bike wants to stall

[028NVD]

hi guys, just a quick question. my lifan 140 wants to stall just asi crack the throttle open, but if i opem it slowly and get past just open them it comes good an revs fine, its all warmed up but sounds like itcjust sucking air an wants to stall if i open thrortle quickly, what can i do to fix it? thanx guys

 

[sean01]

number 1 thing to do is check your valve clearances.

then id be looking at tuning the carby properly, sounds like a needle setting issue or both pilot and needle..

 

[thump*140]

028NVD what sort of engine/carb combination are you running, and what is the jetting combo you have?
Anyone who tells you cant tune the "crack throttle bog" out of a mini hasnt ridden anything in my shed...
Let us know mate, we'll give you a better jetting baseline.

 

[028NVD]

as to jetting i have no idea its a stock bse 140 bike so i have no idea what carb jetting andhow to tune. dont even know how to take carby apart to find jetting

 

[thump*140]

ok you will have a "genuine 30mm race Mikuni", known around these parts as a "Fakuni 26mm"....
They are shite, and should be replaced immediately... ha ha ha!!!
best thing to do with em, is remove them from the bike, immerse them in petrol, take 3 steps backwards, giggle, then throw a match at it. giggle some more.... pretty simple....

Failing that, you will need to start tinkering... this particular carby has a tendency to exhibit the symptoms you've described... sometime for a reason, sometimes they just up and shit themselves, with no fix available... just basically the carby failing...
You will need a #20 pilot jet, the needle clip on the middle setting, and a #92 or #95 mainjet......
there really is little choice but to whip the tools out and start tinkering mate.. carbies, particularly mini bike carbies arent rocket science in their construction... there are roughly 15 moving or removable parts to a fakuni carby, so grabs a phillips head, start pulling down, and you will see how they work pretty quick, it's a great way to learn....
As for the actual problem with your bike, it's just poor or inaccurate jetting... and is easily fixed with the right jetting combination...

 

[028NVD]

ok so where do i get jets from?

 

[sean01]

Mikuni Carburetor Slow & Main Jets Kit - DHZ Mini Moto

 

[fiffty _boytim]

did u wash your bike recently with out covering your carbie ? is your choke stuck open ? is your manifold sealing properly first things i would check b4 pulling evary thing apart

 

[028NVD]

its the 1st decent ride the bikes had since new, havent washed it, choke is all ok, **** knows about the manifold lol

 

[028NVD]

update time! so after a bit more riding today it seems to have come good in a way and my riding style seems to avoid the bog i was first experiencing. however i will be looking at upgrading my carby in a month or 2