Keep dropping 1 spark plug .....

[SITH]

Hey all ,
I have a 1998 GSXR 750 ... SRAD. EFI
I run NGK plugs, and she has done 32000km

now the problem ... every 1-2000km the spark plug on the fourth piston dies. I pull the plug and it is black !!!
She will run like crap back fire and shudder and it nearly always happens when I am no where near home. I replaced all plugs 2500 km ago because number 4 died.
1200km later number 4 dies again ... so replaced just that one plug and she ran sweet.
Today on the way home the number 4 dies again .... so in with another brand new one and she runs sweet as again ...

My question is , does it sound like a coil pack on the way out ? BEING ON THE BONES OF MY ARSE lately so I can't afford to pay a mech workshop endless hours of probing.

Thanks for any input
Brad

[Halo_2]

Sounds like your dumping heaps of fuel or oil in number 4 cylinder (post pics btw)

[51 New West]

Black and wet, or sooty? Coil is easy to check, swap it to another cylinder and see if the same plug fouls, or the fouling follows the coil

[SITH]

the plug is black and wet .... most times ... tonight its black dry powdery ...I will try and gets some pics of the plugs tomorrow in the light

[thro]

Need 3 things: fuel, air, spark.

If it smells like fuel, it's not fuel.

Which leaves air and spark. New plug = should spark unless the coil is fucked?

Maybe put new plugs in, and swap the coil pack with another cylinder (if it has coil per cylinder) and see if the problem moves?



If it's not spark..... maybe something more serious.

[Rich...]

WHaloS...

You may have a dirty injector...

14 year old bike with only 32,000km, means it has spent time just sitting...

A good way to gum up injectors...

[SITH]

Ok thanks so much for all input !!
The injector idea ... I only run 98 fuel and have chucked the NULON injector cleaner in every third tank ...
The coil idea .. I will investigate this Friday as its my only day off until after new year

[thro]

Ok thanks so much for all input !!
The injector idea ... I only run 98 fuel and have chucked the NULON injector cleaner in every third tank ...
The coil idea .. I will investigate this Friday as its my only day off until after new year

If the injectors are gummed up, injector cleaner won't do shit.

On a bike that old with that few kays i'd be pulling them out and getting them ultrasonically cleaned.

[filbert]

Only running 98 fuel may be part of the problem

I only run 98 these days if 95 isn't available or I know I'll empty the tank the same day, leaving that shit sit tends to cause problems with my bikes

[SITH]

Thro ,
can you recommend anyone in our area ?
thanks in advance
Brad

[66]

move the coil first mate.
free to try.

[thro]

I got injectors cleaned on my old cage a while back, i forget who I used unfortunately.

And yeah, what [MENTION=14762]96[/MENTION] said. Do the free stuff first.

[Loud]

Do a compression test - sounds like number 4 might be low. When was the last time you checked the valve clearances?

[agrid]

Put me down for rings on number four.

[BusaSteve]

Coil, cable or cap.