atocp Posted September 23, 2009 Share Posted September 23, 2009 Hello all, Its been a little while since I last posted here. I've had scaffolding in my garage, so not much room to work on my bike. And I also just started back to university, so it's been a busy time. But I have finally gotten round to trying to fix the ignition problems with my yb100. I have decided to fit new contact points. Although the old ones's dont look bad, I have new ones, so they may as well go on. This is where I have hit a brick wall. When I refitted the magneto, I tried to set the timing using an electric voltimeter (and screwdriver for TDC). But before I even got to setting the points, I have a problem. The contact points don't open, at all. When I set the screw holding the points to the plate at its leftmost, they don't open, nor do they when I set it to the rightmost. Or anywhere in between. What actually causes them to open? Is it a static buildup? Or is it simply pushing them open as the magneto spins past. I can't quite figure it out, because I can't see what would physically push it! Another thing is the Haynes book of lies tells me that the voltimeter will 'deflect' just before it reaches TDC, just as the contacts open. But what would happen on a digital one, as there's no needle? Any help is much appreciated Atocp Link to comment Share on other sites More sharing options...
jebb Posted September 23, 2009 Share Posted September 23, 2009 Sounds like you have the wrong points; they are opened and closed by a cam on the inside of your flywheel. Check them against the ones you took off. Link to comment Share on other sites More sharing options...
atocp Posted September 23, 2009 Author Share Posted September 23, 2009 Hey there, thanks for the speedy reply. I bought the contact points as a direct replacement, and they seem to be exactly the same. I was looking here http://www.dansmc.com/points1.jpg at the image and I think i understand it. The cam spins round, and pushes the cam follower up, opening the points. Is this correct. If that is the case, is the cam on the inside shaft of the magneto, or is it a separate element, as the inside of the magneto seems to be very smooth!! This use to work with the last contacts, so I might have to put them back on and see if they open. If it is cam or the new contacts. Thanks again. I shall go out and check it all now. Atocp Link to comment Share on other sites More sharing options...
atocp Posted September 23, 2009 Author Share Posted September 23, 2009 Hi there, Cheers Jebb for the help. I have managed to get the contact points opening. It seems the contact points wouldn't 'reach' down far enough to be pushed. So after a little force, and a tightening of the screw, it seems to work. Next question is, should top dead centre be when the contacts are just opening, at some point while they are open, or when they are at there most open. I would imagine as long as the points are open, and there is a spark, it doesn't matter, as the piston is close enough to TDC, but I was curious as to what it is meant to be. Again, the help is very much appreciated. atocp Link to comment Share on other sites More sharing options...
YPVS TONE Posted September 24, 2009 Share Posted September 24, 2009 Hi there, Cheers Jebb for the help. I have managed to get the contact points opening. It seems the contact points wouldn't 'reach' down far enough to be pushed. So after a little force, and a tightening of the screw, it seems to work. Next question is, should top dead centre be when the contacts are just opening, at some point while they are open, or when they are at there most open. I would imagine as long as the points are open, and there is a spark, it doesn't matter, as the piston is close enough to TDC, but I was curious as to what it is meant to be. Again, the help is very much appreciated. atocp Link to comment Share on other sites More sharing options...
YPVS TONE Posted September 24, 2009 Share Posted September 24, 2009 On the YB100 the points should be just starting to open at 1.8mm BTDC (befrore top dead centre) so you really need a dial gauge and adaptor screwed into the spark plug hole to do this accurately .Tony. Link to comment Share on other sites More sharing options...
atocp Posted September 24, 2009 Author Share Posted September 24, 2009 Cheers Tony for the advice. I shall pop buy machine mart or the likes tomorrow. My fear is that even with the gauge, im not going to get the contact points accurate enough as it's fiddly trying to use the .356mm gap thingy as TDC is reached. More high quality tool naming there, you can feel the professionalism in my motorcycle engineering skills here. Is it also worthwhile to save time, once the timing is finished, to mark the magneto with a score to show where exactly where TDC is, on the magneto and back plate? As that point is never going to change. Cheers, atocp Link to comment Share on other sites More sharing options...
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