Engine decelerates with throttle down?

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stuckonreplay

New Member
Aug 14, 2012
74
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0
Frederick, Maryland
When I pull my throttle all the way down, it goes full speed then decelerates a little then back up, then decelerates again, then back up again and again and again, what could be the cause of this? Bad oil to gas mix or accidentally drifting my foot back to activate coaster the brake?
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
Probably need to check your jetting. Sounds like it could be running too rich. What's the spark plug look like?
 

shwnrttr

Member
Dec 2, 2009
336
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38
titusville, florida
i dont think that it would be the spark. sounds like jetting to me. i had to use a smaller size jet than stock. you could try a different clip setting on the needle.
 

shwnrttr

Member
Dec 2, 2009
336
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titusville, florida
first thing you wanna do is pull spark plug out see if its black or dark in color or if its white or light in color. a dark plug its running too rich,if its white its running to lean. you want your plug to be light brown or chocolate.

try a adjusting the needle clip lower if its rich or if its lean adjust it higher
 

timboellner

Member
Apr 1, 2009
435
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16
Towson Maryland
I've seen a new guy riding around the neighborhood and thought it could be you but Frederick is a heck of a long way from Towson. I thought I could give you some help if that guy was you.
 

dragray

New Member
Mar 10, 2012
278
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Indiana
first, moving the clip on the needle will do absolutly nothing at w.o.t.
moving the clip (to lower or raise the needle) is only effective from idle to about 3/4 throttle.
after 3/4 throttle, the needle is out of the jet orifice and no longer meters the fuel.
from 3/4 throttle up, the main jet is the only thing that meters the fuel.

normally a bog like what you are describing is caused by the air-fuel ratio being too lean.
this would require a richer main jet.
normally if a carb is too rich, the engine will 4 stroke, not bog or almost quit running.

BUT, it sounds like maybe your float needs to be adjusted.
it sounds like your float bowl may be running out of fuel too soon, and then it gets just enough back in it to make the engine take off again.
too little fuel in the bowl will make it decellerate and as soon as a little miore fuel flows into the bowl it will accelerate, and it will do this over and over.
 

nightcruiser

New Member
Mar 25, 2011
1,180
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USA
I think the cord can be pushed down more
If you have the stock plug wire and boot you need to make sure that the cap is removed from your spark plug. The tip of the plug where your plug wire is attached has a cap on it, it unscrews and comes off. When it is removed you will see just a threaded stud there. You want to put the plug boot onto the threaded stud with the cap removed, otherwise it will not seat down and make a proper connection....