Tohatsu 3.5 4 stroke Carb parts

[bluerm166]

Can anybody please identify the small black rubber 'bung' sited next to the main jet inside the carburettor.It is not on the exploded diagrams or listed.
I am wondering it is a kind of limiter ? When removed there is a narrow hole visible.
Thanks in advance.

 

[steve66]

Its a blanking plug for the pilot jet

 

[bluerm166]

Thanks Steve but why does the pilot jet need a blanking plug ? The pilot jet comes in from the side. ?

 

[steve66]

Thanks Steve but why does the pilot jet need a blanking plug ? The pilot jet comes in from the side. ?

Its the way the carb is manufactured. The pilot jets draws up from the main jet, through the pilot jet and transition ports and into the venturi. The screw on tbe side alters the amount of air fed into the slow running system. The venturi causes air pressure changes which draws a very small amount of fuel/air mixture trough the slow running circuit. The bung needs to be in place and air tight to keep the suction pressure constant.If you remove it it wont be able to draw fuel and not tick over

 

[bluerm166]

Many thanks - i have a glimmer.Thats perhaps why the main jet has side perforations ? But at any rate - the plug is a normal feature.

 

[steve66]

The emulsion tube is a totally different system. The small holes are to help fuel atomize, so a more efficient combustion can be achieved.
The easiest way to explain is imagine the carb is really 2 separate carburettors, the slow running circuit is a very simple carburettor only working when the throttle is closed. When you open the throttle the main circuit comes into play. A very small amount of fuel still comes through the slow running circuit but the majority of fuel mixture is delivered through the main jet and emulsion tube

 

[bluerm166]

Many thanks for your help.