Author Topic: Spark plugs, why do they fail...?  (Read 2754 times)

0 Members and 1 Guest are viewing this topic.

Offline Norway

  • Jr. Member
  • **
  • Posts: 24
Spark plugs, why do they fail...?
« on: September 13, 2010, 07:03:43 AM »
Can anyone explain why spark plugs seem to just give up....?
Went riding today, all seems fine, bike starts easy as allways.
Rides for 30 min, quick stop, 5-6 min, then bike wont start....
Innvestigating, and no spark...
Replaces spark plug, all is fine again.
Less than 2 hours on this plug, NGK br 9 es.
Same thing has happend before, also on other bikes,
and in my snowmobile.

But there dont seem to be any reasonable patern,
ran my previous spark plug for a long time...


Bj?rn Ivar
Low-cost racing was the idea... Used to be...

Offline Polar-Bus

  • Hero Member
  • *****
  • Posts: 1,023
Re: Spark plugs, why do they fail...?
« Reply #1 on: September 13, 2010, 07:34:36 AM »
Can anyone explain why spark plugs seem to just give up....?
Went riding today, all seems fine, bike starts easy as allways.
Rides for 30 min, quick stop, 5-6 min, then bike wont start....
Innvestigating, and no spark...
Replaces spark plug, all is fine again.
Less than 2 hours on this plug, NGK br 9 es.
Same thing has happend before, also on other bikes,
and in my snowmobile.

But there dont seem to be any reasonable patern,
ran my previous spark plug for a long time...


Bj?rn Ivar

Usually rich air/fuel mixture oil fouling, and /or excessive low speed  driving. I have a NGK B8EG that's almost 2 years old still burns perfect. I am also jetted much leaner than stock. Race fuel also helps for a "cleaner" burn, but not necessary to eliminate plug fouling
« Last Edit: September 13, 2010, 07:49:21 AM by Polar-Bus »
01' KX500
'84 GPz1100
'87 GSX-R  750
'06 HD Fatboy
'73 Kawi H1
'03 CRG KX500 Shifter kart

Offline don46

  • Hero Member
  • *****
  • Posts: 1,140
Re: Spark plugs, why do they fail...?
« Reply #2 on: September 13, 2010, 09:17:49 AM »
You could try a br9evx they are a bit more money but seem to work better than the es series, they are the fine wire platinum electrodes. Good synthetic oil helps prevent fouling, but in the end its about the jetting more than anything else, I guess in afterthought I would also say that there could be electrical issues ie weak spark

When the 89 KX 500 came out I bought one, I couldn't get the needle I wanted at the time so I waited and everytime I rode it I fouled a plug till I got the needle, it would start idle and as soon as I went to leave it would foul out a plug. after jetting no issues
« Last Edit: September 13, 2010, 09:20:01 AM by don46 »
Live today, for tomorrow may never come

Offline oic0

  • Full Member
  • ***
  • Posts: 172
Re: Spark plugs, why do they fail...?
« Reply #3 on: September 13, 2010, 09:18:52 AM »
I usually clean mine up and pop em back in. I don't know if it's advisable or safe, but I often burn mine clean with my stove top or gas grill ;)

It also helps if you let the bike clear its throat every now and then. Just cruising around? get her into the powerband for a second every now and then.
« Last Edit: September 13, 2010, 09:23:53 AM by oic0 »
2000 KX500
1998 Warrior, with RD350 engine (Blown up)
1973 RD350 (In storage)

Offline Coyote13

  • Newbie
  • *
  • Posts: 8
Re: Spark plugs, why do they fail...?
« Reply #4 on: September 15, 2010, 06:37:05 AM »
I have had better luck with the br8, they are one step hotter than the 9s you are running. This in addition with proper jetting and you should not foul plugs. :lol:

Offline bob larry

  • Full Member
  • ***
  • Posts: 150
Re: Spark plugs, why do they fail...?
« Reply #5 on: September 15, 2010, 08:59:52 AM »
Ya toss all your ES plugs and run EG... few bucks more but way better plug
my $0.02
2001 KX500