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Yup. My p125x (1978, stock cylinder, 20/20 carb) has started spluttering to a stop when stopping at lights or a stop signs on a downhill gradient. Has no problem on the straight or on an uphill. Seems to happen with full tank, half tank, less than half tank.
Compression is 100psi, so i'm thinking there's a slight leak somewhere? (not at head or exhaust tho - they seem sound). Could the low-ish compression be part of the problem? What could be the main reason? Any experience advice hugely welcome. Scoot runs great otherwise.
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Re: 1st Post :) p125x dies at downhill stops
Oliver Tamborine wrote:
Yup. My p125x (1978, stock cylinder, 20/20 carb) has started spluttering to a stop when stopping at lights or a stop signs on a downhill gradient. Has no problem on the straight or on an uphill. Seems to happen with full tank, half tank, less than half tank.
Compression is 100psi, so i'm thinking there's a slight leak somewhere? (not at head or exhaust tho - they seem sound). Could the low-ish compression be part of the problem? What could be the main reason? Any experience advice hugely welcome. Scoot runs great otherwise.
Sounds like a fuel delivery issue. First thing I would check would be the float and needle in the carb. Needle could be getting stuck. When was the last time you cleaned and rebuilt carb? Replaced the float and needle? Next thing I would check would be fuel line and tap.
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Re: 1st Post :) p125x dies at downhill stops
it's a brand new Spaco carb.
oh i forgot... once it has died, it is difficult to kick start again. What seems to work is to kick it 2-3 times with ignition off, turn the tap to low fuel, turn ignition back on and then it starts (sometimes on first kick!).
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Re: 1st Post :) p125x dies at downhill stops
Oliver Tamborine wrote:
it's a brand new Spaco carb.
oh i forgot... once it has died, it is difficult to kick start again. What seems to work is to kick it 2-3 times with ignition off, turn the tap to low fuel, turn ignition back on and then it starts (sometimes on first kick!).
You mean turn the tap to reserve? Maybe it's your fuel tap then.
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Re: 1st Post :) p125x dies at downhill stops
brentscheffler wrote:
You mean turn the tap to reserve? Maybe it's your fuel tap then.
Yes. i'll check the fuel tap. Not been looked at in a while. Thanks.
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Curious why you replaced your carb and how the bike ran before doing so?
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If you have rust or crap in your fuel tank it could be moving forward and clogging your tap when pointing downhill. Might be worth a look in the tank.
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Willie B wrote:
Curious why you replaced your carb and how the bike ran before doing so?
Starts were difficult and pulling off could end in engine dying. The mating surface on the carb to the engine block was slightly warped. I got a new carb 'just to see' what the difference would be between a new carb and re-surfacing the warp The new carb fixed the starts. I'm now thinking the fuel tap was maybe partly at fault too.
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when it dies, are you holding in the clutch and coasting? is the hill very steep?
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Oliver Tamborine wrote:
Willie B wrote:
Curious why you replaced your carb and how the bike ran before doing so?
Starts were difficult and pulling off could end in engine dying. The mating surface on the carb to the engine block was slightly warped. I got a new carb 'just to see' what the difference would be between a new carb and re-surfacing the warp The new carb fixed the starts. I'm now thinking the fuel tap was maybe partly at fault too.
How long have you owned the scooter? Had you put a ton of miles on it before experiencing the warped base, or are you trying to sort a new to you scooter?
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TrojanMod wrote:
when it dies, are you holding in the clutch and coasting? is the hill very steep?
Does not have to be very steep. The scenario is;
Clutch in, shift to 1st and then holding clutch in and trying to keep the revs up with the throttle to prevent the engine dying, while riding the clutch a little. This works if i can go through the stop without slowing too much but if i have to stop or slow to a near stop, then the engine splutters out.
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Willie B wrote:
How long have you owned the scooter? Had you put a ton of miles on it before experiencing the warped base, or are you trying to sort a new to you scooter?
The scooter is new to me. Had it a few weeks. So... tweaking and trouble shooting to iron out the not-quite-rights. Thought i had it dialled in pretty good, untill these downhill stops started.
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I'm assuming you've checked the timing? There are tons of things that could be causing your scoot to do what it's doing, but starting with the basics and moving forward in steps will ensure you aren't chasing your tail.
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Willie B wrote:
I'm assuming you've checked the timing? There are tons of things that could be causing your scoot to do what it's doing, but starting with the basics and moving forward in steps will ensure you aren't chasing your tail.
Checked the timing. It needed a little adjustment and is now dead on. Double checked after with a strobe.
Checked ignition coil. Checked HT lead. New spark plug, correctly gapped.
Replaced base gasket. De-coked cylinder. Flattened Cylinder to Head mating surfaces (that gave a big improvement with general performance).
My focus is now on the fuel tap as i must admit i haven't touched it yet
Also planning to see what the main seals are like, i guess.
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Update!

Pulled the gas tank, drained and filtered the gas. Gas was very gritty and fue filter was clogged up with grit and a white-ish 'mush' Pulled the filter, cleaned it out, and flushed the gas tank. Scooter now runs muuuuch better on idle, with both idle and mix screws tightened up a little too. Idling on down hill stops fine. Oh yay!

Brand new fuel tap is in the post too 8)
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