The 101 Association, Inc.
For the preservation and enjoyment of 1928 to 1931 Indian Scout Motocycles
"You can't wear out an Indian Scout"
 

sealing the Magneto

  • 20 Apr 2016 9:41 PM
    Message # 3974894
    Deleted user

    My 101 likes to sling oil out of the case where the Magneto enters the case. I took the cam cover off and took the mag gear off and there was no seal there. 1 put a small felt washer on the mag shaft and mounted the gear. The gear had a slinger disk spot welded to it so I thought this would work. Well oil is still flying. Walker offers a large felt washer to go on the mag gear but it will not work with the slinger welded to the gear. Should I take the slinger off and use the felt? Or what other options do I have? 

    Thanks for your help 

  • 21 Apr 2016 8:06 AM
    Reply # 3975830 on 3974894
    Tim Raindle (Administrator)

    Dave , felt washer is glued to the mag, and squashes up against the back of the cam case, oil slinger is supposed to be there. Tying a small rag or some hemp string/rope around the outside of that to soak up oil would have been the fix back in the day , when saturated they no longer let oil out :) This worked on jeff Alperins bike on the 2012 Cannonball, I believe he still has the bit of rag I tied there on the bike.

    Is your breather working well ? If the engine breather disc is stuck, you will get excess oil blowing out of the timing case thru the mag gear opening, and maybe the pushrod tubes too, instead of the breather pipe. 

  • 21 Apr 2016 8:22 PM
    Reply # 3976981 on 3974894

    The felt washer is basicly an air filter and also prevents oil from getting out. It is quite important to shield from road dust and water to enter the cam compartment into the engine. It is squashed between the magneto body and cam compartment and about 3-4mm thick and can have roughly the same outer diameter as the mag gear itself. The washer hole is a bit larger than the shaft, no need for it to touch the shaft. The felt quality is not too soft but not so firm that it prevent you from mounting the magneto in proper position.

    The part number for the felt washer is different for the 1928-30 engine and 1931 engine. I suspect the later is denser than the former as the crankcase ventilation changed in 1931 when the air tube was transfered to the cam cover. The full crankcase pressure is migrating into the cam compartment in those engines, and as the pressure is supposed to go out the tube instead of through the magneto hole, that's why I think the washer got denser or even tight for those engines.

    Last modified: 21 Apr 2016 8:28 PM | Carl-Erik Renquist
  • 21 Apr 2016 8:32 PM
    Reply # 3976986 on 3974894
    Deleted user

    Good info guys. One question should I be running a breather disc with a hole in it or solid? If I need one with a hole in it this could be part of the problem. I will glue the felt to the mag and see if that helps. All these Ideas make sense to me. Thanks to all and happy spring!

  • 21 Apr 2016 8:32 PM
    Reply # 3976987 on 3974894
    Deleted user

    PS Carl I will try th felt rope also.

  • 22 Apr 2016 1:46 PM
    Reply # 3978502 on 3974894

    No hole. Never use one with a hole in it. That was only for bikes used in parades or escort service for running slow for a very long time. When the engine is running slow, the pumping effect from the pistons is greater than at higher revulotions. And piston rings can't keep tight so more blow-by is produced. The oilpump also runs slower so less oil is pumped in.

    I can think of 2 theorys what is happening. Either the hole is for reducing the overpressure in the engine to avoid oil leaks from all orifies, OR with the ventilation on the cam case, all oil is pumped out of the crankcase with the strong air flow and a hole in the disc equalise the pressure in both compartments in order to avoid all oil blown into the cam case.

    In any case when the ventilation is at left on the crankcase, a hole in the disc will disturb normal air crossflow through the engine and could starve the crankcase from oil.

    Short story-you need the ventilation to work as designed if you plan to use the bike for normal riding.
    Last modified: 23 Apr 2016 4:08 AM | Carl-Erik Renquist
  • 07 May 2016 12:38 PM
    Reply # 4008105 on 3974894

    Regarding the felt seal, I see that as an antiquated setup at best!  If it does "seal" correctly, all it is doing is keeping dirt out, which is good, and directing crankcase oil vapor into the magneto!  That's fine for the bearings in the mag, but not for the rest of the mag, especially when it makes it's way into the points housing.    I've installed a modern single lip seal into the cam case on my 24 and 31 Chiefs as well as a few X's. I've been running the 24 Chief for 26 years and it works great!  The shoulder on the mag gear is 1.0" od, so polish it up nicely and the seal runs here. Installing the seal in the case will require setting the right side case up in a mill, indicating the center and boring the hole to fit the seal. It's a great set up.  I mentioned this some time ago and George chimed in on my seal idea. He was not a fan because it is virtually impossible to find the exact center of where the mag gear will actually be, after installing the mag and setting the gear lash properly, maybe with a few shims. What I do is find the center of the original hole and work from there. If in the end the gear center is off a bit, it's not a problem, the lip seal can give a bit one way or the other and still seal up perfectly.  I will use my 24 Chief as a tried and true example!  It has worked flawlessly for decades. I did rebuild the engine last spring and replaced the seal, though it looked just fine. Remember too, the mag turns at camshaft speed, which is fairly slow, so it's a low wear seal and well lubricated.

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