I've just posted about my recent purchase of a 1973 750 Hi-Rider. I've got it in the shop, up on my lift and am starting some preliminary troubleshooting of a no spark issue. Have pulled up a wiring diagram from this forum and have to ask, am I reading these diagrams wrong or do these bikes have a positve ground, and do they, in fact have a 12 volt system? Help please.
1973 Hi-rider no spark
- Thread starter quawk
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Not quite sure about your response, but does it mean that they are 12 volt, but with positive ground. When you state unmolested do you mean that some are modified for different voltage and negative ground?
texasSlick
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Unmolested = original condition which is positive ground (earth) and 12 volts.
Slick
Slick
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The standard ignition coils, however, are 6V and work through a ballast resistor for the original points ignition. If the points ignition has been replaced with electronic ignition then the coils are connected in series and the ballast resistor is not used.
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All Commandos, yes.
Well that's how it was. Triumphs were also positive earth/ground before 1979. It is possible to convert to negative ground but it's just a matter of getting used to it.
Thanks for the info and background. Now on to my no spark problem.
marshg246
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In my lifetime in the US many vehicles were positive ground. Most companies started the switch to negative ground between the mid 50s and late 60s. Norton, Triumph, and BSA were all positive ground.
Also, many were 6-volt until around 1966 (don't know for sure) but my 1966 Triumph was and my 1967 was 12-volt. I believe that all were 12-volt at least in the late 60s and in all of the 70s.
So, in this community, negative ground is the oddball.
texasSlick
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Positive ground was used in Gr. Britain for many years because it was found there was less corrosion of terminals. This was mainly an effect of the older cloth wrapped wire harnesses in high humidity environments.
With modern harness materials, the corrosion was reduced or non existent, thus the "oddball" ground polarity was eliminated.
Slick
With modern harness materials, the corrosion was reduced or non existent, thus the "oddball" ground polarity was eliminated.
Slick
If the bike has not run for a long time, the place I would suggest to start is whether the points have corrosion on them. This can easily cause enough resistance to result in no spark.
First thing I suggest is to put a voltmeter across the points with ignition on and, with points open, check that there is 12 volts across both sets of points. If no voltage, then problem is elsewhere.
If voltage then I would suggest you very lightly file the points with a points file, without loosening them. (If you loosen them, the timing will change). Although many people recommend against using a fine emery paper because grit embedding in the points can cause open circuit, I have used emery in the past in a pinch and then checked that with points closed, there is zero resistance across the points
Dennis
Vancouver
First thing I suggest is to put a voltmeter across the points with ignition on and, with points open, check that there is 12 volts across both sets of points. If no voltage, then problem is elsewhere.
If voltage then I would suggest you very lightly file the points with a points file, without loosening them. (If you loosen them, the timing will change). Although many people recommend against using a fine emery paper because grit embedding in the points can cause open circuit, I have used emery in the past in a pinch and then checked that with points closed, there is zero resistance across the points
Dennis
Vancouver
Thanks, got it. Being born in the 50s, what I meant to say was in my adult lifetime, so as you said, from about the mid sixties forward, most vehicles in the states were 12volt negative ground. I do have an old Farmall tractor from the 40s that is 6 volt positive ground. But I will now remember: Norton = positive ground (earth, as other parts of the world refer to it as). Back in some of the elctronics courses I took long, long ago, there was discussion/argument about which direction, theoretically, electrons moved, either positive to negative or vice versa. Guess that disussion is better left to the scientists/engineers/geniuses, and in practice, ciruits can be made to work either way.
I've used emery with mixed results. I'm back to using a points file now.
Too bad, as the folded emery seemed to do the job so nicely and easily.
The problem with emery is that most or possibly all Emery paper uses Alumimium Oxide for the grit material. Aluminium Oxide is a wonderful insulator.
After using Emery paper on my Vincent (Norton) points a few times I eventually made it into a hardstarter then a nonstarter.
The points file brought it back to life.
Glen
Too bad, as the folded emery seemed to do the job so nicely and easily.
The problem with emery is that most or possibly all Emery paper uses Alumimium Oxide for the grit material. Aluminium Oxide is a wonderful insulator.
After using Emery paper on my Vincent (Norton) points a few times I eventually made it into a hardstarter then a nonstarter.
The points file brought it back to life.
Glen
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In other posts and in the wiring diagrams I've looked at, it says these bikes, at least if original, use 6 volt coils with a ballast resistor. This bike does still have its' points ignition and I assume is original. Are the coils, if original, marked in some way as being 6 volt. Have also found in other posts here on the forum, it was common for the hadlebar contol switches to have been swapped side to side, either by owners or even at the dealer. On my bike, the right side handle bar switch control has a three position toggle/thumb lever switch that I assume is the kill switch. I also assume the middle position is run, and when switched to either the up or down positions, those are the kill/off positions. Does that sound correct or normal. The left side handlebar control switch has a two position toggle/thumb lever switch, which I assume is the hight/lo beam switch for the headlight. Does that also sound right. These controls are not marked as to the switches functions and I don't have a manual for the bike.
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Is there a 17M6 stamp on the base of each coil?
I'll have to get out to the shop to look and see.
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Yes, if you go into it too far, you find that nobody is even sure what an electron is, so it’s maybe a bit pointless arguing that “electron flow” is more valid than “conventional current,” on an old bike.
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No, the bottom button on the right cluster should be the kill switch.
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