Fouling Plugs

[Arven]

Hi guys,

My Whole Motocross life i have had 2strokes.. And every bike i have had, have fouled a plug or two..

Now i have just got myself a nice new 2004 KX250. This bike STILL fouls plugs, and gets hard to start when it stalls etc... I'm thinking its the spark plugs i'm using?? I have a Big pack of Iridium plugs because i keep going through them (30bucks each!!) I'm guessing i need to go Hotter to keep it burning cleanly.

Now i'm not a racer, and mainly use the bike on the trails.. Not full tit the whole time, but not putting around under the power band the whole time either.

My question is, the numbers in the plug range, Is the higher number the hotter?? Just makeing sure.

Any other advice on what it could be??

Cheers,

[digsaw]

:Oi: :no: If NGK, the lower the number the hotter the plug.:yeah:

[T.W.R]

My question is, the numbers in the plug range, Is the higher number the hotter?? Just makeing sure.

Any other advice on what it could be??

Cheers,

the plug range number is actually the reverse lower the number the hotter the grade of plug & vise versa

if say (NGK) B-8HS is standard plug, a B-7HS is a hotter type & a B-9HS is colder type.

if your riding the bike flat-out more often go for the colder type plug & if your just fluffing about go for the hotter plug.

possibly your KX is running a bit rich ?

[digsaw]

:mega: if champion plugs, its like N3 is colder than an N4,so you see the heat range for each make of plug needs to be checked by looking in the makers listings.
Just be carefull and make sure of any changes you make from the bike makers recomendations. :sherlock:

[rogson]

Good chance you are getting too much fuel (i.e. too rich) at low speed running. You may have a leaking float valve or your low speed circuit is jetted too rich (pilot jet too big).

[Hoon]

It helps if you know someone in the trade then you can get iridium plugs for $10-$15 each.
Still I'm a tight ass and can't bear to throw out a new plug that I just put in so I clean mine and use them again. Mr Muscle oven cleaner and then a nice toasting with a gas flame does it for me. Warm the bike up then swap each plug in one by one. Start it up and give it a good reving each time.

[Motu]

Hi guys,

My question is, the numbers in the plug range, Is the higher number the hotter?? Just makeing sure.


Japanese plugs (NGK,Denso) go colder as the numbers rise....the rest of the world has the plug going hotter as the numbers rise,kinda like temps themselves.Dunno why the Japs do it that way,it seems very French....maybe they went straight off the negatives...?

[Arven]

Yeah, i had a mate that worked at Repco so i grabbed a box of 4 for about 15 bucks each... But now i wished i got some a little bit hotter..

Cheers for the advice! :)

[inlinefour]

Is this not indicative of another underlying problem?:mellow:

[Motu]

[Fowled plugs?]

No,it's common on a chook chaser....

[T.W.R]

[Fowled plugs?]

No,it's common on a chook chaser....

???? don't you mean common on 2strokes:weird: if your fouling plugs on a 4stroke you've got major probs:eyepoke:

[Motu]

And what sort of bike is Arven riding??

[Henk]

Fouling plugs on a two stroke is a sign that you are jetted too rich. Putting a hotter plug in may solve the problem if you are not too far out but it is a band aid approach that may backfire if you take it too far.
Before you start changing plugs I'd make sure it's jetted right first. Bikes are usually jetted rich from new and if it hasn't been corrected out of the box no amount of plug swapping will help.

[T.W.R]

And what sort of bike is Arven riding??

have a read its a KX 250 motu !

[digsaw]

Is this not indicative of another underlying problem?????? yes it just could be.
keep an eye on the gearbox oil level you could have a stuffed crank seal and that its slurping up on gearbox lube.:whistle: :sherlock:

[F5 Dave]

have a read its a KX 250 motu !
He knows a KX is a 2smoker. You have missed Motu’s subtle humour. 2 strokes may foul plugs, but if you ‘Fowl’ a plug then clearly some sort of farm yard shenanigans are up.


RH crank seals do have a limited life & yes when they leak they will foul plugs. On a 2004, hmm, I’d say outside chance unless it’s done a whole lot of miles.

250MX bikes are bitches for trail riding as they have too much top end to be thrashing them in the tight stuff so you use that lovely bottom end. Problem is this is a dirty area of combustion as the pipe is out of tuned rev range so efficiency is low. To make it worse factories jet the bikes safe (rich), consequently plugs get fouled.

First off the bike will be too rich if the filter isn’t cleaned. But then it is worth playing with size smaller pilotjet as a start to see if that cleans up the small throttle openings as I bet it’s a bit “burbley” there.

[Danger]

I've had 5 smokers and never fouled a plug. Do some research on the internet and learn how to jet your bike properly.:baby: