Fuel flow problem? By porchman (Read 2,436 times)

[porchman]

my 50cc starts fine, runs good up to about 15mph, then stalls.  If i give it too much throttle, it dies.  If I keep the throttle at about 30%, it seems ok.

I've read lots of posts here and have checked:

the carb, looks clean, no leak in the diaphragm.

all the vacuum hoses seem to be ok, no leaks

fuel lines seem to be fine.

The thing's been running fine for 5 years, then the other day this started out of the blue.

Thoughts and suggestions are appreciated.

[Bashan]

Check the intake manifold for leaks. It sure sounds like a vac leak. Intake manifolds can get leaks that you can't readily see. Do you know how to check for leaks?

[Alleyoop]

Pictures of the Carb are would be good, it could be a bad LEAK maybe the INTAKE MANIFOLD has a crack in it. But where it is sputtering out is when the Needle is being lifted out. So I would check the Diapghram take it out and fold the rubber up like a bowl and pour a little gas in it and see if leaks out. Many times they may not have pin holes or rips but will leak around the plastic piece that holds them to the Cylinder.

[porchman]

bashan - i'm willing to follow any tips or guidance for how to best check for leaks

alleyoop - i saw this in another post and thought 'that's my problem!' but the diaphragm appeared ok. i will try your suggestion and report back

[jct842]

Get the engine running. Get some spray, any thing from windex, carb, cleaner, water, and I use ether engine starter. Any way while running spray all around the base of carb.

If the engine speed goes up or down you found your leak.

And you do know you do have to have the air cleaner on or your scooter will run like crap.

[porchman]

jct842 - i used windex, while it was running, sprayed all around the base of the carb and all over. the engine didn't speed up or slow down at all. it is all nice and clean now, though.

alleyoop - i did as you described and there does not appear to be a leak, not that i can tell anyway. could the needle be 'sticking' some other way? maybe i should just get a new diaphragm and see if that fixes it?

i think my 30% throttle was actually a bit high, it really only goes up to about 10-15% before it cuts out. starts easily, idles fine.

thanks for all input.

[Alleyoop]

Well take the Air tubing off and stick your finger in there and push the Slider up it should move very freely and easy and let go and it should drop down. The other thing maybe the MAIN JET is clogged did you maybe run it without a Fuel Filter. Also the Air Filter side of the carb could of clogged the AIR ports and that would not allow enough air to lift the diaphgram.
So I would take the Carb Off and Spray Carb Cleaner in all AIR HOLES on the Air Intake side of the Carb.

When you clean a Carb you Spray into every hole you see and spray should come out wherever that passage leads to.
Alleyoop

[porchman]

the diaphragm cylinder has a hole about the same diameter as the needle, adjacent to where the needle comes down and out of the cylinder. it looks to be manufactured, so i'm assuming it is supposed to be there?

[Deleted]

Jul 20, 2014 7:46:16 GMT -6 porchman said:

the diaphragm cylinder has a hole about the same diameter as the needle, adjacent to where the needle comes down and out of the cylinder. it looks to be manufactured, so i'm assuming it is supposed to be there?

yeah that's where vacuum gets in to raise the slide

[Bashan]

Alley suggested pushing the slider tube up with your finger and see if it moved easily and came back down. I would buy a whole carb rather than a rebuild kit or just a slider and diaphragm. You can get one for about 30 bucks. You might try the tile vendors at the top of the site, many of them sell parts.

[porchman]

i rechecked all over for vacuum leaks, this time w/ carb cleaner, can't find any.

i verified that the slider moves up and down easily.

i tried to remove the carb, but the screws on the choke stripped when the screwdriver got close to them, so i am stuck at the moment util i can get them out. any suggestions on the best way to do this? drill 'em out? i'll have to get them out to either further clean or replace the carb.

[Alleyoop]

You do not need to take the CHOKE off to take the carb off just follow the wires from the choke and unplug it, you know like follow the yellow brick road type of thing.

[porchman]

ah ha, thanks.
this is my first time working on the scooter, in case you couldn't tell.
i have the carb off now, am going to disassemble it, make sure the main jet isn't clogged. that's my only/best theory right now.

if i buy a new carb, does it come w/ the choke? can i just run w/out the choke, i always kick start it anyway?

[Alleyoop]

Yes they come with an ENRICHER and new hoses and either a "T" or a "Y" to connect whatever you have going there.

But I have to say I don't believe you need a new carb really, take a couple of pictures of the carb area and hoses
and don't be ashamed if the scoot is a piece of crap, we have seen all kinds of conditions people keep their scoots in
some never clean them and they actually have mud caked on their carbs and stuff. Some are rust buckets so nothing surprises us.

Some keep them so clean you can eat off of them, puts most of us to shame
Alleyoop

[Guitarman]

Rich has OCD concerning his scoots... Look at his pix when he posts them. Even the insides where dirt is supposed to collect is sparkling clean...