Ignition issue

Posted: Wed Jan 09, 2019 8:47 am

My 1983 cb1000c has a spark issue. The number 1 and 4 cylinders aren't firing all the time. The number 4 fires more than the number 1 but, it is inconsistent. the 2 and 3 cylinders fire reliably. I replaced the coil, wires, and plugs and received the same result. I tested the wires leading from the coil to the spark units and it was not shorted to ground. I then tested the spark units as per the manual and the few tests that were listed came out as expected (good). Now I am at the pulse generator and don't see tests. I pulled the cover and there was a white milky, oil oozing from the cover after removal and I had recently changed the main motor oil so to my knowledge there shouldn't be this funk in the area. After all this fun, could the pulse generator cause just one cylinder and sometimes both to not fire? Can I test the Pulse generator? Where could the white oil stuff have come from, the Pulse generator maybe? sorry so long, I just wanted to be thorough.

Posted: Wed Jan 09, 2019 9:00 am

A bad pulse generator takes out both cylinders together.

Posted: Wed Jan 09, 2019 9:11 am

The white funk is water and oil mixed. Bad Juju.

Posted: Wed Jan 09, 2019 10:07 am

So I will clean out the funk for sure and get a new gasket. Are the spark units likely the not firing issue?

Posted: Wed Jan 09, 2019 10:33 am

After reading through the links you sent Grumpy, you believe the coils need more juice and the other components may very well be just fine?

Posted: Wed Jan 09, 2019 10:46 am

If you haven't already , check the pulse generator air gaps .

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=12060

The factory recommended clearance for the pulse generator gap is .016" - .027" .

I run mine at .012" .

The tighter the gap , the more defined ( better ) the spark .

Uneven or too much gap can cause erratic performance . Logically , more so at higher RPMs .

IIRC , the pulse generators should Ohm about 500 or 550 .

Posted: Wed Jan 09, 2019 11:17 am

Thank you! I will get all this tested and reply. In the meantime, I emailed the guy who makes the coil relay mod to see if he still makes these.

Posted: Wed Jan 09, 2019 12:23 pm

Drain oil again, it never hurts to do another change

Posted: Wed Jan 09, 2019 1:11 pm

I did a small amount of research and was looking for experienced answers about oil. I am using Honda oil but, is this oil different than oil from any auto parts store? I read that bike oil breaks down quicker and wondered if it would be a bad idea to use regular 10-40?

Posted: Wed Jan 09, 2019 1:40 pm

There's no problem using Honda branded oil, other than it being extremely expensive.

You need to be careful using off-the-shelf automotive oil though, many brands include friction reducers in their oil blends and these modifiers will make the clutch slip. They've also reduced the zinc content, which is necessary to keep our transmissions happy. Look for one that carries a JASO MA rating. It's designed to work in our type of bikes, where the engine oil is shared with the clutch and transmission.

I'm a fan of Shell Rotella T4 15W-40. Others will chime in with their personal recommendations.

10W-40 is too light by the way. You need 15W-40 or 15W-50. The 50 will probably serve you better in hot Florida.

Posted: Thu Jan 10, 2019 8:18 am

15-40 diesel

Posted: Mon Jan 14, 2019 12:34 pm

Thank you pd750! one of the pulse generator gaps was way off. I corrected it and the firing issue is solved!

As for the oil, thank you for the great information. I just followed the manual's recommendation for oil but, will change it right away.
Thank you all again for the input!