Spark plug guru's, is my jetting right?

[Ginxd00]

I just got to mess with the FCR41 carb on my 440ex, Its a 440 with mods. I did a plug chop at 1/2 and full throttle these are my findings. I want to know if I am close. Both readings came up with the same burn color. The plug is a older plug with a couple rides on it.

[roostin_dale]

looks great! I think you got it about as good as it can get!

[Ginxd00]

Originally posted by roostin_dale
looks great! I think you got it about as good as it can get!

Cool, just wanted to make sure I wasnt on the lean side.

[wilkin250r]

Definitely not lean.

[roostin_dale]

Originally posted by Ginxd00
Cool, just wanted to make sure I wasnt on the lean side.

nope, if you were lean it would be white..chalky color..

[MIKE400EX]

You should do the check with a NEW plug.

[cals400ex]

i run my leaner than that.

[roostin_dale]

never run it too lean. On a 4-stroke you want it to run a little too rich, so your on the urge of fouling a plug that its so close. Thats why at the races when the 4-strokes are riding to the gate they nail the throttle and rev it up alot, you have to keep the RPMs up so you dont foul a plug.

[blue416ex]

i run mine richer then that WAY richer its black no brown on it but it always ruins good no popping nothing like that i like it n it feels like theres a little more power but it could just be me on that

[bigbadbrad]

should i go down on my jetting if when i am on idle and i go to munch it to lift the front end up it will sometimes bog, most of the time that is but if i am rolling at a half and i snap the throotle it wont bog, should i lean it out soe, this is on a 300ex by the way

[blue416ex]

sounds like you need to lean it a bit it shouldnt bog it should be responsive and snap up that front end it sounds like you are flooding the motor with gas when you say bog that may be the problem

[DirtDevilBT]

Originally posted by MIKE400EX
You should do the check with a NEW plug.

I second that. You can go leaner than that and still be safe, but you need a new plug. The closer to the fine line the more power. I am not positive about it but I have heard from my 440 and 426 riding buddies that these ex's run better a little on the lean side. Not stupid lean, and not fake power lean. I dunno, but run the beast full throtle and check with a new plug.;)

[speedy400]

Originally posted by roostin_dale
never run it too lean. On a 4-stroke you want it to run a little too rich, so your on the urge of fouling a plug that its so close. Thats why at the races when the 4-strokes are riding to the gate they nail the throttle and rev it up alot, you have to keep the RPMs up so you dont foul a plug.
I dissagree. Thy rev them up at the gate so when they drop the clutch when the gate drops they dont bog. You do not want your plug on the verge of fouling, you want it cardboard brown IMO.-darren

[cals400ex]

leaner and mine is quicker, mainly in the upper gears. i use the upper gears a lot which many of you may not. if not, i don't sacrafice much by going larger on the mainjet a few sizes. it is a noticable difference running side by side another bike that is similar in speed to yours.

[blue416ex]

if you do run it lean watch your air temp and humidity your bike could be vulnerable to burning up because of not enough gas just be careful

[roostin_dale]

Originally posted by speedy400
I dissagree. Thy rev them up at the gate so when they drop the clutch when the gate drops they dont bog. You do not want your plug on the verge of fouling, you want it cardboard brown IMO.-darren

No, im not talking when your on the line. I mean when your riding through the pits on your way to the line...you know how four strokes jab at the throttle and rev it alot? thats beacause we run them WAY rich..trust me on this man, i know what im talking about. I have also talked ot a couple pros and local A class riders and they all say the same thing...

[speedy400]

No offence at all! but I'm just up for a good argument for $hits... why wound they want to run rich. All motors run the peppiest and best when they are lean and on the line of backfiring, or in some situations, better when they backfire a little on decel(such as high comp. pistons and full exhausts) I have learned 1/2 of my info via cals400, the jetting guru of this site, by emailing him, calling him, and pm's. Being rich just will give you a nice lag in revvin' and another layer of carbon in your combustion chamber/exhaust. Sure you might burn a little hotter, but that is what higher octane gasoline will help out on. I'd be surprised if an experianced racer wouldnt use this setup.-darren

[roostin_dale]

I do know that running it just a little bit lean...you are risking the damage of your engine..

You will get more mid-top running it rich, but a slight bog on bottom...Not sure EXACTLY why us 4-strokes do this but pros and A riders have told me this...

[cals400ex]

Originally posted by roostin_dale
I do know that running it just a little bit lean...you are risking the damage of your engine..

You will get more mid-top running it rich, but a slight bog on bottom...Not sure EXACTLY why us 4-strokes do this but pros and A riders have told me this...



i don't want to get into arguments but running them a hair leaner than richer is where you will get the gains up top (in the upper gears). i personally run my bike a bit richer on the bottom end because i can't notice a power change and with these air cooled bikes moving at slow speeds, they can get hot.

[TC426EX]

I run mine a bit rich as well... Been taught since a wee boy that a lean 4 stroke is a no-no....