Montesa 1980 349 no fuel getting through

[E19HAD]

Hi, final had time over Christmas to spend time with the Cota. Everything including carb and motor have been stripped and replaced with new parts. However, there seems to be no fuel getting through. Good spark and compression, but not the slightest glint of it starting. Any ideas?

[lemur]

So if you remove the float bowl completely and turn on the fuel tap, nothing comes out?  That would narrow the source of your problems significantly.

... is that one of the carbs where you can accidentally install the floats in backwards or upside down?

[E19HAD]

1 hour ago, lemur said:

So if you remove the float bowl completely and turn on the fuel tap, nothing comes out?  That would narrow the source of your problems significantly.

... is that one of the carbs where you can accidentally install the floats in backwards or upside down?

Hi, it's an Amal 2622 model and tbh the float could only go one way. Will give the carb a go now without the bowl attached 👍

[lemur]

That's how I test the float needle and seat operation and float height and it 100% works, if the float needle and seat is leaking or sticking or plugged you are going to see it. 

[feetupfun]

15 hours ago, E19HAD said:

Hi, final had time over Christmas to spend time with the Cota. Everything including carb and motor have been stripped and replaced with new parts. However, there seems to be no fuel getting through. Good spark and compression, but not the slightest glint of it starting. Any ideas?

More info needed. How far is the fuel getting?

[E19HAD]

4 hours ago, feetupfun said:

More info needed. How far is the fuel getting?

The float bowl fills up, but goes nowhere from there. 

[b40rt]

Is the plug wet of dry ? If dry, put a few ml down the plug hole, see what happens. 

[lemur]

After the float bowl is the main jet and emulsion tube which is the most common source of problems, that assembly can get pugged very easy.  The carburetor operates on intake vacuum pressure to draw fuel up through the emulsion tube and jets.  

[E19HAD]

1 hour ago, lemur said:

After the float bowl is the main jet and emulsion tube which is the most common source of problems, that assembly can get pugged very easy.  The carburetor operates on intake vacuum pressure to draw fuel up through the emulsion tube and jets.  

What is the best way to check and if so, clear the emulsion tube?

The Carb was totally stripped and ultrasonic cleaned before it was assembled. 

[lemur]

I inspect all the small brass parts with a stereo microscope but not everybody has one of those.  

[E19HAD]

4 minutes ago, lemur said:

I inspect all the small brass parts with a stereo microscope but not everybody has one of those.  

I've only got an old pair of Bifocal glasses 😁, but thanks for the info, will get the airline on it again. Have a great New Year. 👍 

[lineaway]

Sounds like it`s not venting. Take a pic if you can.

[E19HAD]

On 12/31/2024 at 4:23 AM, feetupfun said:

More info needed. How far is the fuel getting?

It doesn't seem to be coming out the main jet, but the float bowl is full.

[b40rt]

On 12/31/2024 at 10:15 AM, b40rt said:

Is the plug wet of dry ? If dry, put a few ml down the plug hole, see what happens. 

?????

[lemur]

6 hours ago, E19HAD said:

It doesn't seem to be coming out the main jet, but the float bowl is full.

Main jet is plugged or float bowl is not vented to atmospheric pressure or your engine is not producing sufficient vacuum to make the carb work.  Float bowl is not suppose to be full, it is suppose to maintain a level that is appropriate to the emulsion tube doing its job which is to initiate the atomization of liquid fuel into the intake path. The emulsion tube and main jet does that atomization of fuel by creating bubbles in the fuel but it can't make bubbles unless the fuel level in the float bowl is correct which is closer to half full not completely full.