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So I’m stranded cause my ATU. advice needed

Discussion in 'The Garage' started by Chrispy, Dec 2, 2020.

  1. Chrispy

    Chrispy XS650 Member

    Hello gentlemen,

    so my engine cut out while riding. I pulled off and started troubleshooting and found that the nut on my advance had come off and been rattling around in there and bent the stop tang on one of the weights. So I’ve probably been riding around without advancing. Felt fine right before, not lagging or anything. What are the effects of not advancing? I feel like I holed a piston or something. I’ve tried to kick it up and she isn’t even trying. Aid me great ones.
     
  2. XSLeo

    XSLeo XS650 Guru Top Contributor

    I doubt you holed a piston. That occurs more from to much advance and low octane fuel.
    If yours is not damaged where the notch for the pin goes You might with a bit of heat, straighten the plate so the pin is straight.
    The nut goes on one way. I don't recall right now which way is right. But it need to be very tight. You can see what happens if it isn't.
    If you can't straighten out the bent pin you need a replacement.
    From what I've read the one Mike's sells is usable. His replacement springs are a bit too long so I would assume the ones on his ATU are too.
    If the ATU you have isn't working right then the idle timing will be far enough of the prevent it from starting.
    Have you read up on the GN 250 ignition mods. There is a 50 some page thread on it. It was originilly for swapping into a TCI bike. They are trying to figure out just how to mount a magnet and sensor on a points bike so it can run ths GN 250 box. If they get it worked out you might wan't to try one.
    This would let you remove your points, advancer and the rod leaving it empty under those two covers.
    Leo
     
  3. Jan_P

    Jan_P XS650 Addict

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    Try to Keep cool
    Riding with no advance can theoretically do bad things
    But please give info

    . " I’ve tried to kick it up and she isn’t even trying. Aid me great ones."

    Is that as in not turning over at all --- or not igniting at all.
    How did this happen . It wont happen to blow a hole in a piston out on the road not noticing it
    Nor blowing both at the same time out on the road not noticing it .--- It would run on one cylinder.

    Guessing --the advance has stuck in advanced high rev position not the retard position that will be normal for startup
    I cant remember since I have Boyer but if you by hand turn the advance to retard and try to start I believe something will happen.
    Most like purr like a kitten on both cylinders . Fuses ?? Checked ?? Battery connection loose ???
    Pictures is always Nice
     
  4. Chrispy

    Chrispy XS650 Member

    Thanks guys, you’re right I did need a little breather. Let me try and be more informative. So the engine cut off while holding about 3.5k rpm. No noise or anything weird just off. She will turn but there is no ignition. Occasionally just backfires incredibly. Battery connection is good. Literally yesterday I lost my positive terminal screw while riding so that’s the first thing I checked. All good.
    The advance got stuck in the closed position. I have delicately bent the stop tang back where it belongs. It works about as well as it did before but is not wanting to spring back all the way.
    Its a 78 with stock points and advance. Single fuse which seems fine. Voltage drop when key is turned so power is flowing. Bike desperately needs a rewire so electrical issues are definitely suspect.

    Something that occurred to me is the only time I’ve heard her backfire like that is when I put the advance rod in 180 degrees off. I’m investigating the advance rod now. Could something have happened with the disk for the advance weights since the nut was off that would invert the timing? Seems like that would require a miracle of physics
     
  5. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

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    Did you take the advance assembly off of the right side to make sure it is still properly aligned onto the advance rod? Something similar recently occurred on a newly acquired 73 I bought. Read about it here: http://www.xs650.com/threads/advice-from-you-ignition-gurus-points-specific.58727/

    When my advance assembly came loose it sheared the alignment pin and thus rotated on the advance rod. Timing was then all screwed up and bike woud only backfire. Once fixed and retimed, ran great again.
     
    Jan_P likes this.
  6. Chrispy

    Chrispy XS650 Member

    Both locating pins appear to be okay. Pulled both out and inspected. Advance unit is secure on rod. Although just to confirm, both locating pins are supposed to face the same direction correct? I never made note of it before and the longer I look at it the less I can remember
     
  7. Jan_P

    Jan_P XS650 Addict

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    2XSive above has something too check above
    Other
    So assuming the positive is connected I Would suspect the Other side ..The negative is loose
    Not necessarily at the battery .
    The reason is that if I recall right a stock Point setup can be viewed as two separate circuits
    two points and two coils : And your machine is not running on any cylinder ( ?? Right )
    Do you have a voltmeter ( or a tests bulb ) a check that there is 12 V at the points is a good thing to do.

