Neil:
    1. Is the ring gap you are measuring the used rings. Yes used rings unknown mileage/hours from a 1995 xr100 engine S/N 6400955
    2. Is the set of rings OEM or aftermarket ? OEM from what I can tell. Had an OEM piston in it.
    3. are you using the piston to push the rings into the cylinder to square up for the measure. Yes used the piston to square the rings before measuring.
    4. Have you done a indicator check of the cylinder for wear ? Yes checked last night with snap gauge and vernier calipers. Still seems to be within service limits of 53.1mm. I measured a max of 53.06. No cylinder scoring that I can tell. Im actually wondering if i can get a way with just a new set of rings now???
  • Back2-2
    Posts: 683
    Joined: Tue Jan 04, 2011 3:31 pm

    Re: XR/CRF 100 Piston Ring End Gap

    by Back2-2 » Mon Mar 27, 2017 6:57 am

    Ok - Thanks for the update. Sounds like you got it covered.
    If it was mine, I would start with a OEM set of rings and a piston and check the end gap. If the cylinder is in spec and no damages then that variable is out of the equation. The rings you have could be either completely worn out or maybe not even the correct ones. New set of rings - including the oil ring. See what things look like after you get them. You should look into the valves condition and see what you got also. Valve guides could also be contributing to the burning oil.
    Good luck -
    Neil
    Scottsdale, AZ
    Life without Motorcycles would just be boring, really boring

Who is online

Users browsing this forum: No registered users and 3 guests