What is the tubes on a 4 stroke carb used for ?

nam70

New Member
Oct 13, 2017
3
0
1
72
I'm an old jet engine mech but never worked on these . Gotta learn as my grandson needs his bike..Are these tubes sensing ports and just hang down, open ?
 

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
5,845
107
63
SoCal Baby!!!
www.facebook.com
I'm an old jet engine mech but never worked on these . Gotta learn as my grandson needs his bike..Are these tubes sensing ports and just hang down, open ?
One is probably the drain tube from the float bowl and the other is an overflow tube.
If you are an old guy the carb is just a basic butterfly utility engine carb. Nothing exotic.

I assume you have a new kit out of the box.
How old is your grandson and what is he using the bike for?

Sensing port for what? :) Yes as drain tubes they would hang down open.
 

nam70

New Member
Oct 13, 2017
3
0
1
72
In jet engines, sometimes referencing signals are built in to fuel controls..Yes, the tubes are from the bowl and overflow.. Got everything in the kit. The engine will not idle. I'll look at the tank for trash.. I guess I'm relying on clean parts ,being new.. False assumption..Thanks so much for your reply..
 

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
5,845
107
63
SoCal Baby!!!
www.facebook.com
The engine will not idle. I'll look at the tank for trash.. I guess I'm relying on clean parts.
More info from you. We are not psychic.
A pic of the left side of carb.
How long have you run the motor?
Did it ever run right?

Do you have the choke in the correct position?
Those carbs have small jets.
Captured under the black idle screw is a black plastic block that is the idle jet.
Also some carbs come with a brass plug blocking the air fuel adjusting screw that needs to be removed by drilling it out.

Which kit do you have?
What gearbox is on the motor?
Where did you buy it from?
 

nam70

New Member
Oct 13, 2017
3
0
1
72
Sarcasm gets you nowhere.."I didnt imply you were psychic. Motor is new.Never idled as should..There is a small screw at the base of the forward flange,buried into hole. Also, a brass plug nearby.