Topic: CB500/4 K1 backfiring, misfiring at low rpm and dying out when warm

[zipper]

It finally stopped raining and i went thru the ignition carefully with the strobe light i just received with the mail. Its now perfectly adjusted and the engine sounds better than ever. Unfortunately the misfiring issue when warm remains.


This time i got to troubleshoot it a little further, cylinder #2 seems to be the one misfiring and being cold to the touch. What the heck? All 4 cylinders get a spark and the cyl #3 is healthy. The HT lead on the #2 is the one being a little short but the cable seems healthy..

Did i miss something, or is the compression test next? 

PS: i don't have a compression tester

[Deltarider]

This is what I would do.
1. Ask myself if maybe I made a mistake checking and setting the tappet clearance of #2. This must be done cold when the "T" (2+3) mark on the spark advancer is aligned to the timing mark, after inlet valve #2 went down and up again.
2. Check if #2 floatbowl receives gas (just open and close the drainscrew).
3. Check whilst idling in the dark if #2 looses it's spark between the plugcap and the head or between the HTlead and the head. Listening for little cracksounds helps.
3. Get #2 plug out and study the nose. You might change the sparkplug.
All this assuming: the #2 O-ring between inlet manifold and head is in good order and not leaking and the #2 exhaust gasket is in place and not leaking.
4. A simple compression test would be to press a thumb or finger on the sparkplugopening and see if it stays there when a helper kicks the engine (WOT and killswitch off). If you manage to keep your thumb or finger over the hole, compression is not good (I don't expect this to be the case)..
5. Check #2 airscrew and slowjet. You can undo the floatbowl without having to remove the carbs. (I can do it blindfolded, but I have to confess #2 is the nastiest because of that neighbouring clutch cable).

[zipper]

Thanks! I did everything in the list and it's working now. It seems the lead for cyl#2 isn't connecting perfectly with the cap. I managed to get a good contact now, but i need to find a long-term solution.

If i were to solder an extension of the lead on the existing one, is there anything special i should be thinking about, other than being sure to seal the soldering with for ex. silicone?

[TwoTired]

The spark plug cap is supposed to screw into the wire lead and firmly grab the steel core of the wire.  There is usually enough length to cut off 1/8" to 1/4" of its length for the screw post to find firm material.  If the wire has been cut too many times, then NGK makes splicers for the HT leads to lengthen them.

Soldering will just melt more of the insulation.  And when the insulation is damaged, the high voltage will try to jump from the wire to any earthed metal on the bike rather than across the spark electrodes.