SOHC.co.uk Forums > CB350/400
HT Leads on coils
royhall:
Not checked the resistance on the original coils yet, but the pair of Silvers replacements read 3.4 and 3.1 ohms. I am assuming this will be okay as I am running points. Is this correct. Cheers.
gtmdriver:
--- Quote from: royhall on January 25, 2016, 04:14:43 PM ---Not checked the resistance on the original coils yet, but the pair of Silvers replacements read 3.4 and 3.1 ohms. I am assuming this will be okay as I am running points. Is this correct. Cheers.
--- End quote ---
You should be OK with these. The points may burn a little quicker but you should be OK.
AshimotoK0:
Hi Roy. The various four-cylinder SOHC Honda manuals are scant on resistance details referring you to the Honda dedicated electrical tester. The '60's twins manuals were much better on this. Those coils sound Ok to me, I think the cold stall current of the coils should be 3-4 Amps so if you take 12 volts and Ohms low this equates to 12/4 -> 12/3 Ohms = 3-> 4 Ohms (R=V/I).
You have to be careful with cheopo multimeters as the low Ohms range is often not very accurate. The best way of measuring resistance with a cheopo one is to put a known resistor in series with the coil and measure the current through the coil and the voltage drop across the coil. The resistor wants to be about 15 Ohms. You then work out the resistance of the coil using Ohms law R=V/I . Doing it this way you are only passing a lowish current through the coil and minimizing the self-heating, as the coil resistance increases as it self heats. Obviously, if you have an expensive meter (Fluke or TTi) it's not necessary.
Attached is the type of info in the sixties Honda gave.
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royhall:
Thanks for that Ash. Cant say I understood it all though. ;D Take your point about the cheap multimeter. My garage one is a cheapo but I have a fluke on the work van (couldn't be arsed getting it out), so will test them again with that. Will be interesting to see if the readings are different. Will post the new readings later. Cheers.
royhall:
There's interesting, didn't expect them both to be the same. They are both 2.7 ohms on the Fluke, retested on the cheapo and got 3 & 3.3 this time. Think I will bin the cheapo, it was only £3.99p with 10 litres of BP. Does that change them being okay to use on points. Cheers.
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