Engine running at half throttle,whats up????

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fall_down_stand_up

fall_down_stand_up

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Apr 26, 2009
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granbury
When I pull the clutch in and rev it up it seems to rev up slower than normal and does not rev up all the way....It acts like it is only getting half throttle....I took the slide out on the carb and when I twist the throttle the slide goes all the way to the top so I know that is not the problem....Could it be weak CDI or magneto?Could it be the spark gap?The engine runs smooth as silk and at full throttle it tools along at 21 mph....Even when I go down hills it only gets upto 24mph becouse the engine is not getting full throttle for some reason....Any help would be appreciated....
John-John
 
BarelyAWake

BarelyAWake

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Jul 21, 2009
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erm... the dreaded leaks perhaps? Carb/manifold would be likely...

That's what I would start lookin' for anyway :) Do you have idle problems?
 
fall_down_stand_up

fall_down_stand_up

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granbury
BarelyAWake said:
erm... the dreaded leaks perhaps? Carb/manifold would be likely...

That's what I would start lookin' for anyway :) Do you have idle problems?
Click to expand...
It idles perfect and runs smoothly,the spark plug is running rich and I cant choke it at all or it will die so I dought it is a air leak....The engine has 80 miles on it and im running 50:1 synthetic blend 2 stroke oil....I changed the carb out with a new one I had laying around and still the same problem....It is not 4 stroking,the idle does not go up and down it just runs smooth but wont rev up all the way....
John-John
 
george_n_texas

george_n_texas

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Sep 4, 2009
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Mine does close to the same thing...then I start peddling real hard for about 30 yards and it kicks in...I think mine is a weak magneto or wiring.
 
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bandito

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Fall down there is a thread going on with nearly the same symptoms and it was the linkage in the carb not working properly. Bikeguyjoe I think was the author and found the cure. I could be wrong but its a maybe. These 2 strokers have carbs Im not familiar with like japanese carbs from the threads I read.
 
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bandito

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I tried finding it and it would take me days, I just read it in the last 2 days I know. The problem was with the cable housing not fitting properly into the housing on the carb or somthing and it wasnt letting the linkage move full travel in the carb.......maybe?
 
BarelyAWake

BarelyAWake

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Yeah bandito I remember that - it was excessive free play in the throttle cable and using the adjuster on the top ot the carb to compensate...

Couldn't be that easy could it?
 
fall_down_stand_up

fall_down_stand_up

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granbury
Thanks for the responses....I took the slide out of the carb when I first had the problem and when I twist the throttle it goes all the way to the top....I Will take an extra throttle cable I have laying around and try it and see it it changes....If that doesnt work I will change the carb to a third one and see it that helps....
John-John
 
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bandito

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May 22, 2009
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Restriction in the flow of fuel is my guess, in the carb or tank or fuel line. Cant be a timing issue and from the symptoms I wouldnt think its electrical. If the gas cap isnt venting properly?
 
fall_down_stand_up

fall_down_stand_up

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granbury
bandito said:
Restriction in the flow of fuel is my guess, in the carb or tank or fuel line. Cant be a timing issue and from the symptoms I wouldnt think its electrical. If the gas cap isnt venting properly?
Click to expand...
I put my own little set up on the tank with a super flow shut off valve(did away with the factory junk valve),I drilled a pencil led size hole in my gas cap before I every started the motor for the first time(venting good)....I was thinking gas flow problems as well,but when I pull the fuel line loose from the carb the flow of fuel coming out is excellent....Im stumped....
John-John
 
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Sydneysider

Sydneysider

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Mar 20, 2009
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From experience I can say a blocked exhaust will most likely cause that half throttle issue, judging by the built up carbon on the plug. If it was a lighter tan or whitish color, then the thing to look for would be air leaks..
 
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