Topic: cb550 ignition issues when hot

[nilsey]

I'm having misfiring on 2 and 3 when hot.

The reason i suspect this is because the bikes runs fine cold, gets hot and then stumbles, but then evens out somewhat when i get going fast thru cold air.

pulling plugs reveals 2 and 3 are black, 1 and 4 are ok.

my working theory is that the 2/3 coild or wires are failing when hot.

anyone have any other suggestions?

[Black 750K8]

points

[TwoTired]

3K tuneup check list includes checking the points.
Unusual for a wire or coil to fail with heat alone.  Condenser maybe.

If you have a dyna-s (nothing in your equipment list report), try without the ignition cover.

[nilsey]

yeah, points were replaced recently and condensers as well.

[bwaller]

Did you have the same issues with the old points/condensors?

[TwoTired]

If you swap plugs 2&3 with those from 1&4, do the clean plugs get dark and the dark ones clean up?

[phil71]

recently had a bad dihachi condenser right out of the gate. intermittent, so it was a bear to find, but sure enough, a brand new part was faulty. Not really a surprise with those though, they're not built all that well, and neither are the points.

[Dave Voss]

Although uncommon, the 2/3 coil could have a crack in it that expands with heat, causing a disturbance in the ignition system.  To test this theory, temporarily swap the 1/4 and 2/3 coils to see if the no-spark-when-hot issue moves to cylinders 1/4.  In my experience, coils don't really wear out, but they can become damaged, and often operate intermittently afterward.