Problem with fuel starvation

[The Rookie]

Hi, back again, after doing over 100 trouble free miles the daughters Scoot seems to be suffering fuel starvation, will run fine for a while then suddenly loose power over a couple of hundred yards before cutting out, first few times it restarted after a lot of cranking, then last night it wouldn't - at all!

Plug comes out dry, no smell of fuel at exhaust, sucking on manifold pipe to activate the valve at tank seems to allow fuel out OK, not done much else as I was flaked after pushing it 4 miles home and not eating dinner until 9:15!

Any ideas gratefully recieved.

Yes tank is brimmed!

[Vivo]

Check the carb diaphragm...

[The Rookie]

OK thanks, was planning on getting the carb out tonight and check for fuel in the bowl, will check the diaphragm as well.

[streido]

Check the fuel filter is clean. I had issues like this before on an old car. Once it cut out and stopped crap and sedimemt in the filter would fall down and clear it again then it would restart. Once i drove a bit the filter clogged up again and it cut out again.

Also double check you didnt pinch or squeeze a fuel line somewhere when youve been working on it and that all fuel lines are tight at clamps or joins.

Also check the manifold from the carb to engine is sealed good and not been split under the clamp that holds it on causing an airleak, that makes it hard to start and it idles ereatically if you got an airleak.

Did it just stop or splutter and then stop? Like when you just run out of fuel?


Could be your choke was sticking on and flooding the engine but since you said the plug isnt smelling of fuel this doesnt sound the problem.

[The Rookie]

According to my daughter it lost power and was stuttering over a couple of hundred yards and then cut out, fuel filter is clear (did a blow through test) and no pinches in the line, when I supply a vacuum to the control valve fuel runs from the end of the supply line to the carb.

Was going to check the manifold when I have the carb off tonight.

Choke goes off (hear the revs drop) and as you say the plug would be black and stinking (it was neither, though I swapped for a new plug last night anyway!)

[streido]

Bad plug lead? Or broken lead end? Sometimes they break or come apart where the plug end screws onto the lead wire.

[The Rookie]

Plug lead felt fine, solo on the roadside I couldn't check for a spark but will do when I have help!

[streido]

Could also be a little dirt or crap in the carb or a blocked jet?

In fact it could be a lot of things really, time to get the tools back out and investigate.

[whiteknight]

had the exact same problem with my scoot, exactly the same symptoms decided to die before my CBT, if i took off the diaphram cover then put it bk on the bike would start but die as soon as you give it throttle. i changed the carb and all the stuttering and cutting out stopped. so i would say its definatly the diaphram thats causing the prob.

[The Rookie]

Well the diaphragm appears in perfect condition and correctly sealed, all jets clear, still not even a put when I spin it over, have a spark, have fuel in the float bowl, have air, wouldn't even fire with some easy start!

[blue]

check your valves.

[The Rookie]

You mean inlet and exhaust in the engine?

Cranking with carb off and hand over manifold it sucks my hand in hard, so exhaust at least must be OK, harder to check the inlet!

[streido]

No, blue meant check your valve clearances. In the top of the engine at the front under the seat, look for the valve cover.

Unless they are way off i wouldnt think it was this but its worth checking if you tried everything else.

This is a strange one  Everything seems good yet it still wont fire up 

Off to do some more head scratching, post back later if i have a brainwave 

[The Rookie]

I will check the clearances, as it only happened after a period of running (to start with) I guess it's possible they have closed up a bit and as they warm up jack open, doesn't sound 100% likely though......

[blue]

check everything battery post tight. charge the battery up. check fuse. make the 2 bolds by the carb are tight make sure the 2 rings around the carb are tight. go threw and thingten what you thing needs tighten up. just dont over tighten.