spark plug

[TakinItEasy]

i dont have a manual for my 400ex, so could u guys tell me any good spark plug choices and the specs on them? thanks

[EXracer83]

Autolite 4164, not a high performance just a cross reference from stock plug.

[Sleeper]

the stock plug is a NGK DPR8Z or DENSO X24GPR-U
for extended high speed riding NGK DPR9Z or DENSO X27GPR-U

So if your getting pinging go for the DPR9Z but first make sure your running premium fuel like your supposed to.


Sleeper

[Sleeper]

Oh ya plug gap is .024 to .028 inches or .6 to .7 mm



Sleeper

[TakinItEasy]

Originally posted by Sleeper
the stock plug is a NGK DPR8Z or DENSO X24GPR-U
for extended high speed riding NGK DPR9Z or DENSO X27GPR-U

So if your getting pinging go for the DPR9Z but first make sure your running premium fuel like your supposed to.


Sleeper

u mean i gotta run like an 89 or 93 octane? ive been runnin regular 87 in it. wow i feel like a dumbass. wuts the stock compression on these things?

[kfxriderirv]

u need to run 93 in them thats wat the manual call 4 and thanx for this it really helped me get my jetting straight thanxx

[Sleeper]

Most super or premium that I have seen in oregon is 92 octane. thats what I run with the hotter plug and I don't seem to have many pinging problems. Only on take off when I've just been winding it out in 1st & 2nd for a while on a very short track.
trail riding I never have an issue.


Sleeper

[daredevilearth]

Got a 2 pack at Advanced Auto for like 4 or 5 bucks they are the substitute for the Denso and the NGK but they still work great.