coil test '80sg

[650mark]

in order to accurately test ignition coils, must they be installed onto the bike in order to include the ballast resistor?

I bench tested a pair of stock coils and they had readings as follow:
both primarys read 1.9 ohms, one secondary read 35k, the other 25k ohms.
book says 1.5 and 15k. are these close enough to book spec to function properly? thanks

[DGXSER]

On the secondary, did you remove the resistor plug caps? Those are 5k ohms each. With both in place on stock coils, you will get 25k. Now 35 is to much and indicates a bad coil. If you had the caps removed, then 25 is also to much and your coil is bad.

The 1.9 is kind of high, but I would run it.

[650mark]

thanks for the help. measurements were done with the caps in place.I have these as backup spares, looks like I need to replace one of them

[650mark]

just out of curiosity, could the caps have increased resistance to the point that the test shows the 35k ohms? do caps wear out and get high readings by themselves? i'm an ignition/electrical noob

[D0wn5h1ft]

just out of curiosity, could the caps have increased resistance to the point that the test shows the 35k ohms? do caps wear out and get high readings by themselves? i'm an ignition/electrical noob

Yes, you should take the caps off and do the test again. If there is corrosion on your caps it will cause an abnormally high resistance reading. From an electrical perspective there really aren't intermediate states of failure USUALLY. They often either short (resistance of 0 ohms or close to it) or they break open (inf resistance, or 1.___ on your ohmmeter).

[DGXSER]

Yes, you do want to pull the caps and test that 35 ohm coil again. The failure could be in one or both caps just as likely as the coil itself.

[motoman]

Yes, you do want to pull the caps and test that 35 ohm coil again. The failure could be in one or both caps just as likely as the coil itself.

With coils removed, can also test across coil connections. The 3ohm coils(81 and later) the 'go/no go' cut-off point IMO is 2.7-8ohms and is indication they are headed 'south'. The earlier 1.5ohm coils cut-off point of accepttance would be realative IMO. IMO, without further testing, that telles me all I need to know.

Plug wires is seperate testing. Coils, plug ends and wires have to be tested seperately to isolate a secondary ignition issue.

[650mark]

once again this forum has proven to be invaluable in terms of solving problems and troubleshooting. after removing the caps from the plug wires I found that the caps read 8.5k and 11.4k ohms. the coil is good and I bought new 5k ohm caps and all is now correct. only cost $10.00 for both new caps and I now have a reliable spare set of coils. neato

[D0wn5h1ft]

once again this forum has proven to be invaluable in terms of solving problems and troubleshooting. after removing the caps from the plug wires I found that the caps read 8.5k and 11.4k ohms. the coil is good and I bought new 5k ohm caps and all is now correct. only cost $10.00 for both new caps and I now have a reliable spare set of coils. neato

Glad to hear it worked out! The single greatest move I made with the XS11s I've owned is get new plugs and wires. I also happened to put dynateks in mine but that's not necessary if your stock ones are working fine.

[650mark]

i'm fortunate that my xs1100 runs like new with zero issues. several of my xs650's had running problems but after installing new, better coils and iridium plugs they all ran perfectly for many miles. thanks again to all for the help.

[skids]

On the secondary, did you remove the resistor plug caps? Those are 5k ohms each. With both in place on stock coils, you will get 25k. Now 35 is to much and indicates a bad coil. If you had the caps removed, then 25 is also to much and your coil is bad.

The 1.9 is kind of high, but I would run it.

I have seen NGK caps from 3 kohms each to 8 kohms. Check your caps. Coils are abot 15 kohm, add ohms for caps. If they are 8 k each, you would get 31 kohms.

One more thing: when coils are bad you can get much higher ohms when hot vs cold.