Bike won't idle

[hirmalde]

So I'm having a really tough time getting a ybr 125 to idle without choke. Trust me, I've done pretty much everything there is to do bar putting in a new carb altogether but still it just revs down and dies. Single carb, no diaphragm.

Idle screw is maxed out and even with full choke it can barely hold 1000rpm.

Any ideas?

Again, I have done pretty much everything or at least the things I have read up that may fix it but it still doesn't work. Looking for a detailed diagnosis path if anybody would be so kind?

I didn't realise this would get me so down but that's mechanicals for you!

Thanks in advance

[Nobby the Bastard]

Have you been fucking with the air screw? Dont you mean maxed in?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[hirmalde]

[jaffa90]

Was the pilot jet clear to see through?

[hirmalde]

[jaffa90]

You could have unwanted air going in inbetween the carb and engine.
So it`s more fuel or less air at low revs.
WD Forte on here eats YBR`s for breakfast.

[Robby]

I'll assume you're new to this and it's your first time cocking around with a carb.

First off, is the idle the only problem? Does it rev up cleanly and ride ok otherwise, or is it hesitant/lacking in power, getting worse as the bike warms up?

If so, you're probably operating the carb back to front. You're turning it off when it should be on, and vice versa.

Next up, drain the carb into a cup and look for water in the fuel. There is a drain screw on the bottom of the carb, possibly going into a narrow pipe that exits down around your right foot. There will be about half a cupful of fuel in the carb. If there is any water in there, it means you have water sitting in the bottom of your fuel tank.

Last thing if there is no water in the fuel and you were using the choke properly is to get the carb off the bike, strip and clean, and set everything up according to the workshop manual. Pay particular attention to float height and mixture screw setting.

[Jozzer]

First things first find out the standard carb settings reset them and go from there, if the carb is clean, undamaged and sealed properly (carb to head side) and it still doesn't idle then you have an issue somewhere else, fuel tap strainer, tank breather (located in the filler cap) kinked fuel line etc etc...

[hirmalde]

Thanks guys I'll check the tank breather. Definitely no water in the tank and yes it bogs down hard when revved. Refuses to rev in fact. Ordered a new carb now!

[Fizzer Thou]

Either or both of the intake manifold 'O' rings have split and so is leaking in too much air.Part #2 on the fiche

https://www.fowlersparts.co.uk/parts/5451555/ybr125ed-2005-3d91-europe-black-metallic-x/intake

By the looks of the diagram,there is a bleed tube off the side of the intake manifold.What happens if you blank that tube off with some tape or a cap?Does the engine rev properly then after resetting the carb back to the normal settings?It may well be that the hose going to that spigot has split somewhere along its length

Much cheaper than a new carb
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Just talk bikes.What else is there?

Always have a 'Plan B'

[oilyrag]

I'd start by checking the fuel level in the bowl. See if you're getting enough fuel to the bowl. Attach a clear hose to the carb drain and open the drain screw. Compare the fuel level to the spec in the manual.