New Rider
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Never stop moding.
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Joined: May 4, 2014 20:30:02 GMT -5
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Post by nathanial on Aug 20, 2014 0:55:39 GMT -5
I was riding to work going about 55 like I do everyday and then all of a sudden I lost power and started to decelerate so I let off the throttle and pushed back on it but now once I get the throttle past 1/2 way I get sputtering, backfiring, and deceleration. So I can only go about 40 with the throttle just below 1/2 without it giving me problems. Does anyone have any ideas?
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Post by carasdad on Aug 20, 2014 15:27:29 GMT -5
If this is a 150cc... I have had 3 customers have the exact same thing happen to them. We found it to be blown/worn piston rings. A compression test showed the compression way low(100-110 psi)...at which point we put a few drops of oil in the plug hole...cranked it and compression went up just under 40 psi. A quick cylinder hone and a new set of rings...they were back on the road. Allow me to explain the reason for the symptoms you have and the customers had...as many understand that blown/worn rings would just lower compression and power. If we look at how an engine operates we see that there is compression for the power..on the upstroke. HOWEVER!! What do we have on the downstroke?.. Vacuum...that is what draws the air/fuel mixture into the cylinder. Therefore the low compression from poorly sealing piston rings gives a decrease in power on the upstroke and the loss of vacuum on the downstroke creates an erratic air/fuel flow which causes your erratic running. My advice..check your compression..post it here for folks and we will go from there. 140-150psi is good...with 160-170psi being on the high side..but it is still within range and will produce a bit more power.  Glenn |
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Post by alleyoop on Aug 20, 2014 16:05:31 GMT -5
Let me ask this question: will it idle good and not die on you after a run to work or whenever?
If yes I would check your Diaphragm it may be ripped and will not hold the needle out of the main jet. When that happens you have the butterfly wide open and sucking in a lot of air and since the needle has dropped some not enough fuel. If you back off the throttle to close the butterfly some cutting off some air it settles down.
Alleyoop
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..BAD TO THE BONE..