Air mixture screw thingy... I think

smokinbenrage

New Member
May 18, 2008
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Ok, so after many weeks of not being able to ride, I finally have it up and running!!!:ride2: I have 2 questions.

#1. I was playing with the air mixture screw when my bike was idling. I noticed that if I turn it clockwise the engine starts to rev higher. If I turn it counter-clockwise, it revs lower. My question is what is the best adjustment for the screw and if I have it too tight, will it reck my engine?

#2. My engine starts to make a bbbbbbbbbbbbbbb (not smooth) noise at certain throttle positions. When I twist it some more, it sounds like, mmmmmmmmmm (smooth). What could be going on with the engine? I asked my dad and he said that it is because the engine is out of balance... is this true. If so, how do I fix it?

Thanks,

Ben
 

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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Duvall, WA PNW
www.sickbikeparts.com
#1. I was playing with the air mixture screw when my bike was idling. I noticed that if I turn it clockwise the engine starts to rev higher. If I turn it counter-clockwise, it revs lower. My question is what is the best adjustment for the screw and if I have it too tight, will it reck my engine?

#2. My engine starts to make a bbbbbbbbbbbbbbb (not smooth) noise at certain throttle positions. When I twist it some more, it sounds like, mmmmmmmmmm (smooth). What could be going on with the engine? I asked my dad and he said that it is because the engine is out of balance... is this true. If so, how do I fix it?
1) Makes sense - because that is your idle screw.
2) Allow it to break in and then start adjusting stuff per all the threads here. (Not a matter or turning screws unfortunately)
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
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up north now
Ok, so after many weeks of not being able to ride, I finally have it up and running!!!:ride2: I have 2 questions.

#1. I was playing with the air mixture screw when my bike was idling. I noticed that if I turn it clockwise the engine starts to rev higher. If I turn it counter-clockwise, it revs lower. My question is what is the best adjustment for the screw and if I have it too tight, will it reck my engine?

#2. My engine starts to make a bbbbbbbbbbbbbbb (not smooth) noise at certain throttle positions. When I twist it some more, it sounds like, mmmmmmmmmm (smooth). What could be going on with the engine? I asked my dad and he said that it is because the engine is out of balance... is this true. If so, how do I fix it?

Thanks,

Ben
1. As stated the idle screw is for SPEED ONLY, not mixture.
2. That sounds about right...without a long winded explanation, a two cycle engine (when properly set up) will run smooth (mmmmm) until it has very little load on it, then it will break into a 4 cycle...( bbbbbbbbb). When you come to a hill, or twist the throttle a little more it will again clear out and run smooth...(mmmmm).

Only when you are really reving it up will it stay "smooth" since it's got a load on it at 30+ mph.

You are fine, ride the thing!;)
 
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Skyliner70cc

Member
Mar 8, 2008
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16
Its easily mistaken for an air bleed screw. An airbleed screw would be perfect for our carbs to fine tune the los end mixture setting.