N Board Forum - Expanded Thread Page

Subject: Point Gap

[Back] [Return to Top of Forum]

Jack - Iowa    Posted 03-24-2020 at 18:32:21 [URL] [DELETE]        [Reply] [Email]  
  • Point Gap
  • On a 860 how much variance is allowed between the four lobes?

    Thanks,

    Jack

    K.LaRue-VA    Posted 03-25-2020 at 08:32:50 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Point Gap
  • Model or type of vehicle does not matter. Any variance seen when measuring gap at different lobes is usually caused by worn distributor shaft bushings. Point gap specifications are often a range. When distributor shaft wobble allows point gap to vary more than the specified range, it eventually becomes impossible to get that engine to run as it should. Watch point gap while attempting to move distributor shaft side to side. "Too much play" is usually obvious without measuring.

    Jack - Iowa    Posted 03-25-2020 at 08:44:05 [URL] [DELETE]        [Reply] [Email]  
  • Re: Point Gap
  • Thanks Kevin.

    This is a puzzle! Drove the tractor in the machine shed last fall.
    Has not run since! Measure .010 difference! Do not detect shaft looseness. Working on Smart Phone! Will respond again when on computer.

    Jack

    K.LaRue-VA    Posted 03-25-2020 at 11:11:15 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Point Gap
  • The distributor cam should wear evenly (.010 is quite a bit of difference). The distributor shaft might have gotten bent by an overly aggressive rebuild. If it's bent you should see the wobble as it rotates. Even so, it should still fire and run if the points are opening and closing. Check across points with them closed and open with an ohmmeter. Any resistance across points when they are closed may prevent coil from charging and making sparks. I have had a recurring problem where my points keep getting covered with something. Never did figure out exactly what is going on. I've tried three different sets of points, polished like a mirror and the problem just comes back. My coil went bad at one point and I thought that might have been the problem all along. Nope, three weeks later had the same problem. Engine failed to fire, popped cap, polished points, checked gap, put rotor and cap back on, and it fired right up. The only theory I have left is this may have something to do with it being much wetter than normal for the last 2-3 years.

    Jack - Iowa    Posted 03-26-2020 at 20:25:28 [URL] [DELETE]        [Reply] [Email]  
  • Re: Point Gap
  • Sending you an email. Address as above.

    Jack

    Jack - Iowa    Posted 03-25-2020 at 19:16:54 [URL] [DELETE]        [Reply] [Email]  
  • Re: Point Gap
  • Bushing installation ahead!

    Decided to pull the distributor and bring it to Des Moines with me. Once I got it out where I could test the lower shaft, there is plenty of movement there! Could not detect it under the rotor.

    The puzzling thing about this is the timing of it! Back in August I pulled the tractor into the machine shed and did a partial split to change the gasket between the transmission and center housing. Did not do a full split as I was working on gravel. When I got it back together climbed on it to drive it out. Did not and has not started yet. Problem seemed to be spark out of the distributor but not to the spark plugs! Installed new components including cap and rotor. Winter came and it sat. Now is the time to get it running. Now have intermittent spark to No's 1 & 2, Steady spark to #3 and no spark to #4. Checked with timing light.

    Now I'll rebuild the distributor and see where we are.

    Thanks for the help so far!

    Jack

    [Back] [Return to Top of Forum]


    Top