Bad Ignition Coil vs Bad Spark Plugs

Hello Bike Gurus:

So, stalling, backfiring and sputtering.

Would you chalk this up to Ignition coil or spark plugs, if we are ONLY talking about whether it could BE either Spark plugs or Ignition Coil?

Valves, carbs, bad wires or cap, etc.
Steve

SWest wrote: Valves, carbs, bad wires or cap, etc.
Steve

Only happens when the bike gets warm and some say thats a dead giveaway its most likely the coil. This post isnt about my Kawa. Its about my Yamaha XS650, and the problem happened today, ONLY when it gets warm. Its def not the valves carbs or wire. ALL of those things were redone. New wiring harness, valves adjusted etc. Only the coil and plugs werent changed. The bike isnt getting spark = most likely coil. This photo was taken today. It was 83 degrees in NYC:

Coil sounds suspect, put the multimeter away this is likely an insulation resistance issue. But after plugs, caps, leads and LT terminals clean up / recrimp issues are eliminated .

My 750 had a (one) new coil on it when bought it, 4000 miles later and the other side went awol.

Tyrell Corp wrote: Coil sounds suspect, put the multimeter away this is likely an insulation resistance issue. But after plugs, caps, leads and LT terminals clean up / recrimp issues are eliminated .

My 750 had a (one) new coil on it when bought it, 4000 miles later and the other side went awol.

Yeah Im 9000% sure its the coil mostly because, as soon as I let the bike sit for a bit, it starts right up. The faulty coil does not like warm temps

Precisely. Put the meter away...only after other more usual issues eliminated



"Eliminate all other factors, and the one which remains must be the truth."

Arthur Conan Doyle

JWKZ750 wrote:

SWest wrote: Valves, carbs, bad wires or cap, etc.
Steve

Only happens when the bike gets warm and some say thats a dead giveaway its most likely the coil.

TRUE

JWKZ750 wrote:

Tyrell Corp wrote: Coil sounds suspect, put the multimeter away this is likely an insulation resistance issue. But after plugs, caps, leads and LT terminals clean up / recrimp issues are eliminated .

My 750 had a (one) new coil on it when bought it, 4000 miles later and the other side went awol.

Yeah Im 9000% sure its the coil mostly because, as soon as I let the bike sit for a bit, it starts right up. The faulty coil does not like warm temps

One way to test it is to use a hairdryer to warm up the coil when the bike is cold and see if the problem happens. Ed

In re the hairdryer trick, there are a TON of other symptoms that point to it being the coil, like the backfiring even though the carbs, jetting etc have all been checked. After posting this topic I did a LOT of research and im changing the coil. I bought one a month ago when the problems were so serious, but didnt put it in as it was still Winter, and I wasnt riding the bike (i was riding my other ones). So I will put the coil in and Im sure that will take care of it. I will keep you posted.

Tyrell Corp wrote: Precisely. Put the meter away...only after other more usual issues eliminated



"Eliminate all other factors, and the one which remains must be the truth."

Arthur Conan Doyle

His statement, and yours a bit, kinda confused me. I took it to mean hes saying its DEFINITELY the coil so dont bother checking it. Im I reading that right? Sometimes texting and internet messages can be read a number of ways.

Not familiar with the bike, but If it's got points check the gap and/or dwell before changing any parts. A bad capacitor may cause similar symptoms also.

VTEC wrote: Not familiar with the bike, but If it's got points check the gap and/or dwell before changing any parts. A bad capacitor may cause similar symptoms also.

At this point im pretty sure its the coil.