R50/2 ignition help needed

Discussion in 'Airheads' started by Monkeyboy71, Mar 7, 2017.

  1. isdt BMW

    isdt BMW [email protected]

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    The weak link is the magneto coil, the internal wire insulation breaks down with age, the last BMW with magneto ignition was made in 1969, so the coil is likely 50+ years old. with your new coil, condenser and good points, you will have a great system for the years to come. Use new wires and plugs also. I have had several new bad condensers over the years, so keep a spare handy. Once you get the hang of any magneto equipped BMW, you will ride it for the rest of your life. Bought my first one in 1976, still have it. Have fun!!
    #21
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  2. grumpyoldbstrd

    grumpyoldbstrd Been here awhile

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    You might like to check that there is no continuity to earth when the points are open. Where the condenser wire joins at that little nut and bolt there is very small stepped nylon washer and a fibre washer to prevent the wires and the points blade spring from earthing through that little bolt. Your photo appears to show some sort of non standard setup.

    Good luck.
    #22
  3. Monkeyboy71

    Monkeyboy71 Adventurer

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    Condenser, coil and new plug wires ordered. Should be here mid-week and I will put them on next Saturday and test 'em out. I will also go through the timing again, check the point spacing, and check the washer set up on the points. I'll be sure and let you know how it goes. Hopefully we'll have a video of her running to share!
    #23
  4. Pokie

    Pokie Just plain Pokie.

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    Make sure you don't waste a lot of time checking that your points aren't grounded (when open) unless you disconnect the condenser.
    #24
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  5. Monkeyboy71

    Monkeyboy71 Adventurer

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    Got the condenser today. Picked up an original one. What's interesting is that it's got a different bracket and it's smaller than the one on my bike now. But I ran the number and they appear to be correct. I would just have to switch out the clamp that holds it because it's definitely not correct.

    http://www.ebay.com/itm/BMW-Condenser-Condensor-R69-R69US-R60-R50-2-Vintage-Twin-/301597300973

    I do plan on ordering a new one, but that process required my attention during business hours whereas this eBay order did not. And, having said that, I just found this "newer" model on eBay and it looks more appropriately sized and mounted.

    http://www.ebay.com/itm/condenser-B...m33c6f80837:m:mvp7bKrSOPqlAkeU2ePf5zw&vxp=mtr

    What I'm still wrapping my head around is how to test the condenser. I have read that it's a continuity test. And while I (sort of) know how to set my multimeter for that, I'm not sure what I'm looking at on the numbers. I'm not well versed in electricity, but working on that.
    #25
  6. tlub

    tlub Long timer Supporter

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    Any old condenser will work. As long as you can get it in a bracket, it will work. I think the 'normal' thing to do is just go to an auto parts store and ask for one for a 351 Ford V-8 from (pick a year they were made). Just sound specific about it so they don't ask a jillion questions and end up telling you they can't help you. Condensers are hard to properly test for function. If they short, yeah they are bad, but as for being able to actually provide capacitance? That is more specialized. Not like a resistor.
    Just buy one and assume it is right.
    But be sure you have it connected to the points properly and you haven't inadvertently grounded the points in the process. Just like Pokie said, but the number of us saying it tells you how easy it is to do.
    #26
  7. isdt BMW

    isdt BMW [email protected]

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    I once bought a Ducati 250 Desmo in nice shape for $100, it wouldn't run, moved the condenser wire to the propped spot and started doing wheelies shifting to second, traded it for a rare NSU Gelendemax.
    #27
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  8. danedg

    danedg Horizontally Opposed

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    Can you post pics of what the "current" coil/ignition setup looks like?
    #28
  9. Monkeyboy71

    Monkeyboy71 Adventurer

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    Quick update: I replaced the magneto coil and got spark right away. I got all the fluids in her, the gas tank in place and will hook up the gas lines and give her a kick this weekend and see what we can make happen.

