No Spark

This Just In Joined: Aug 09, 2018 Posts: 3 Location: BC

Hey Guys,

First of all thanks for the add.
Im just cracking into a cb750F and couldnt be more excited. The bikes been parked for a little over a year and was running rough before so ive got quite handful here.

It currently turns over but Im not getting any spark when i test the spark plug against the block while hitting the starter.

Ive tested the pulser coils with a screwdriver and Im getting spark on both sides (plugs 1 and 2). I didnt have feeler guages at the shop today so I wasnt able to check clearances between the reluctor and pulser coils, but since the bike was running before and these havent been messed with Im (maybe wrongfully) assuming that this should still be in spec.

I tested the ignition amplifier and got fluctuation between 0-10v (my battery wasnt fully charged) on both sides of the amplifier unit, and was able to get spark in each side (plugs 1 and 2 sparking against the block) by grounding the corresponding pins from the 6 pin pulser connector.

I have also tested the resistance on the pulser coils from the 6-pin connector and im getting 507 ohms on one and 513 on the other. A little low but still within spec.

I tested for power at the coils (positive end of multimeter at positive connector and negative at ground) and got the same reading as my battery which was a little low +-10v. Im pretty new to using a multimeter so I dont know if this test is really telling anything but thought it might be worth checking.

Ive got the battery on a charge overnight now and Ill re-test the ignition amplifier in the morning with a full battery.

The fact that Im getting spark from the pulsers but not when I hit the starter button seems a little bizzare to me but Im pretty green to this whole situation so maybe Im missing something obvious? A safety switch or something? or possibly a short somewhere in the system?

Thanks guys anything helps!

Burke

Posted: Sun Apr 26, 2020 12:09 am

If your battery isn't in good shape, the voltage gets dragged down when the starter is turning over the motor. These ignitions are a bit voltage sensitive too, so that may be it.

This Just In Joined: Aug 09, 2018 Posts: 3 Location: BC

Thanks for the fast reply!

Okay good to know. Ill test it out with a freshly charged battery and maybe a new battery if I can get my hands on one. Hopefully that sorts things out.

Posted: Wed Apr 29, 2020 8:52 am

Burke,

Any updates on this? I am in a similar situation. My 82 900F ran when I parked it 3 years ago. Did some updates, valve job, new lithium iron battery and regulator/rectifier to suit, I put everything back together and no spark on any cylinders... Actually, sometimes I do get one spark just as I am releasing the starter button. Curious to know if you found anything as I am scratching my head at this point.

______________________

1982 CB900F SS

Posted: Wed Apr 29, 2020 10:24 am

Welcome to the site alero29 ... Smile

Posted: Wed Apr 29, 2020 12:59 pm

Welcome to here alero29 wave

Posted: Wed Apr 29, 2020 1:40 pm

Thanks guys!