Buddy 125 missing at full throttle

[mjw]

Looking for some assistance with troubleshooting:

Ran fuel down almost to empty (began spluttering under throttle)
Refilled tank with normal fuel from normal servo
Lost engine response under full throttle (splutters and catches intermittently)
Eventually cut out completely and stalled
Left for several hours, came back to it and it started again
Ginger application of throttle seemed fine until under full load
Begins spluttering and missing again
Half throttle remains okay - only appears to miss under full

Checked spark - seems okay - and given that it idles and turns over fine, assume that its okay
My assumption is that by running the fuel down low, I have sucked whatever gunk that may have been in the tank through the fuel system, and I now have a partially clogged fuel line.

Does this make sense? Insuffient fuel getting to the engine under full load, but sufficient fuel under non stressed throttle?

What is the best way to get at the fuel lines and clean them?

Any help appreciated.

Matt

[Tocsik]

Ran fuel down almost to empty (began spluttering under throttle)
Refilled tank with normal fuel from normal servo
Lost engine response under full throttle (splutters and catches intermittently)
Eventually cut out completely and stalled

My assumption is that by running the fuel down low, I have sucked whatever gunk that may have been in the tank through the fuel system, and I now have a partially clogged filter of partially clogged fuel line.

Does this make sense? Insuffient fuel getting to the engine under full load, but sufficient fuel under non stressed throttle?
Matt

The fuel filter is pretty easy to access but I'm not too sure about cleaning it. They're cheap to replace, though. Access is by removing the 10mm bolts inside the underseat storage and lifting out the seat bucket.
You might try just running a good dose of Seafoam through it. Might just do the trick.
Another quick thing to try is to go ahead and replace the spark plug. You never know; it may just be misfiring at higher revs and a new one could be a cure.

[easy]

bad spark plug cap will do that i'm thinking this is a gunked up fuel filter but if that dont get it I'd replace the cap with a nkg or ngk always getting that name wrong

[Robbie]

You indicate that you refuelled because it was sputtering at full throttle.
After fueling, you indicate it still sputters at full throttle.

Although the pickup is at the bottom of the fuel tank, there is about 1/8" of distance between the bottom of the pickup and the floor of the tank.....meaning, you have to have a rather deep accumulation of debris for it to actually go down the pickup.
I consider this somewhat unlikely.

Before going too deep, look at the condition of the air filter.
Because of the air inlet position, with exception to the 2t Stella, scooters in general muck up the filter at low mileage......also, paper filters such as these are subject to swelling the media and becoming less porous if they pick up moisture.

If the filter is restricted in any way, the machine will go full rich at WOT or high speed.(sputtering/drowning in excessive fuel).....this due to the high air flow requirement at high speed.

Once satisfied that airflow restriction is not a problem, then start looking at the various ignition issues, starting at the plug.

Good luck and please share your findings.

Rob

[mjw]

Cleaned the fuel filter, checked the air filter, and replaced the spark.....
And we are all good!.

Thanks MB forum.

Matt

[skully93]

Great!

This is why I love this community.

[Howardr]

I'm betting it was the spark plug cap all along.

Howard

[PIStaker]

Matt,
Everything you did seems logical, and isn't bad to do from time to time.
But if it happened right after furling up, then I would have guessed vapor lock before anything else.
Did anyone bring that up?
...i didn't read too carefully.
Anyway, if you top off again and it happens again, pull over. Remove the gas cap, put back on and get on your way.

It's the most common issue I've seen on this board.
Mike