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General Category => Yamaha FJ1100 / FJ1200 Running Problems => Topic started by: CycleSmithy on May 30, 2012, 09:26:03 AM

Title: Help! Weak Spark on all cylinders '84
Post by: CycleSmithy on May 30, 2012, 09:26:03 AM
Newby here.  Just aquired a non-running '84.  Went through carbs so now runs but touch throttle & dies.  Spark weak on all 4.  Can spark own finger when cranking and barely bites.  Have a new battery but still very weak spark.  Any suggestions out there greatly appreciated.
Title: Re: Help! Weak Spark on all cylinders '84
Post by: SlowOldGuy on May 30, 2012, 01:35:18 PM
I don't think these ignition systems give a big blue spark.

If you touch the throttle and it dies, then the idle circuit is still dirty.  How thoroughly did you "go through" the carbs?  Full disassembly or spray out the float bowls?

DavidR.
Title: Re: Help! Weak Spark on all cylinders '84
Post by: FeralJuggernaut on May 30, 2012, 10:52:04 PM
Check/Clean the bottom of the coils where they mount onto the frame.  Also inspect/clean the ground wire from the battery to the bottom of the motor.  May also consider a 'new' ground between the battery negative and the frame at a convenient bolt.  I used the airbox mount bolt.   All of that typed; I tend to agree with that SlowOldGuy about fueling issues before spark based on your description.   FJs in general are somewhat cold-blooded and I use a fair amount of choke on first start of the day.  You didn't mention that...   Patients and report back often!  Air filter clean?  any carb boot air leaks?