The 101 Association, Inc.
For the preservation and enjoyment of 1928 to 1931 Indian Scout Motocycles
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Checking Bosch DVAR Carbon Brushes on a 101

  • 12 Jul 2023 11:24 AM
    Message # 13226863

    (1) I may be just complaining out loud here but maybe I'm also missing something.

    When my '28 101 would no longer start I did what I have never bothered to do before -  check the magneto brushes!  Indeed, one was completely worn away so I replaced both with new. Easy to do on a Splitdorf NS2.

    Now my '31 101 (from Europe - I'm in U.S.) with a Bosch DVAR is having ignition missing and getting hard to start so naturally I wanted to check the magneto brushes. If they are anything like the ones in a ZEV they would be rather short (5mm diam, 8.75mm long beyond spring) and must have short lifespans.

    I found the front DVAR pickup impossible to remove as the screw is directly behind the 101's front left tube and the rear one is close to impossible to reach even with my bendable screwdriver. So I will have to remove the magneto just to check the brushes - something I was not planning on doing until winter cold. Its good I am waiting for delivery from Europe any day now of a DVAR I just had rebuilt.

    (2) Its been many years since I replaced a magneto. Can someone suggest the best flywheel and cam position to impose the maximum rotational pressure on the timing gears to help hold them from falling out when removing the cover?

    Thanks,

    Bob

  • 14 Jul 2023 5:12 AM
    Reply # 13227723 on 13226863

    Brushes needs to have the right hardness in order not wear too fast or score the contact rings. In the DVA magneto there is 3 brushes, one behind the points block. You could have a fourth one in the bakelite lid cover if the mag was equipped with that, for the killswitch. Hardness comparement should always be done with new bought replacements or homemade ones as well. Manufactures have numbers of the hardness but a rough comparement could be checked by scribing a line with the brush on a hard white paper and compare the colour and width of the line with the replacement. In doubt, rather use softer than harder brushes. It is always easier to replace the brushes than replace the contact rings. Retaining springs is important as well, local overheating can make the thin wire gauge springs soft. It is hard to mention some numbers, I have most measurements but not brush sizes or spring ratings. Pictures from the article:

    Restoring a Rotating Armature Magneto [Re: Magnetoman]

    John Healy Online content

    BritBike Forum member

    Years ago BMZ Bayerische Magnetz├╝nder GbR had all replacements for the DVR but I don't know now.

    And a picture of the regulator function from another article.

    5 files
    Last modified: 13 May 2024 4:02 AM | Carl-Erik Renquist
  • 15 Jul 2023 4:19 AM
    Reply # 13228200 on 13226863

    Hope this may help and hope you can open it . Ken


    1 file
  • 12 May 2024 9:14 AM
    Reply # 13355652 on 13226863

    Continuing with information in case anyone needs it in the future ...

    "Can someone suggest the best flywheel and cam position to impose the maximum rotational pressure on the timing gears to help hold them from falling out when removing the cover?

    I'm answering my own question here because I think replies to my other questions in my post did not address this.

    Vahan Dinihanian suggested recently to place the rear piston at TDC when removing the cover. I did that and found all the gears nicely snug.

    Another suggestion for help from someone:

    After removing the oil pump, screw in long threaded screws in the oil pump screw holes in the cover (best: custom made with T handles) until they gently reach and apply pressure to the cam gear inside. Then turn more slowly & gently and this will aid in pushing off the cover while holding the cam gear in place. I haven't tries this but maybe next time.


    Last modified: 12 May 2024 9:15 AM | Robert Lodge
  • 13 May 2024 2:29 AM
    Reply # 13355827 on 13226863

    Mount and demount cams and position them is not at all difficult, so no need to be afraid of pulling gears with the cam cover. It is just a matter of using the right techniqe.  I show that in the picture. Sorry about the dirty engine, but it is not mine, I have mine in pieces so couldn't easy photo that.

    When you are about to put the cam gears in, with the gearbox in third, just a little pull or kick on the rear wheel will rotate the crankshaft just 3 or maybe four cogs anticlockwise. Calculate what position the cams should be in and cams click in easy because both valves are closed with no valve spring pressure on the cam rockers at all!  

    I don't know why the factory did put the markings in that stupid way they did, just 3-4 cogs earlier and no one would ever have problem to mount the cams! I show the factory markings in green in the picture and the red position is where no spring pressure is affecting the cam rockers. It can be a few tries to see when cams and pinion line up, but there is no problem to take out or mount the cams when just turning the crank a few cogs anticlockwise!

    When cams are mounted, rotate the crankshaft forward until markings line up, click in the idler gears and line up magneto gear...easy peasy!! 

    I painted dots in the new position on my pinion and cam gears just to make it easier to line up.

    1 file
    Last modified: 14 May 2024 8:47 PM | Carl-Erik Renquist
  • 13 May 2024 3:05 AM
    Reply # 13355833 on 13226863

    When mounting and line up the magneto gear, be aware that the mag gear could have been replaced, or the DVAR magneto could have been replaced and it is not at all certain that the round key is drilled at the same place, it can differ one or several cogs! It looks like the key is drilled by hand from the factory!

    So I show in the picture the position the breaker should be in when pinion, cam gears and idler gear markings is lined up correctly (don't rely on the magneto gear marking!) 

    Mag gear is mounted with the round key on the shaft because there is no use to reposition the gear differently on the shaft. Turn the magneto gear until the breaker is in the shown position and click in the last idler gear in position, then check if the mag marking is correct.

    Mount and lock the breaker ring in max advance position and check the ignition timing preferably with a indicator clock, right on the piston top on both front and rear piston, a difference in timing indicate a worn timing ring on the DVAR. Replace the ring or divide the discrepancy between cylinders. If the mag gear marking does not line up, grind off the old and grind in a new marking for the future.

    Breaker rings for the Indian is often marked with a stamped "I" under the outer band clamp, but unmarked or with other markings can have 45, 50, 90, 170, 180 degree division, or might be for a single cylinder bike.

    Original grinding of the breaker lift ramp is elaborately done in 2 steps and can be reground but only by an expert with exactly the right size stone to get the right cam ramp for lift speed, I have seen repro rings that will destroy the breaker in short order.

    Usually the adjusting range between min. and max. on the ring is too large, so when max advance timing is set at the stop, the max retard is way after top dead center, it should be at, or max a couple of degrees after tdc. This can be fixed in different ways, make a stop for, or lenghten the adjusting arm, or restrict the slot length on the backside of the breaker ring, or put a stop clamp on the free portion of the handlebar wire. Running the motor with ign. after tdc is not good.

    Don't be tempted to run max advance timing without a stop, attemting to hear or feel enough advance timing, because it is not always felt or heard that the motor has a too advance ignition. I fried an engine like that with too advance timing.

    If you want to experiment, adjust the max advance stop in small increments and check ignition plug colour (can be difficult to see colour differences with the new kind of fuel in the pumps), cylinder temp or other tests instead of only rely on butt feel or sound.

    1 file
    Last modified: 14 May 2024 9:06 PM | Carl-Erik Renquist
  • 13 May 2024 5:00 AM
    Reply # 13355846 on 13226863

    Hey guys,

    as I'm from Germany I'm used to work on Indians with a Bosch magneto and for me it's easier to loosen the rear chain, loosen both engine mounts and put out the spacer at the front motor axle and then you can lift and pull the engine inside the frame for a view milimeters and that's enough to pull the brush holder out of the magneto case.
    For me it's just easier than to remove the whole magneto.


    All the best
    Manny

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