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  1. #1
    skipyurple
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    Default Twin Cam Magneto Question!

    Just put a morris mag on my 02 twin cam and its running ok, just wondering if there is a good way to really dial in the timing even though there is no timing plug/marks on the twin cam engine. I used the count the fins on the flywheel and eyeball method recommended in the morris install manual. Thanks!

  2. #2
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    I wanna bump this. Skippys been trying to get this thing runnin right for the last month. Hard starting, lotta backfiring out the exhaust. Sounds like timing. Feels like timing. How do you time one of these things without popping for the buzz box?

    I talked to the dude at Morris and we had done what he told me to do. We did it again. No improvements. Any tips? Figure we could get it within a degree or two without which is in spec?

    Apparently, the compensator can make it hard to start, but neither of us understands what that does or why it makes it worse. What's up with that?

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    You can cover all the bases by moving the magneto a tiny amount each time. If you cover everything in range, you'll eventually hit the sweet spot if there is one.

    Backfire out exhaust = retarded. Backfire out intake = advanced.

    TDC can be found with a dial indicator down a spark plug hole if you have the sort with the adapter. You can find "TDC tools" on Ebay.

    Since the bike runs, you are in fiddling range anyway. The magneto is presumed good so all that's left is adjustment. I don't overthink simple jobs. They can be tedious simple jobs, but they are still simple.

    The buzz box is reasonably priced compared to hunting parts and building one.
    Last edited by farmall; 09-23-2016 at 5:27 PM.

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    thanks farmall. The point of the buzzbox is so you can see when the points begin to open, which is too small of a gap to see with your eyes, correct? Is there a way to get this right without the box? Feeler gauge? something like that?

  5. #5
    skipyurple
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    Thanks farmall. Can anyone shed some light on how exactly a compensator can lead to hard starts with a magneto?

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    I messed with timing mine, (on a shovel though) for a while, and then finally paid for the buzzer box they sell. I was way off guessing at the moment they begin to open. Yes, it costs like $80, but i'll have it forever. What compensator are you talking about?

  7. #7
    skipyurple
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    The compensator is the smaller drive sprocket in the primary. It has a 3 lobed cam and is spring loaded and I guess it's purpose is to help absorb vibrations from the engine?
    Click image for larger version. 

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    He means an impulse coupling. I've only timed a couple of those style, but I just did it by ear as usual.

    Impulse couplings are designed to wind up then release with intent to boost spark at low RPM. They are intended to make starting easier.

    Found this which is interesting but with a new mag I'd just slowly run through different settings until it starts properly. You cannot not get the same timing if you move slowly enough that you hit the same physical location.

    http://www.jockeyjournal.com/forum/s...d.php?t=175049

    You could build a buzz box (magneto tester info is abundant on the internet) but if owner has magneto money I'd be shitting the cash for the buzz box if you think you need what one does. It's not expensive compared to the mag.

    Disconnected points could be timed with a test light and battery or a meter etc.

    http://www.dansmc.com/buzzbox.htm

    Aircraft use the buzz box for convenience and accuracy.

    Question, is the mag the ONLY thing changed on that bike before attempting start?
    Last edited by farmall; 09-26-2016 at 1:42 PM.

  9. #9
    skipyurple
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    Hi Farmall,

    I did mean the compensator, not the magneto's impulse coupling. If you look at the morris instructions here at the end there's a note about welding up the compensator or replacing it with a solid sprocket. Just wondering exactly why that is. And yes I changed to a mikuni flatslide when i did the magneto should have mentioned that at teh top my bad!

    I just went and took your advice and did some slow tweaking and it seamed to reduce some of the backfiring at start so maybe I just need to fuck with it some more.

  10. #10

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    Quote Originally Posted by skipyurple View Post
    there's a note about welding up the compensator or replacing it with a solid sprocket.
    They are notorious for failing

  11. #11
    skipyurple
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    Ah ha, well thanks everyone for responding. I messed with the mag some more and it's running pretty good now no more backfiring. I guess I was just overthinking the dynamic timing.

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