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white plug...paranoid??

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Posted by: njkx---------------------

Last night I re-jetted my bike for the warmer weather....1/4 turn in on the fuel screw and went from 182 main jet to 180. Bike runs 100% better at idle and off the bottom....seems about the same at full throttle...very happy with the way it runs..

I couldn't really do a proper plug check since it was 10:30 at night and the neighbors already hate me so I just rolled on the throttle in 2nd gear till I got wide open and then shut off. I checked the plug and it was basically white...not in a bad way...it just looked brand new. The plug had only had 3 rides on it prior to this. (sorry no pic).

My question is every time I've pulled a plug out it has been brown to black...never white...I find it hard to believe the bike would lean out significantly by only going down one jet size...am I just being paranoid or is it OK for a plug to look this way? Is there another way to know if I am too lean??

05 YZ250f


Posted by: bigred455---------------------

Reading a plug for jetting is pretty much useless,it takes quite some time to get color on a new plug. Example: Put a used plug in there that has time on it with color and check it.It will be the same color as before not white. Reading a plug up by the insulator to fine tune jetting will have you walking in circles. You can be 4 steps richer on your main jet, and when pulling a fairly new plug,it will be white. When I say white, I mean stock color porcelain white,not grainy shiny white.The magazine and websites explaining how to check sparkplugs for jetting are totally off . If you have a fairly new plug with a couple rides on it ,and it is still white, that is fine. Jetting without dynos etc. the best and only way is by moving the jets and needle ,listen and feel your motor,it will tell you which way it needs to go.
If you are lean on the needle, power will be very thin.You will shoot right through the power and rpms,power will be weak and thin. If you are lean on the pilot or fuel screw, you will get a bog or slight hesitation when cracking the throttle open from the closed position or idle hang up. The main jet believe it or not,this is the first time you probably heard this. It is very tough to tell when the main is lean,it will run good and strong pull hard etc. I like to go rich on the main just to see ,if I move 2 richer and it still pulls strong and all the way through,then I was lean. I will move another 2 richer, the power now feels dull,the power and rpms start to climb then it hits a wall,it sounds dull and it will have a slight skip sound to it. If you are unsure about going 2 richer to begin with, and you know it is rich already,then move 2 down on the main ,and see if the power is better.If it is better, move another 2 down,same thing, the power did not improve go back. Do not be afraid to move jets,you will not seize,you will know you are rich or lean way before seizure,ESPECIALLY ON A 4 STROKE. Use good terrain to put a load on the motor especially testing your main jet,if you are testing on flat hard land ,the rpms will climb too easily and the motor will not labor!


Posted by: bigred455---------------------

Isn't like this didn't happen before,but I just love it when you get no reply,just a simple thanks. I Make sure I do!


Posted by: scatman---------------------

Quote:
Originally Posted by bigred455
Isn't like this didn't happen before,but I just love it when you get no reply,just a simple thanks. I Make sure I do!


If it makes you feel any better...thanks. Very informative post with lots of useful information.


Posted by: bigred455---------------------

Quote:
Originally Posted by scatman
If it makes you feel any better...thanks. Very informative post with lots of useful information.


Didn't mean you,but your welcome!!!!!!!! I see a lot of subscribers giving good accurate replies to a question,but no response from the original thread starter.


Posted by: scatman---------------------

Quote:
Originally Posted by bigred455
Didn't mean you,but your welcome!!!!!!!! I see a lot of subscribers giving good accurate replies to a question,but no response from the original thread starter.


I was just trying to lighten the mood and let you know that even though the original thread poster didnt thank you, I appreciate the advice you gave.


Posted by: bigred455---------------------

Quote:
Originally Posted by scatman
I was just trying to lighten the mood and let you know that even though the original thread poster didnt thank you, I appreciate the advice you gave.


You are ALL RIGHT!


Posted by: njkx---------------------

Quote:
Originally Posted by bigred455
Isn't like this didn't happen before,but I just love it when you get no reply,just a simple thanks. I Make sure I do!



Sorry man...I haven't been able to check the site in a while...wife, 2 kids, 60 hr a week job and I like to ride once in a while too.

If you look at some of my other threads you'll see that I've thanked others in the past.

Are you posting to help or are you looking for some sort of recognition?


Posted by: bigred455---------------------

Please
I wan't the attention,ME ME ME .


Posted by: morganbike---------------------

Big Red, your post was very helpfull to us but the problem I have is that I dont ride the bike ,My son does and I can only listen to it and whatch the performance (CRF 250).On really hot days 90 degrees the bike runs poor and we have 38.5 HP on the dyno but seems to run like a standard machine on hot days.Should I change the main to smaller.? We run a 185 main and the standard is 172 ??.


Posted by: bigred455---------------------

Quote:
Originally Posted by morganbike
Big Red, your post was very helpfull to us but the problem I have is that I dont ride the bike ,My son does and I can only listen to it and whatch the performance (CRF 250).On really hot days 90 degrees the bike runs poor and we have 38.5 HP on the dyno but seems to run like a standard machine on hot days.Should I change the main to smaller.? We run a 185 main and the standard is 172 ??.


I will not tell you what jet to run,even if I had the same bike same mods etc.If you and your son think the main is rich,move it down 2, 180 main.See if it pulls stronger and throughout,if it does improve, move it another 2, 175 main and repeat,until you get no further improvments.
If the main is rich and it is noticeable,move 2 steps at a time,you will not seize.The thing is, moving 1 size at a time is a waste and sometimes hard to detect because 1 size on keihin main is so minute,especially if the rich condition is so noticeable. If you move the main down 2, to a 180, and see no improvement,look into needle position. If you do see a improvement keep going down until you get no improvement, AND GO BACK TO THE LAST MAIN. The main is easy to change on the 4 strokes,there is a lot of room between the cases and the 17mm plug.Just take the bowl plug off, and slip a 6mm socket on the main and loosen. Move those jets, do not be intimidated by seizing.



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