    Any advice on first time starting a fresh build would be welcome.
    #29
  10. tlub

    tlub Long timer Supporter

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    Two schools of thought. One is run em hard to set the rings. Don't rev high - keep rpm below what it would be around 60-65- but use full throttle to maintain high cylinder pressures and seat the rings. This is like we do for aircraft engines, and it has worked well for me.
    The other is to baby it for 500 miles. IMHO, this promotes non-seating of rings.
    In either case, don't get it too hot, don't over-rev it, and at 100 miles, change the oil and re-torque the heads, and re-set the valves.
    :lurk
    #30
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  11. Monkeyboy71

    Monkeyboy71 Adventurer

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    Alrighty, we're up and running. I do not have the exhaust hooked because the nuts are a little banged up and I don't want to force them on these clean heads. Since they are off, I can see the left side is backfiring, where as the right is not. I say backfiring because it's shooting flames out of the exhaust port. I'm not sure if that's just running rich or if this is a timing issue.
    #31
  12. Monkeyboy71

    Monkeyboy71 Adventurer

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    Calling it a day. Tomorrow I'll go through those steps, @danedg, and tonight I'll watch this YouTube video where the guy sets the timing and re-read your notes.
    #32
  13. tlub

    tlub Long timer Supporter

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    Sounds like differential timing is a good possibility.
    #33
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  14. danedg

    danedg Horizontally Opposed

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    Confirm that you are on the compression stroke for each side. Piston should be "out" . The pushrods will be "in". The flywheel will be at OT. Once you've set the valves for one side, rotate engine 360 degrees. You'll then be at the compression stroke for the other side.

    Hook up your exhaust... make the head connection first, then hang it off the rear...
    #34
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  15. Monkeyboy71

    Monkeyboy71 Adventurer

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    Looks like I also have a soggy float and a subsequent gas leak. We cleaned up the carbs, enough to get it running, but not enough to trust them. So I'll order up some new floats and washers and rebuild those next weekend and then fine-tune the timing.
    #35
  16. Monkeyboy71

    Monkeyboy71 Adventurer

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    We're getting close. But it's still not quite right. I have the magneto perfectly aligned to the static mark on the flywheel. I have the point gap set to 0.16 at it's most wide open. I do not see how to then adjust the points plate to "just barely open" at the static mark, as I've been told to do. But I do have the timing light out and at idle it's running smooth and the timing appears to be good. And it advances with throttle. The big issue that still remains is the back firing on the left side. It's rough and ill-timed on that one side. But the right runs like money.

    What am I overlooking?
    #36
  17. Beamer Bum

    Beamer Bum Been here awhile

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    You might have the dreaded "differential timing." Connect the timing light to the other side spark plug wire. You may have to flip the inductive pickup upside down to get a reliable trigger. One side is a positive spark, the other side is a negative spark. See where the opposite cylinder timing is.
    Alternatively, shine the timing light at the advance unit while running. If you see two images,you have a difference in timing between cylinders.
    #37
  18. danedg

    danedg Horizontally Opposed

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    What am I overlooking?

    When the R60 started doing that it ended up being a bad spark plug (brand new out of the box).
    It had JUST enough spark to fire at idle, but would fail at speed.
    Check ALL connections from the coil to the plug. You should have zero ohms (resistance) from here to there.
    Wire, cap, plug...check 'em all individual and together.
    The Eldorado spits and farts and burps when cold and lonely. It doesn't send enough fuel to the left side until warm. Or until the petcock hits RES. Make sure your fuel lines are arranged to provide positive flow through gravity.
    Liquid doesn't flow uphill.
    And lastly, (firstly?) , fill the tank. Fresh 93.
    #38
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  19. Beamer Bum

    Beamer Bum Been here awhile

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    What Dan said is possible. Sometimes electrical problems are carburetor problems.
    Zero ohms from coil to plug is VERY important.
    And one other possibility is the "Spark Gap" at the coil. There are two little points under where the coil mounts. There should be 11 mm space between the points and where the spark plug wire attaches to the coil. Make sure you don't have a long tail where the spark plug wire attaches to the coil. Too short a gap will cause the spark to jump to the point instead of the spark plug.

    [​IMG]
    #39
  20. danedg

    danedg Horizontally Opposed

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    What causes the spark gap to fire is a failure somewhere in the ignition cycle from the coil to the plugs.
    Too much juice, and it's gotta dump it somewhere...
    #40