Guys I need Help! mysterious REALLY HIGH IDLE??

97BoredOutBlasta

97BoredOutBlasta

New Member
Feb 25, 2009
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Hood River, OR
Hey guys, I just got my blaster back from the Yamaha Shop, i got a new clutch put in, the clutch felt great, but after a short ride, it would idle at like half throttle! Its fine in gear riding, but when i dissengage the clutch or put it in neutral to idle, its like im giving it half throttle. I checked the obvious like the throttle cable, (no TORS) I messed with the idle adjust. screw, but nuthing. I dont know these bikes to well, i just got it like a month ago, Im stumped. Im guessing maybe the black slidetube in the carb is hung up, only when there is no load on the engine, which is why it only did it in neutral or when the clutch is dissengaged? Hit me back guys, I wanna ride haha
 
Hmm, I'm having the exact same issue. I checked all the obvious too, no airleaks, cleaned the carb, checked the slide. I'm stumped too. Hopefully someone has some insight.
 
ya man it sucks, the throttle/fuel system is pretty strait forward, or so i thought. im stumped. it sucks becuase i wanna go ride this weekend, i just got the new clutch in it, it was riding like a whole new machine. then this. I hope one of the Blaster O.G.'s will help us out, it has most likely happened to somone on this forum. Any input would help us both and would be much appritiated!
 
check the tors box under your hood. When i first took my tors off it did this and i never unhooked that box. You say you have tors removed already so you prolly already removed the box im talkng about but just trying to help.
 
you tried finding a leak w/ carb cleaner? did you spray around the exhaust too?

it could also be a very lean jetting at idle so def do as blaster99 says and check the airscrew.
 
Ya thanks guys i will try the airscrew, which one is that? whats it look like? It was really wierd, i figured i would ride a little, just stay in gear and rip around and it rode it it felt wierd, first and second felt ok, and then my midrange was practically gone in third fourth and fifth, and then when i tried to coast to a stop and hit the killswitch it wouldnt turn off! it was revving like three quarters throttle, kinda scary so i jumped off and pulled my plug wire(the first thing that came to mind idk) and it still detonated a little and then finally died! i dont know what to do the throttle cable wasnt hung up or nothin no slack in it. I think its definately carbueration, any help would be much appritiated!
 
97BoredOutBlasta said:
Ya thanks guys i will try the airscrew, which one is that? whats it look like? It was really wierd, i figured i would ride a little, just stay in gear and rip around and it rode it it felt wierd, first and second felt ok, and then my midrange was practically gone in third fourth and fifth, and then when i tried to coast to a stop and hit the killswitch it wouldnt turn off! it was revving like three quarters throttle, kinda scary so i jumped off and pulled my plug wire(the first thing that came to mind idk) and it still detonated a little and then finally died! i dont know what to do the throttle cable wasnt hung up or nothin no slack in it. I think its definately carbueration, any help would be much appritiated!
Click to expand...

its def the airscrew,its right next to the choke,its a flat head cant miss it
 
oh ok ya so i should turn that flathead brass screw in all the way, and then turn it out 1 1/2 turns? that rite? i will try that. what is the function of this air screw? sorry guys im still tryin to figure these things out.
 
ya turning the airscrew helped alot, actually, its still a little bit high, but tolerable. im gonna mess with it more, i think that if i get a new silencer so i get my backpressure back, i know 2strokes are sensitive to exhaust flow. and i put some no name mix in my gas cuz i was out of yamalube. mistake. i need to drain that out and put fresh mix in it. any pointers on carb tuning? i want to basically learn how the stock mikuni carb works. , wheres the idle adjust screw? by the way no TORS
 
well, it wouldn't be the tors anyway. all the tors does is cut off fuel flow it if thinks the carb is stuck open. pain in the ass, but it wouldn't cause hi revs.
the airscrew (on 4strokes is a pilot screw and works the oppposite way w/ fuel instead of air) is what meters the air to fuel mixture in the pilot circuit which is at idle on up. the pilot circuit is always open.
but the first thing you always check when tuning a carb is the float level. if this is too high, all your circuits will run rich or vise versa.
then tune the pilot circuit by finding what setting will give you the highest revs. then set your idle speed which is the thumbscrew between the tank and airbox under the seat.
then you set your main jet circuit by doin spark plug tests. then set the needle position last.

also, if you're still getting erratically high revs then you've def got an airleak SOMEWHERE. you would have to have a VERY lean mix to get the chamber hot enough to continue firing after you hit the killswitch. unless you let it sit idling way too long w/o putting a fan to it or somehow moving the air around the engine. are you sure you sprayed carb cleaner everywhere? at the head, spark plug, cylinder base, around the reed cage, carb intake, exhaust port.....
 
Last edited:
quam said:
well, it wouldn't be the tors anyway. all the tors does is cut off fuel flow it if thinks the carb is stuck open. pain in the ass, but it wouldn't cause hi revs.
the airscrew (on 4strokes is a pilot screw and works the oppposite way w/ fuel instead of air) is what meters the air to fuel mixture in the pilot circuit which is at idle on up. the pilot circuit is always open.
but the first thing you always check when tuning a carb is the float level. if this is too high, all your circuits will run rich or vise versa.
then tune the pilot circuit by finding what setting will give you the highest revs. then set your idle speed which is the thumbscrew between the tank and airbox under the seat.
then you set your main jet circuit by doin spark plug tests. then set the needle position last.

also, if you're still getting erratically high revs then you've def got an airleak SOMEWHERE. you would have to have a VERY lean mix to get the chamber hot enough to continue firing after you hit the killswitch. unless you let it sit idling way too long w/o putting a fan to it or somehow moving the air around the engine. are you sure you sprayed carb cleaner everywhere? at the head, spark plug, cylinder base, around the reed cage, carb intake, exhaust port.....
Click to expand...

check all your head and base gaskets,the idle screw is on top of the tors box its a flat head finger turn thing youll see it
 
I had the same prob

I got told about a float or somthing that goes down in the carb wen you de accelerate so I checked that out and there was small bits of dirt in it so it wudnt go down at all or it wud slow so I cleaned it up and it worked gr8
 
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