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[Help] with my '73 DT3 250, having ignition issues
- flyby987
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Replied by flyby987 on topic [Help] with my '73 DT3 250, having ignition issues
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- RT325
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Replied by RT325 on topic [Help] with my '73 DT3 250, having ignition issues
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- RT325
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Replied by RT325 on topic [Help] with my '73 DT3 250, having ignition issues
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- 19stuberd
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Replied by 19stuberd on topic [Help] with my '73 DT3 250, having ignition issues
So I took the bike back to the lab with the oscilloscope and got some real readings this time, both with points covered and uncovered. Everything seemed to be in the right approximate voltage range and everything, even on kick. One thing that I noticed, however, is that every time I've made spark I've been doing one thing: I have been cranking the flywheel in reverse. Even at the lowest speeds I now have a nice hot spark when I'm cranking in reverse with a drill, but it occurred to me that the kickstarter spins the engine in the opposite direction and that's the way that the engine actually runs. I thought that maybe the voltage on kick was just too low compared to anything the drill could produce, but the readings show that the voltage on kick is just as high as the voltage from spinning in reverse with the drill. I tried spinning it in the normal direction (hard to do without loosening the nut) and sure enough even at the highest speeds I have no spark.
So my question is what could cause the spark to work in one direction but not the other? I feel like it's probably something obvious. Hope to hear from you all soon!
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- 19stuberd
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Replied by 19stuberd on topic [Help] with my '73 DT3 250, having ignition issues
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- MarkT
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Replied by MarkT on topic [Help] with my '73 DT3 250, having ignition issues
As simple as these systems are, there is a lot of engineering and maybe a little "magic" that makes them work.
And as I've said before, it's kind of rare for a source coil to be bad unless it's shorted or open... ohm reading just needs to be in the ballpark. I have one bike with a pretty crunched coil and it sparks great. Usually it's dirt points... sometimes a bad condensor (which technically IS a capacitor... so you weren't wrong calling it that)
Anyway, the only thing that comes to mind is a question... is it possible you re-would the coil in the opposite direction from the way it was wound originally? All the details of how the wire is wrapped around the core make a difference in polarity, etc.
That might not be the answer... but I know the direction and the way the coil is wrapped is important to the way voltage is generated when each pole of the magnet passes by. And then there the "timing" of the voltage peak NEEDING to coincide with the moment the points open.... if coil is wound differently it would still make voltage but timing of when the peaks occur could be different...
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- RT325
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Replied by RT325 on topic [Help] with my '73 DT3 250, having ignition issues
One more important thing when this is sorted. Be VERY sure the flywheel nut is TIGHT. If it'll unscrew spinning it with a normal drill [not hammer drill] then it's not tight enough by a long shot. Hopefully we'll hear it runs soon. Best of luck.
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- Ht1kid
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Replied by Ht1kid on topic [Help] with my '73 DT3 250, having ignition issues
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- 19stuberd
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Replied by 19stuberd on topic [Help] with my '73 DT3 250, having ignition issues
Also with respect to the timing-- I am pretty sure that I set it BEFORE top dead center. I positioned it at TDC and then rotated it CLOCKWISE until it was at 2.8mm. To clarify as well, bike has quite good spark spinning CLOCKWISE and zero spark at all speeds spinning CCW.
Also I will make sure that before I finish this up I will give it a good proper torquing on there. Will update, any other thoughts appreciated, thanks again for everything!
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- Ht1kid
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Replied by Ht1kid on topic [Help] with my '73 DT3 250, having ignition issues
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