Finding type of earth on BSA

Already posted this query on the "Other Bikes Page", but thought I would try here as well...I was talking with an acquaintance recently, and he bought a 1967 BSA but it didn' t have a battery. I told him it should be +ve earth, but before he installs the battery he should make sure, as some owners have done the -ve earth conversion. So, if you had a battery and a multimeter, how can you determine if the bike is +ve or -ve earth (ground)?

Coil terminals are marked + and - , just look which way round they are connected, other way is to use a multimeter on the rectifier to see which way it is connected.

singring said:

Already posted this query on the "Other Bikes Page", but thought I would try here as well...

Click to expand...

So can we assume the title should now read "Finding type of earth on a Norton Commando" :wink:

finding-type-earth-bsa-t6910.html

kommando said:

Coil terminals are marked + and - , just look which way round they are connected, other way is to use a multimeter on the rectifier to see which way it is connected.

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I would look first at the rectifier and see which tab is grounded, coils will work any which way they are connected. If the bike still has the original rectifier and the mounting stud is not isolated from the frame, then it is safe to say it is a positive ground. With a modern rectifier, then it is very important to see which terminal is grounded becaus those don't have a mounting stud directly connected to one of the terminals. If the bike has a modern rectifier/regulator, take a close look at which terminal is grounded and be sure of the color code, black is not always minus.

Before plugging the battery in, you could take out the plugs and connect your meter to the battery terminals (witout the battery of course) and give the bike a few kicks, you can then tell by the meter reading which terminal is positive and which is negative.

Jean