Home Forums 250 Superkarts slip fitting bearings/crankshaft ?

This topic contains 3 replies, has 4 voices, and was last updated by  Chris Reinhardt 5 years, 8 months ago.

  • Author
    Posts
  • #5982

    nigel cooper
    Participant

    What are some of the ways that are used to make your crank bearings slip fit.I have already installed the bearings so any work would have to be done on the crankshaft.Is slip fitting an “approved” procedure in doing a rebuild?

  • #5997

    Ian Harrison
    Participant

    Hi Nigel,

    We sometimes slip fit the left-hand main, particularly on test engines that might be split frequently. We have a simple jig that locks the inner bearing track whilst we mount the bearing in the lathe and then we seal the bearing with grease. We then spin the bearing counter clockwise, whilst we run a close fitting 120 grit flap-wheel clockwise in the bore at about 15,000 rpm in an air die-grinder. 15 seconds does the trick. Just keep the die-grinder nice and square and move it in and out quickly from one extreme of the flap wheel to the other and it will be very accurate. Then just a quick clean out and it’s ready to go.

    The only advantage for normal race use is that it makes gearbox ratio changes a bit quicker, when you don’t have to remove anything on the right-hand side. Otherwise we just use a crankshaft puller and installation tool.

    Even if you have slip-fitted the bearing or crank, sometimes the dowels take hold, so if your only splitting it once a year you may have to use the puller anyway, then it’s not really of any benefit.

    Best Regards

    Ian :-)

  • #6022

    Bob Baldwin
    Blocked

    What are some of the ways that are used to make your crank bearings slip fit.I have already installed the bearings so any work would have to be done on the crankshaft.Is slip fitting an “approved” procedure in doing a rebuild?

  • #6031

    Chris Reinhardt
    Participant

    Bob, we used to slip cranks on the 1-2-5’s.  The basic concept is to put the crank in a lathe and spin it and use a piece of sanding cloth to trim it down.  Usually all you need is some racer’s tape to hold the rod in place and spin the crank fairly slow.

    Ian’s method of trimming the bearing has become preferable,  probably more accurate, and can be done in a drill press that most all of us have, and if you change your mind or screw up, it’s cheaper to change.  :)

    CR

    Chris Reinhardt

    CR2 Motorsports

    http://www.cr2motorsports.webs.com/

    XV Racing Products

    http://www.xvengineering.com/

    ­­

You must be logged in to reply to this topic.