Motorcycle Repair: cb900c not running right, electronic ignition modules, 4 ohms

Question
Hi Bill, My 1981 CB900c pops and sputters,sometimes shut off.had carbs done twice by 2 local shops,new plug wire caps,fuel tank creamed,starter/kill switch replaced,wiring checked,new battery.since it came home,I checked for spark,getting spark at grounded plugs,noticed plugs #3,4 looked "sooty and lightly greasy". #1&2 showed signs of firing properly.I adjusted cam tensioners.the RPM is revving much better without hesitation and stumbling as much.I've never adj. valves and also checked alt rotor.it's reading 3.4 ohms.not charging correctly until RPM is around 3k or more.still have to leave choke lever out a little to keep running.I've spent toooo much money already. please help!!! I'm ready to ride!  LOL     Thanks, Trent

Answer
Trent, you need to fix the charging system first.

http://www.electrosport.com/technical-resources/known-issues/common-tech-issue?m

With the hi-output headlights and no/low charging, the battery voltage drops down below the cutoff point for the electronic ignition modules, then you get misfiring.

DO check valve clearances and check compression with a gauge, so you know that you have a decent foundation to work from. At his stage, you will be having some oil coming past the valve stem seals now, which will create oil burning and plug fouling in extreme cases.

There is a fuel control system (automatic shut off) that could be adding to your woes, if the diaphragm is failing. Air cut valves need to have good diaphragms too.

Fix the rotor issue first and check to make sure that the rest of the charging system hasn't been damaged by it.  http://www.ricksmotorsportelectrics.com/index.php is another source of a/m parts for the charging system, along with Electrosport.

Bill Silver