New Carburettor problems on an Aerox

It's the cut out in the middle -
The one on the right limits the travel of the floats (and sometimes needs pushing more out the way so they can drop lower).

But we are interested in the middle forked tab. You need to bend it so it actions the needle valve more/quicker. If you send me a photo with it in the carb I could tell you which way - I don't know your carb and it's different to a PWK or a Del Orto.

Go easy. 0.5 of a mm has a fairly big impact -

And if you start it and it goes without drowning - be very, very careful - because suddenly the engine will be very poor with a 70 jet - once the carb has stopped overflowing & spewing petrol in the engine.

 

The picture of the float is up the right way, as it would be in the body of the carb,

so to action the needle valve and close the jet off more quickly, I will open the gap up, Yes?

 

That's correct -
Check the needle valve itself - and the seat inside the hole - there might be some grit or something stopping it closing properly when the floats come up -

 

This is a bit worrying,

I have bent the tag on the float to close the jet off more quickly,

but now the petrol comes out of the elbow vents when I turn the key to start the engine,

 

I'm about to give up,

I bought a new carb,

and then a set of idle jets, and then a set of Main jets, to cure the problems with the new carb, but it still doesn't work,

the seller really doesn't want to know, saying setting up a carb is the hardest thing in the World,

and Dellorto wont help because I didn't buy it from them,

have you ever felt that you've been stuffed.

 

It looks like you overdid the bending of the tab and the needle valve won't close now, so it's overflowing. As a rough guide, when the floats are level with the face of the carb that the float bowl butts up to, the needle valve should have closed and you can check this by blowing through the fuel line and when the floats are lifted up, the needle should close the valve and you shouldn't be able to blow through the pipe any more. it's an on/off situation and the height of the float determines when, just like the float in a toilet cistern.

If you are really stuck, you could send to me in the post; I'll set the float height for you and send it back to you.

 

can you do a pic of the carb upside down with the floats & needle valve on there?
looking at a photo of the floats again , are you sure you've put them in right side up? Is there a little hole opposite the forked tab through which to connect the needle valve to the fork tab ?

Floats usually go on with the float hanging down rather than the way you show them. If that's the case here, then the fuel level will have to be stupidly high to action the needle valve.
And the carb will overflow as you experience.

On the other hand the Del orto PHBR has the floats 'upside down' - with a tab like yours.

This is why we need a photo!

 

1. No there isn't, no hole

2. I agree, but this is the right way

 

Well there goes that hypothesis........

 

This was a very good test,

It verified that the needle works and seals, whilst blowing my brains out,

thank you for the offer,

I reset the float at 17mm,......stock book value is 16mm, now its back together I think I should have set it 1 mil under not 1 mil over

I reassembled and turned the key, but the engine wont start, there was no fuel coming out of the breather elbows, this looks like a good sign at the mo, I wondered if I may have blown some debris out of the jet,

but now the battery is flat and on charge until the morning.

 

That's because the standard carb has a 12mm venturi and the air is being sucked in at high velocity which in turn atomises the fuel well. However a 12mm carb is really a bit too small for a 70cc motor and restricts the engines breathing. Try pursing your lips together and breathing through a small gap, you have to suck hard and the air is travelling pretty fast. Now open your mouth a bit more, and breathing is easy and the air is passing your lips reasonably quick . Open your mouthfully and take take a breath air passes in very slowly. The air velocity through the venturi of a 21mm carb is probably less than half that of a 12mm and it does not atomise the fuel well.

Unless you are running a highly tuned 70cc motor a 17.5mm or 19mm carb are much easier to dial in and will give a much better throttle response.

 

Ok, I understand

 

The picture shows the bottom of the carb, with no hole in the floats metal arm for the needle jet

 

it looks like the bottom of the metal arm, does the upward pushing of the needle, Not the two prong part which seams to be there only to pull the needle back down again,

 

these 4 pictures above are with the float set at manufacturers spec, with the float at 16mm from the body when closed

 

good photos. We must assume that mr Bizzle is right ! I can see nothing wrong with any of that.
Sorry if I mucked you about. i run a PWK 21mm with an intake about the same size as your box on my all days motor with no trub- i assumed yours should work too . And yes- i did have issues with the bowl level.....

 

so what is the answer?

is the only option now to discard this carb for a smaller one.

 

the revs are all over the place,

I set the idle and it changes after I rev it up a bit,

the mixture screw works at its best, when it is screwed in all the way, but it feels like it wants to still be a bit weaker,

the plug is very wet and black.

 

if i was you I would stop mucking about and drop the engine off the frame, cap the exhaust with a plate and a piece of inner tube, then put a manometer/valve in the admission pipe and do a 1.5 bar pressure test.
A simpler version is to remove the ignition, use a schraeder valve in a cylinder of resin in the admission pipe with a collar, and pressurize the engine to 1.5 bar and then dunk the engine cylinder first (with spark plug & exhaust capped off air tight fashion) in a tank of water up to the middle of the tranny case.
Then you can see where the leak is.
Because I think that that is the root of the problem.
It sounds like a lot of aggro- but it will save time in the long run.

Good luck.

 

are you saying that there is a problem with the carb,