Topic: Firing issue

[jwurbel]

Have a 1972 CB 750 K2.  Took advancer apart to lube.  Had previously cut 1/2 loop on springs due to lazy return to idle.  Cured that problem. Put back together but left the ignition on over night by accident.  Dumb!
Went to start and exhaust 1 & 2 cold while 3 & 4 heated up.  Not sure that made any sense.  Tested coils, wires, and condensers.  Didn’t find any issues . Running Hondaman system and went through that.  Pretty sure hooked everything back up correctly. Looking for some help.

[newday777]

Do you have a couple of old condensers to put on and try?

[jwurbel]

I don’t.  But that’s where I am leaning so I ordered 2 yesterday.  Will update when received.

[newday777]

I don’t.  But that’s where I am leaning so I ordered 2 yesterday.  Will update when received.

I hope you didn't order aftermarket condensers.....

[scottly]

Did you swap the #1 and #2 spark plug wires? #1's wire should go to the same coil as #4, and #2's wire should go to the same coil as #3.

[jwurbel]

Condensers ordered from  Yamiya.

Plug wires not swapped but a good point.

[HondaMan]

With the Transistor Ignition you can also just disconnect the condensors (if you suspect them bad) and run it that way. Mine is like that at present.
I normally recommend leaving them in for a couple of reasons: first, if an EMP went off in close proximity it might damage the box (although I seriously doubt it with the low impedance design I used) and then switching back to points would involve just unplugging the box and plugging the points (and condensors) back in, so you can get into traffic again, quickly. The other reason is: almost all of the occasions when someone has contacted me about misfire when the box was (just then) added has turned out to be bad condensors, from China. In just one case, it was due to a cracked female connector leading to one of the coils: it would run OK until the bike warmed up, then sputter.

[jwurbel]

Hondaman,

I am using currently original Honda condensers.  They are still connected with your system.  Awaiting replacements on condensers from Yamiya.  When I tested the originals the numbers were low.

[HondaMan]

Hondaman,

I am using currently original Honda condensers.  They are still connected with your system.  Awaiting replacements on condensers from Yamiya.  When I tested the originals the numbers were low.

Yes, the condensors (of old, until around 2006 or so) lose capacitance when left unused for a long time, like over winter. They are designed as 0.24uF, 400v devices with tolerance of 0.20-0.28uF, and after a long sit in a box or on an old bike in storage they will drop down to as low as 0.16uF, coming back to life after about 30 minutes of runtime and back-in-spec after a couple of heating-cooling cycles.

This is different from capacitors: they stay at tolerance values for decades, but once they go out of tolerance they don't come back in with use. Different critters.