Engine cuts out on initial turn of throttle. PX 125

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parky
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Sat May 09, 2020 10:21 am

Hi

My initial thought was the above problem would be sorted by a really good carburettor clean. However the carb has now been cleaned thoroughly with carb cleaner and then a really good blow through with an air line
and the problem remains the same. If I turn the throttle quickly I can manage to avoid the engine cutting out and then the engine revs fine and pulls away with no problem. I have been advised that this might be a problem with the stator plate, can anyone advise whether this could be the culprit or could there be a simpler solution. Previous to this problem the scoot ran perfectly well with no issues. So any advice or ideas would be gratefully received. Thanks

gaz_powell
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Sat May 09, 2020 6:33 pm

First thing for me would have been clean the carb as it could be the pilot jet/route. Check this again, clean out the pilot jet with a jet cleaner. Clean the filter and check air screw position.
Check petrol flow

You never mentioned if this is at initial start up or when hot or how you are using the choke.

I wouldnt say its stator at this point.

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coaster
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Sat May 09, 2020 9:57 pm

gaz_powell wrote:
Sat May 09, 2020 6:33 pm
First thing for me would have been clean the carb as it could be the pilot jet/route. Check this again, clean out the pilot jet with a jet cleaner. Clean the filter and check air screw position.
Check petrol flow

You never mentioned if this is at initial start up or when hot or how you are using the choke.

I wouldnt say its stator at this point.
+1,, it wouldnt hurt to change the plug if you havnt already done so anyway but I think if it was an ignition issue then it would get worse under load not better

parky
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Mon May 11, 2020 10:29 am

Thanks for advice, I have cleaned the carb/jets within an inch of there life. The plug has been replaced with a new one but the problem remains. If I turn the throttle very quickly I can get past the point of the engine cutting out and then the engine runs fine and pulls away no problem. I can avoid the cutting out problem if I pull the choke out fractionally and that seems to avoid the cut out problem. At the moment I am still a bit stuck for what to try next. Ideas please.

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Shaunbond
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Mon May 11, 2020 6:59 pm

It sounds like it might be very rich low down and it's bogging until you change circuits in the carb. Hence when turning the throttle quickly it's enough to jump between them.

You might have already tried but I'd try leaning up the idle circuit, first by mixture screw then by the idle jet.

All this said, what's changed between it being ok and now?
Serial scooter rider...
VMSC Committed to Scootering for 25 years

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coaster
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Mon May 11, 2020 7:58 pm

Shaunbond wrote:
Mon May 11, 2020 6:59 pm
It sounds like it might be very rich low down and it's bogging until you change circuits in the carb. Hence when turning the throttle quickly it's enough to jump between them.

You might have already tried but I'd try leaning up the idle circuit, first by mixture screw then by the idle jet.

All this said, what's changed between it being ok and now?
Anything is worth a try but he did say it improved with the choke so doesnt sound like too rich to me. My money is on an air leak or a blockage in the carb. I had a similar problem when I replaced the PHBH fitted to my old T5 with a used standard carb bought 2nd hand. It would start on choke but would not tickover and would die if I didnt rev it. I stripped it and cleaned it to no avail and finally bought a new Spaco 24mm patern carb and it ran perfectly aftwr that.

Smudge
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Mon May 11, 2020 8:19 pm

I've had this. Cleaned carb dunno how many times without success until the last time. I used a paperclip to clean the fuelway and out pops a tiny sliver of brass. Obviously the previous owner liked really tight jets.

gaz_powell
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Mon May 11, 2020 8:58 pm

It continues to point to carb, agree about cleaning it and replacement.

I had a T5 that was doing similar, cleaned carb loads then times, new gaskets, flated carb and box, then moved onto plug, lead, cdi, stator to no avail......swapped carb to a one from a runner and bingo....bought new Spaco job done

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Shaunbond
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Mon May 11, 2020 9:08 pm

coaster wrote:
Mon May 11, 2020 7:58 pm
Shaunbond wrote:
Mon May 11, 2020 6:59 pm
It sounds like it might be very rich low down and it's bogging until you change circuits in the carb. Hence when turning the throttle quickly it's enough to jump between them.

You might have already tried but I'd try leaning up the idle circuit, first by mixture screw then by the idle jet.

All this said, what's changed between it being ok and now?
Anything is worth a try but he did say it improved with the choke so doesnt sound like too rich to me. My money is on an air leak or a blockage in the carb. I had a similar problem when I replaced the PHBH fitted to my old T5 with a used standard carb bought 2nd hand. It would start on choke but would not tickover and would die if I didnt rev it. I stripped it and cleaned it to no avail and finally bought a new Spaco 24mm patern carb and it ran perfectly aftwr that.
Missed the bit about the choke...
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VMSC Committed to Scootering for 25 years

parky
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Tue May 12, 2020 4:15 pm

Thanks for the advice chaps. I will try the various suggestions and see how I get on. If I still can't crack the problem then I suppose I might have to think about replacing the carb, however I was hoping to avoid that.

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