2003 rm85 air /fuel screw

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rmrider45

Member
Sep 8, 2008
171
0
2003 rm85 air /fuel screw

this weekend i tried to adjust the air mixture screw on my sons bike .when i turned the screw it didnt seem to change anything. the bike ran fine that night and then the next morning the plug fouled out and had oil on it. ran the bike all day with a new pluig and seemed fine.?is the bike running to rich?and how can i set that screw perfect. is there a special way of doing this..thx
 
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jesse_54

Member
Apr 1, 2008
76
0
If you are fouling plugs that often it is going to take more than just adjusting the air screw. You will have to change your jet sizes.

I believe rule of thumb is if you are more than 3 turns out on the air screw you are going to have to re-jet.
 
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rmrider45

Member
Sep 8, 2008
171
0
jesse_54 said:
If you are fouling plugs that often it is going to take more than just adjusting the air screw. You will have to change your jet sizes.

I believe rule of thumb is if you are more than 3 turns out on the air screw you are going to have to re-jet.
Click to expand...


thx i only fouled one plug all summer long .and before i bought the bike it was rejetted. ii messed with the screw and made it foul the plug
?is how do i adjust that screw. turn it all the way in and then one turn out? thx
 
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00KX250Byrd

Member
Dec 15, 2007
27
0
Warm-up bike. Increase idle speed. Adjust air screw to the point where idle speed is at its highest. Adjust idle back down.

Britton
 
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jesse_54

Member
Apr 1, 2008
76
0
Yeah turn it all the way in and start turning it out.

Remember, these are FULL turns, so don't mistake a half turn as a full rotation.

As far as adjusting the air screw relative to the idle screw, I believe that's just to achieve the best idle.
 
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rmrider45

Member
Sep 8, 2008
171
0
thats another thing with this bike i can adjust the idle screw and it will idle perfect then at the end of the day it wont idle for long. it seems this bike you need to keep giving it gas alot of the time at standstill as where my 125 will idle perfect .
 
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jesse_54

Member
Apr 1, 2008
76
0

I have experienced the same problem with my 125. Start of the day it idles awesome, but when the bike is good and hot it doesn't idle worth a crap. It doesn't affect the bikes performance but it's just annoying.

I have actually found my bike to run better in cooler weather. It will idle.It actually works well for me, since living in Canada the colder temps are easily half of our riding season.
 
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rmrider45

Member
Sep 8, 2008
171
0
put a new plug in and the bike ran real good and when we would stop he would be able to kick it over with 1 or 2 kicks. today i try to start the bike and it wouldnt run . i pulled out the plug and it had oil on it and wasnt even able to be cleaned . poped a new plug in and bike seems to idle ok.(i turned the air/mixture screw in all the way and one turn out.i notice that in the front of the motor where the pipe goes in time to time i see oil driping on the ground.
what could be wrong? is it not burning the gas up fast enough
or could this have something to do with the packing in the muffler.it seems after a long day of riding the bike works fine then the next day when i try to start the bike the plug is dead .bike has ran fine all summer long till now thx on any info on this.
 
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jesse_54

Member
Apr 1, 2008
76
0
OK, if the bike ran good before you messed with the air screw this shouldn't be too hard to fix.

Did you by any chance change your fuel/oil ratio?

I would also suggest going more than 1 turn out on the air screw. Go at least 2 out.

Do you have any idea how far out the screw was before you adjusted it for the first time?

Is your air filter dirty? How hard are you running the bike? If your just chuggin' around that could foul plugs.

Last but not least, what kind of plugs are you using? Is it the same type you had in your bike when it was running smoothly?
 
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rmrider45

Member
Sep 8, 2008
171
0



same plug that was in the bike when i bought it(b9es ngk). air cleaner is clean. and my son opens up the bike all the time.and i dont remember where the air screw was at after i messed with it.?is 2 turns out more richer or is all the way in more richer
thx..
 
Last edited:
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jesse_54

Member
Apr 1, 2008
76
0
Turning the air screw OUT leans out your jetting.

Turning it IN richens your jetting.

Spanky's jetting guide has all the info you need.
 
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rmrider45

Member
Sep 8, 2008
171
0
today i turned the air /mixture screw all the way out and adjusted the throttle screw so it will idle.warm it idles perfect .but still there is oil coming from the head pipe. maybe sunday it wont rain and he can ride it and will see how it goes.if monday the bike starts after a long day of riding the problem is solved. if it dont start i am back at square one.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Back to square one indeed? Did you click the link to spankys jetting guide, that I provided for you at maxpower? I have to believe you did not, or was unable to. , http://www.maxpower-engines.com/index.php/technical-database/spankys-jetting-guide.html. If you can not use the link, say so.
 
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rmrider45

Member
Sep 8, 2008
171
0
the weather has been nice so we took the bikes out yesterday(sat nov 1)
and his bike ran great my son said .that is with the air screw almost all the way out. it still wont idle warm but he said he dont care he said it seemed like a new bike:)the bike just aint made to idle (jetting).hmm i wonder if i mess with my rm125 air screw and turn it out a little will it gain more perfomance .which would lean it out some ?
 
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