Motorcycle Repair: GSX-R 750 Firing, poor conductivity, gsx r 750

Question
Hi, I've got a 1986 Suzuzki GSX-R 750H that has just decided not to fire on cylinder number two it was running fine last week I fired it up for a run and its running on three..put in another coil pack and no change ..there is spark at the plug but the header pipe stays cold?...dirty gas? or mechanical?..there are not foreign noises coming from the motor...any help wqould be appreciated

Answer
Hi Rowland,

With the #2 cylinder spark plug removed and grounded, is an arc present?

The ignition coils fire plug's 2 & 3 together, and plugs 1 & 4 together. If the #3 plug has an arc, so should the #2 plug and vice-versa. If not, investigate the plug leads and caps for evidence of defects.

Plugs and plug caps should be dry, clean, and tightly connected. If not, you could experience flashover- (current conducts over the plug to ground instead of through the plug) a condition caused by grime/dirty plugs.

If the cap is loose, you'll likely experience poor conductivity and maybe no arc at the plug.

If the cap or spark plug is wet water shorting may occur resulting with flashover, etc...

If an arc is present, investigate the carburetor for evidence of varnishing or a spec or rust or other fuel contamination that may be obstructing fuel passages and jets on the #2 cylinder.

Respectfully,
Mark Shively