    But 2XSive first since there are a known fault there
     
  8. Chrispy

    Chrispy XS650 Member

    Machine is running on 0 cylinders. I do have a multimeter so I will check that the points are live.

    I should also mention that a very nice lady got me and the bike home so I am no longer stranded. Am troubleshooting vehemently in the garage
     
  9. Jan_P

    Jan_P XS650 Addict

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    If you have 12 V there at the points then please follow the ground wiring downstream all the way back to the battery ..tightening up ..perhaps grind with carborundum paper if rust and dirty and some grease .I Use copper grease
    And please come back we reevaluate
     
  10. XSLeo

    XSLeo XS650 Guru Top Contributor

    I don't think it's a battery issues.
    On the advance rod both pins should point the same way.
    Without the engine running manually open the weights on the advancer and release them. The weights should snap back to the closed position.
    If they don't I would suggest pulling the rod out of the cam and cleaning it off as well as cleaning the hole through the cam. A moly grease is what Yamaha suggest as a lube. Some chassis lubes have moly in them. You can find them in tubes for your grease gun. Works well to grease the swing arm and anything else that has a grease fitting.
    Once you give the rod a thin coat and packed the grooves in the bushings in the cam full of grease put it all back together and retest the weight snap back. If it still won't snap back but turns easily with your fingers it may be the spring tension. Their are two springs on the advancer, one for each weight. Take one off. Mark it with a sharpie. This is so you can tell which spring is which.
    Now cut the loop off one end of the spring and bend up the next turn of the spring for a loop. Reinstall this spring. Retest the weight snap back. Often clipping just one spring is enough. If not remove the opne you have not clipped yet and cut off a loop and bend up another and reinstall and test the snap back. This should fix it.
    Once you get the snap back right check the timing at idle with a timing light. Check both sides. If they are both good then slowly rev the engine while watching both the tach and timing marks. This can be tricky.
    Watch the way the timing mark on the rotor moves toward the left. It should reach just too the full advance mark on the stator without going past it. It should do this at about 3000- 3200 rpm. If it does your golden. If it goes past the full advance you will have to retard the timing enough so it doesn't go past the mark. This will change the idle timing some as well. As long as the idle marks don't go below the lowest timing mark it's ok.
    Their is a thread on here somewhere that better explains this procedure. I just don't know where. It's probably up in the TECH section.
    Leo
     
  11. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

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    20201202_195903.jpg Here is a photo that shows proper alignment.
     
  12. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

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    The clymer manual also has a good/simple write up on how to set timing, including advance.
     
  13. Jan_P

    Jan_P XS650 Addict

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    Bare with me if I am wrong on this 15 -20 years since i had points but is it not possible to grab the weights by hand and carefully pull them out and observe if it moves freely + snaps back ..if the point cam is in the right place. ?? Carefuly
     
  14. GLJ

    GLJ Never go faster than your guardian angle can fly. Top Contributor

    Pics didn't happen if no pics.:p
     
    Jim likes this.
  15. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    yes, that is a way to determine if the springs have good tension.........if they snap back firmly all is good, if they are slow, or when they re-seat, and there is a slight gap, the springs are not up to tension and the advance will advance to quickly
     
  16. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    There's 3 pins. One on each end of the advance rod, and one setting the alignment of the housing on the camshaft. The one on the cam is the one 2XSive is referring to.
     
  17. 2XSive

    2XSive At least one screw loose behind the handle bars XS650.com Supporter Top Contributor

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    Yes, should have been more clear in my first post. I suggest completely removing your advance assembly (the weights/springs, disc, then the big nut that requires a punch and hammer to remove, then your backing plate. Check to ensure your backing plate is properly centered over the alignment pin in your camshaft. Mine had sheared that pin off and had spun on the camshaft, thus throwing timing way off.
     
    Jim likes this.
  18. Chrispy

    Chrispy XS650 Member

    Oooohhhh there is a pin that holds the whole advance assembly to the rod? Man I had no idea. Alright I’m checking it out now. Any advice for disassembly?
     
  19. Chrispy

    Chrispy XS650 Member

    I’m guessing the pin is supposed to go where that empty hole full of metal shavings is. Is it supposed to be stuck in there after the nut comes off? I’m guessing not
     

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