New Carburettor problems on an Aerox

I have changed the standard carburettor on my Aerox, for a new PHBG 21mm, (link below) but there is something wrong,

The mixture is to rich when the mixture is at factory settings, at 1 ½ turns out, and when I turn the mixture screw all the way in it doesn't make any difference to the revs,

I have changed the standard pilot jet from 45 to 38 but this makes no difference either,

The engine starts first time, every time, and the choke is always in throughout all of the procedures,

Do you know what the problem is.


http://www.psntuning.co.uk/scooter_parts.php?prt_id=3254

 

What´s your main jet? What air box are you using ?

 

Main Jet is 90





idle jet was 45 changed to 38

standard air box with the periscope removed

 

sounds about right to me. What colour is your plug?

 

oily and black

 

I.d go down to 85 main jet - if that doesn't work - then I would divert my attention to the starter or the floats and the level in the bowl. or get a Del orto.

 

The new jets arrived today, I put the smallest one in from the pack which is a 70 but it has not change anything,

as I said above...The mixture is to rich when the mixture is at factory settings, at 1 ½ turns out, and when I turn the mixture screw all the way in it doesn't make any difference to the revs,

The engine starts first time, every time, and the choke is always in throughout all of the procedures,


I think it should have done something,

 

What else have you done to your motor, cos a 21mm is way too big for a 50.

 

Well I don't know about 21 being way too big - but I'd be willing to bet that the level of fuel in the float bowl is too high - if the manual choke is indeed stopping the fuel getting in that way.

You should be around 100 or more main jet with a 21 and no snorkel.

Check the choke - and then bend the tab on the floats about half a mm so that it closes the needle valve sooner relative to the level in the bowl. Then try it again - but with a bigger jet - You're going to be waaaaaay poor once the fuel level in the bowl is at the right level.

Good luck -

 

70 kit
malossi multivar variator
ported sito exhaust
no snorkel.
fuel float level in the bowl is at the standard 16mm

 

the float level in the bowl has been changed now to 18mm, closing the needle valve sooner,

nothing has changed

turning the mixture screw out 4 complete turns from closed only changers the rpm by about 20 revs

 

unless... the only other thing that would do it would be an ignition problem. coil on the way out or duff spark plug......

 

What slow jet is in the carb ?

 

I have changed the standard pilot jet from 45 to 38

I changed the standard main jet from 90 to a 70

the spark plug is new, last week

 

the only thing I know that makes a wet plug other than a very rich carb is a dodgy ignition. Can you try another coil?

 

when I put the old carb back on, it runs fine,

the odd thing is that the jet in the old carb is bigger than the jet in the new carb

 

If I were you I'd leave the old one on and sell that Motoforce thing. A YSN 17.5 can be had for less than a Del Orto - and I'm impressed. Otherwise - Del Orto 17.5 -

 

one thing I did notice on one occasion last night,

after I changed the float setting I started the engine and then it cut out, and petrol started squirting out of the side vent elbows,

is this a clue to the problem

or is the carb just too big?

 

That indicates to me that you went the wrong way with the tab on the floats and the needle valve was opened more, not closed more. The bowl fills up too fast and then overflows.
Try going the other way with the tab.

 

Just to be clear on what you call "the tab" on the float,

is it the cut out two sided prong, in the middle, or the upright bit to the right,

if it is the two sided prong in the middle, would you want to see a bigger or smaller gap between "it", and the main metal body