hello,

I have a K100RS 1984 that will not start. Fuel wise all is OK. Injectors are cleaned, fitted a new fuel pump and all that is working fine.
Switched to the electrical side of the ignition and I see that I don't get a spark on plug 2 and 3.
All spark plugs are brand new.
I am not a electrical guy so I checked some video's on youtube on how to test the ignition coils.
There is see people saying to meausre the resistance between the 2 wires going to the coils but when I do that then I get no conductivity between these 2 connection poins on the coil. Even on the coils that are giving a spark. What am I doing wrong?

thanks, Michel

You probably not doing anything wrong, what you see is very typical of the coils when on their last legs. The secondary coil can be open circuit and it still will run because the spark will jump the gap as it does in the spark plug but when arcing occurs within the coil the insulation gets progressively destroyed then eventually fails.  New coils is the answer but make sure you get the correct coils. 8V and 16V engines have different coils.

OK, thanks.
So at the moment coil 1 and 4 give a spark.
When I connect the wire from coil 1 to coil 2 then that one also gives a spark.
Coil 3 is dead.
So if I understand correctly then you are saying that if don't measure any conductivity between the 2 wires it is truly time to replace even if they give a spark?

thanks for the help.

first off, measure the coils directly ..you may have failed plug leads ???

the coils contact on the secondary (high voltage side ) points are way down deep   and deeper than a lot of multimeter probes can reach  easily

to make my measurements I wrapped some stiff copper wire around the probes to get that extra length , and successfully measure the coils

notice if any of the coils output terminal are discoloured as this can make a big difference , if you find one that is greenish in colour that will give you an indication that the seal of the rubber boots has failed ..or that the connections have been intermittent for a good while  or both have occurred over time

I may add I have 8 coils here and all have the same issues ,of being open circuit ...they may work , sort of , but the damage is done already

whilst doing this testing don't forget to measure your plug leads end to end , don't forget to flex the leads and  notice if any form of intermittent connection exists... they should measure under 6000 ohms on the longest lead for example

note # we often see the plug top (spark plug end ) corroded to blazes  as the ferule that is supposed to be fitted to the plug is missing so the high voltage attempts to jump the gap to the electrode on the spark plug pitting the spark plug lead plug top ..(another likely reason for coil failure in my mind at least

I recon that failing leads adds to the early failure of the coils output voltages and is often overlooked for far too long

good luck

Ok so i that what i say and the result is :

no conductivity on any of the coils. primairy or secundairy

So new coils need to be ordered I guess.

and testing the lead it turns out that 3 out of 4 are broken.

mister_anger wrote:Ok so i that what i say and the result is :

no conductivity on any of the coils. primairy or secundairy

So new coils need to be ordered I guess.

don't forget that on the secondary of the coils your looking for about 10,000  - 13,000  ohms ...so maybe wrong range setting if it set to 2,000 ohms full scale

surprising that the primarys are open circuit   never seen that before , so far

used the correct settings so that was not the problem. They really are dead.

If you need to save some money, you can look for later model '86(?) and up K100 coils.  They had an updated design that was much more reliable than the early ones.  As was mentioned, don't use K100RS4V coils from '91 or '92.

ordered new ones : www.motorworks.co.uk/vlive/Shop/Parts.php?f=b&T=6&Q=12131459513&q=12131459513&NUFilter=15&Filter=submit
and 4 new lead from bsk speedworks.