NC 24 cold start problem

[DanieS]

So this is where I stand.
The bike doesn’t want to start in the morning but if I try again later like say 10am the bike starts without any trouble.
Carbs are balanced, New plugs and if I get it to start in the morning the revs claim instantly if the choke is on.
I smell fuel if I try to start it in the morning so decided to keep the fuel tap closed during night and idle most of the fuel out so there is no chance of flooding but still no + results.
Does the choke have a separate jet or is it just a butterfly that cuts the air inlet.
If so I will close the air filter box with something so it doesn’t suck air and if that works I know the choke doesn’t close properly.
What is that black stuff in the carbs that opens up as the revs pick up.
If you take out the air filter you can see them.

[fastdruid]

They are CV (Constant Velocity) carbs, the black thing is the piston.

Below the pistons are the throttle valves, they are directly connected to the throttle. As you open the throttle these open reducing pressure on the engine side of the pistons, as the engine side is 'connected' to above the pistons the lowered pressure causes them to rise. This keeps airflow and fueling more constant[1].

The piston is sprung, you should be able to easily lift it by a finger (if you can reach) or something that won't damage them (or drop bits) if you can't, each one should lift and fall without sticking.

The choke should really be called an enrichment device as nothing above a moped these days actually uses a choke!
It operates by a pulling out a plunger in the side of each carb, this opens a new pathway for air to flow through the carb picking up more fuel as it does so.

Very good idea to keep the tap closed, I've had a combination of leaky tap and leaky float valves fill a sump with petrol before, engine lasted 9 miles (after fresh oil) before a big end bearing gave up, I doubt it was a coincidence!

Druid

[1] Old bikes pre-CV carbs you had to match throttle position to rpm, if you tried to whack it open it would just go bleaagh.

[DanieS]

O ok so should I clean theses air ways?
I checked on the carbs and if I open the choke then all 4 “plungers”
Pull out.
So the choke is working then???
I don’t know what can cause this cold start problem. It really F@*k’s whit my head.

Yesterday when I pushed the start button the starter didn’t want to turn the motor.
You can hear the solenoid engaging but it just made a clack sound almost as if it hits agenst something so I put the bike in 2nd and pushed it so the motor turns over and try the starter again and it was fine??????

[fastdruid]

O ok so should I clean theses air ways?
I checked on the carbs and if I open the choke then all 4 “plungers”
Pull out.
So the choke is working then???
I don’t know what can cause this cold start problem. It really F@*k’s whit my head.

If all 4 plungers are moving then the physical side of the choke is working but the inside may still be gummed up.

Druid

[DanieS]

So i can just rins the inside whit fuel?

[Neosophist]

So i can just rins the inside whit fuel?

Rinse it out with a solvent yes, fresh petrol, carb cleaner, kerosene (white gas / parafin) take your pick. then blow through holes with compressed air.

Sometimes these plungers can stick open causing fail, make sure they all go back.

If solenoid is clicking battery is discharched.

[DanieS]

The bike starts in the mornings all of a sudden and i didn't do anything??
Can be because it's not as cold any more in the evenings.
I notesed that there is no filter from the tank to the carbs and the motorcycle gerages said that i don't need one, so what stops the dirt from entering the carb's?

[Neosophist]

there is a filter inside of the tank itself!



Mine had a little rust in it! To get it out remove the petrol tap, it is held on by two 12mm bolts.

[DanieS]

Mine doesn't have a filter like that.......
That is probebly a bad thing it wount be long then my carb is blocked again.
There is a pipe that comes out the carbs just under the airbox tray at the back.
It's not conected to something but if i put my finger over it the bike dies?
Where does this pipe conect to?

[CMSMJ1]

Yesterday when I pushed the start button the starter didn’t want to turn the motor.
You can hear the solenoid engaging but it just made a clack sound almost as if it hits agenst something so I put the bike in 2nd and pushed it so the motor turns over and try the starter again and it was fine??????

So it made more than a click of the solenoid? I had an issue like this and it would engage the starter spin a touch and stop dead with a clack. I had to rock the bike in gear to turn it over and get the starter motor to spin again.

I never found the cause...but it was cured when I swapped carbs. It could be that your carbs are dribbling into the cylinders and when you try to start you get hydraulic lock which stops the motor dead. rocking it in gear allows the fuel to escape the cylinder by opening the valves. This kind of issue causes engine failures so worth checking that you have no fuel in your oil and that your carbs are working properly!!

It might be doom mongering but go tot be worth checking in case it gets serious!

Sort your fuel tap, clean and reset floats to the right height and you are good.
The pipe coming out of the back of the carbs might well be a breather?? any pics?