choke/carb help please

[MxNewb]

Hi

Can someone please confirm if the choke positions are correct ?

also the fuel/mixture screw and idle adjustment screw

pics below

the spark plug on the bike gets really black sooty from what i've read it's running too rich? too much fuel ?

pitbike is wpb 125cc race, carburettor is Jing ke Pz26 - 5k

Thanks for helping

[Mississippi Bullfrog]

On my phone so can't see the photos too clearly, but on most chokes the butterfly is closed for cold starts and is fully open when warm. When the butterfly flap is closed it restricts the airflow to enrich the mixture.

[SlowBusa]

HI,

plug tells us the mixture is about right

Edited June 24, 2018 by SlowBusa

[TimR]

choke flap should be open for riding once warm

closed for starting

[fastbob]

I agree , the exact opposite to what's written on the photos, closed for starting, open for running. That's why its called a choke . The other captions are correct. Too much fuel ? Maybe its not enough air . If you put too much oil on a foam filter it can restrict air flow and act like a second choke . So if you have been running it on choke that may explain the black plugs . I wouldn't bother with choke on a day like this .

[MxNewb]

HI,

plug tells us the mixture is about right

 

i will get more pics of the spark plug it gets darker sooty colour when riding the bike

[MxNewb]

the bike won't start with the choke closed but will start fine with choke open but when the bike has warmed up if i close choke engine will stutter then shutdown unless i give it continuous small amount of throttle to keep it idle/running with choke off

is it bad for to start the bike with choke fully open ? rather than choke closed for start up ?

Thanks all for helping

[Mississippi Bullfrog]

the bike won't start with the choke closed but will start fine with choke open but when the bike has warmed up if i close choke engine will stutter then shutdown unless i give it continuous small amount of throttle to keep it idle/running with choke off

is it bad for to start the bike with choke fully open ? rather than choke closed for start up ?

Thanks all for helping

 

In warm weather you often don't need the choke to start bike engines. If you close the choke then it's running too rich to fire up in warm weather, so just fire it up with the choke open.

I don't understand why you want to close the choke once the engine is warm - that will cause it to run too rich which is why it won't idle. Once an engine is warm you leave the choke fully open.

The problem is I'm not sure you're referring to open and closed the right way round in the first place - hence the query about the captions on the photos. Open - means that the choke flap is fully open so airflow is not restricted. Closed - means the flap sits across the airflow so restricting it. Less air mean the air-fuel mix is made richer for cold starts.

[fastbob]

the bike won't start with the choke closed but will start fine with choke open but when the bike has warmed up if i close choke engine will stutter then shutdown unless i give it continuous small amount of throttle to keep it idle/running with choke off

is it bad for to start the bike with choke fully open ? rather than choke closed for start up ?

Thanks all for helping

 

In warm weather you often don't need the choke to start bike engines. If you close the choke then it's running too rich to fire up in warm weather, so just fire it up with the choke open.

I don't understand why you want to close the choke once the engine is warm - that will cause it to run too rich which is why it won't idle. Once an engine is warm you leave the choke fully open.

The problem is I'm not sure you're referring to open and closed the right way round in the first place - hence the query about the captions on the photos. Open - means that the choke flap is fully open so airflow is not restricted. Closed - means the flap sits across the airflow so restricting it. Less air mean the air-fuel mix is made richer for cold starts.

 

Extremely well put sir , saved me the trouble . I thought my bike was knackered once and turned back after only 5 miles of what was supposed to be a day out . I'd only gone and left the choke half on hadn't I .

[MxNewb]

the bike won't start with the choke closed but will start fine with choke open but when the bike has warmed up if i close choke engine will stutter then shutdown unless i give it continuous small amount of throttle to keep it idle/running with choke off

is it bad for to start the bike with choke fully open ? rather than choke closed for start up ?

Thanks all for helping

 

In warm weather you often don't need the choke to start bike engines. If you close the choke then it's running too rich to fire up in warm weather, so just fire it up with the choke open.

I don't understand why you want to close the choke once the engine is warm - that will cause it to run too rich which is why it won't idle. Once an engine is warm you leave the choke fully open.

The problem is I'm not sure you're referring to open and closed the right way round in the first place - hence the query about the captions on the photos. Open - means that the choke flap is fully open so airflow is not restricted. Closed - means the flap sits across the airflow so restricting it. Less air mean the air-fuel mix is made richer for cold starts.

 

yes i was confused about the choke open/closed positions and now i understand it all makes sense haha what a newb i am, Thank you so much for helping

[MxNewb]

I've uploaded images of the spark plug after riding i think it's too rich ?

[Guest]

HI,

plug tells us the mixture is about right

'spose it is... for an oil tanker burning crude..??????? Black is Black......I want my light brown nose baby back....

[Mississippi Bullfrog]

The plug ought to look a light grey/brown colour. That does look like it's running too rich. Check it is the right plug for the engine as well - they vary in heat ranges. If you adjust the carb settings then two golden rules. First is to mark the original settings so you can go back to them if necessary. Second is to adjust by very small degrees - don't go winding mixtures screws by several turns - usually a quarter turn at a time is about right. Err on the side of slightly rich if you have to, burning too lean does more harm than slightly rich.

[MxNewb]

The plug ought to look a light grey/brown colour. That does look like it's running too rich. Check it is the right plug for the engine as well - they vary in heat ranges. If you adjust the carb settings then two golden rules. First is to mark the original settings so you can go back to them if necessary. Second is to adjust by very small degrees - don't go winding mixtures screws by several turns - usually a quarter turn at a time is about right. Err on the side of slightly rich if you have to, burning too lean does more harm than slightly rich.

 

the spark plug came installed new, air/fuel mixture screw is the one to adjust if its running rich?