Lifan 150 carby settings...

[Morfettminirider]

I recently took ownership of a Lifan 150cc Thumpstar. When I got it started it ran like a wet hairy dog.
After the carb was cleaned it cleared itself and I managed to maintain a consistent idle.
But....
Engine will NOT run with choke wide open. Just stops.
So with choke left on, and you go for a ride, 1st gear is very short as the engine coughs and splutters. quick shift into 2nd and off it goes, no coughing at all. When you back off the gas there is some back firing.
Because I'm new to this, I don't where to get a diagram of the carb, so I know what is what, nor do I know which is the air/fuel mix or what the recommended adjustment should be to get best acceleration and top speed.

All help appreciated.....

 

[my67xr]

how old is the bike ?
yeah it won't like running with the choke on, normally i just use the choke for a cold start, run it for a little under a minute then switch it off.
you might need to keep the revs up a touch, but it wont take long to warm up.

most carbys should run with the mixture screw turned out 1.5-2 full turns from closed (screwed all the way in)
this is a good base line setting to get the bike running and be able to tune it to suit your bike.


do you know what carby is on it now ?

does it look like this one? if it does, it's a china copy Mikuni 22/26mm

it could have this one on it ? a china Mikuni copy 30mm

 

[Morfettminirider]

Thanks buddy.
I screwed the air mix in all the way, then out 2 3/4 turns. Got it back on, I got 1st gear back yaaaa.
The choke situation is bike will start with choke on (can't see excelerator needle). As soon as I move the lever to choke off (can see excelerator needle) the engine stops.

 

[Morfettminirider]

Oh yeh mine is a Jing KE PZ27 carb with the choke lever same as Mikuni 30mm

 

[Rikchick]

I have a lifan 140 that was running a jing ke carb, jing crap..... Tossed mine and got a mikuni copy, just couldn't get mine to idle at all, I had to keep the throttle on all the time, tried to get some smaller jets for it and couldn't find any that matched....

I'm no master spinner spanner but my67xr will be able to help you out hopefully.

 

[my67xr]

Thanks buddy.
I screwed the air mix in all the way, then out 2 3/4 turns. Got it back on, I got 1st gear back yaaaa.
The choke situation is bike will start with choke on (can't see excelerator needle). As soon as I move the lever to choke off (can see excelerator needle) the engine stops.

does it have a butterfly choke? a flap inside the air filter end ?

sounds like the Pilot jet is blocked up still
take the smaller jet out ( the one in between the centre main jet and the intake manifold side of the carb)
and check that the hole through the centre of the jet is open, and all the tiny ones that go across it too if there are any
then check where the jet screws into in the base of the carby.
you should be able to see light through into the main bore of the carby
poke the holes through with a strand or 2 of copper wire to check

once that is done, then blow the carby out well.

 

[Morfettminirider]

When I took the carb apart I do remember there being 2 jets (one in front of the other). The longer one of the 2 had a hole down the length of it, with several tiny holes across it. The smaller one of the 2 had some sort of bearing in it, that moved up and down very slightly. I could not suck or blow through it.

Rikchick, was the air/fuel mix on the lifan at the front of the carb? Mine is on the bottom front of the bowl. Not enough room to get my sausage fingers in the space to adjust jet, without burning myself on the cylinder head.

 

[my67xr]

so the carby is like this one below?
if it is, then yes that's the brass Idle Mixture Screw at the front bottom

this is a rebuild kit for it

on the far left is the Idle Mixture Screw,
then the one to the right is the Pilot jet.
the mixture screw controls how much fuel can flow into the engine when it is idling and up to 1/4 throttle
the Pilot Jet, if it is blocked or part blocked will make the engine stumble when you accelerate off idle, or blip the throttle.

the 3rd small brass jet from the left is the Main Jet, it supply's fuel for pretty much anything over 1/4 throttle
the 4th one from the left is the idle speed screw, turning it in will raise the idle speed, turning it out lowers the idle speed.

the big screw at the top is the fuel bowl drain screw

 

[Morfettminirider]

Yes mine is the same.
What's the best option, put a kit in it. Or buy a Mikuni copy?

Still baffled about engine stopping when I open the butterfly choke.

 

[my67xr]

like i said in the post's above, with the engine stalling when you turn the choke off, that is a blocked Pilot Jet, or a blockage in the Pilot Circuit

you could try this,
turn the choke off,
take the filter off the carby, hold you hand over the carby inlet to block it, and kick the bike over a couple of times
now refit the air filter and try starting the bike.
it could take a couple of kick to fire up, but see if that helps unstick the blockage
if the throttle reacts a bit better then you will need to take the fuel bowl off and clean it like i mentioned before.

 

[Rikchick]

Rikchick, was the air/fuel mix on the lifan at the front of the carb? Mine is on the bottom front of the bowl. Not enough room to get my sausage fingers in the space to adjust jet, without burning myself on the cylinder head.

Yep exactly..... Makes tuning the carb very difficult.... A carby spinner would help

 

[Morfettminirider]

I took air filter off, put choke on and kicked it over a couple of times. Ended up with a palm load of petrol. Put air filter back on and kicked it over and kicked it over. Took air cleaner off gave it kick and off it went. Idle was much smoother. I did notice that when I snapped the throttle the choke would open on its own as the revs went up. Maybe that's just how the carb works.
A leaky fuel line at the filter has destroyed the glue on the foam air filter, so this needs replacing. What's best filter a K&N style filter or foam?

 

[Rikchick]

I got a uni filter for mine, best money I ever spent

 

[my67xr]

you should have had the choke off, not on, when you put your hand over it to block it.

so by choking off the carby by putting your hand over it, it has cleared some of the blockage
so the Pilot jet or pilot circuit was blocked up.

did you drain the fuel bowl after getting it running and check if there was any dirt/crap in the fuel ?
the fuel bowl will need to come off now, and you need to strip the carby down and do a major clean out, otherwise more crud could loosen and it'll block it up again


Uni Filter is the go for around $25


the choke shouldn't close when it is turned off, something is wrong there.

 

[Morfettminirider]

Ok just got back from shed.
Still got palm of gas with choke open. Shut choke, then when bike did start it did idle smoother again. To the point where from idle, I could manually fully open choke for 4 seconds before engine started to cut out. Quickly shut choke and engine would go back to idle.
Tomorrow I will strip carb down for a clean.

 

[my67xr]

yeah you only need to do it once to see if it helps.
if it does help, then you need to clean the carby out.

it will wet your hand with fuel each time you do it, yeah.

 

[Morfettminirider]

SUCCESS.....

Took 2 hours to clean carb today. Cleaned everything at least 3 times.
Main jet was so blocked I couldn't get a strand from a wire brush through it. Got plenty of daylight through it now.

Starts with choke open, idles nice a crisp, snap it open in 1st and it tears the lawn up.

Cheers for your help....

 

[Rikchick]

Awesome! Those jets are a bastard

 

[my67xr]

Good work, some of those carbys are a bit hit or miss.
Some never run right.

 

[Morfettminirider]

Now I just have to find some where around Fremantle that sells uni filter...