Jetting setup for lifan 150cc, 1P56FMJ engine?

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MasterSpoon

MasterSpoon

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ok so i have my new bike, 2007 Pitpro XR140, arrived yesterday
everything says it should have the 1P55FMJ but it has the 1P56FMJ, not fussed
it seems to run however it feels, i have only run it about 5 times today just playing and about 10-20 minutes each time, first time went great, second time noticed on initial throttle take off it would bog down then fire right up, went to start it when it had cooled down and it wouldn't rev without the choke on, pulled carbie down a bit later and checked it out as read about needle clip should be on lowest, it was, bike ran fine after reassembly (nothing changed)
so my question to those that have tuned these properly what setup are you running, my current setup is
Mikuni 30mm carbie, 100 main jet, 20 on the other, needle clip on lowest setting
dual stage stocko air filter, stocko XR140 exhaust
Engine is on quality castrol oil and running BP ultimate fuel
so thats what it comes standard with, what have you boys changed them to?
 
First ...there is no Mikuni 100# main !!...if the size in your carb is like in Keihin then it will be a tad to small and the pilot will be muuuuch to small...you need at least a 38# and the needleclip has to be always in the middle ...its easier to check this way!!
 
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i will pull the carbie apart again some time to see if i can spot if its a mikuni or keihin jet, but i'm pretty damn sure it has 100 written on the top
has anyone actually tuned one of these motors to tell me first hand how they set theres up?
 
got a copy 30mm mikuni the other day and it has a 20 pilot and 100 main i am changing the 100 main to a 105 i have spare, wont be albe to run it on the bike till i get a 30mm manifold and modify it to fit my bike
 
I know where the mountain is coming from ........ it would be great if someone could check the actual drill size of the #100 jet from a Mikuni "30" to see if they are using the Keihin jetting system (#100 = 0.0380") OR the Mikuni system (fuel flow in cc/min) where a #100 = about a #110 in Keihin sizing .

I can't check first hand since I sold both of my Mikuni "30's" . But I can verify that the carb I bought as part of a kit from DHZ had a #100 main in it and I'm pretty sure that the "30" off the DHZ "138" bike had a #97.5 main in it ..... indicating that they're using the Keihin sizes for the mains and the Mikuni sizes for the pilots ....... .
 
I don't get it? You can order genuine Mikuni jets to suit these carbs. I got a 105 in mine now???
 
MasterSpoon said:
ok so i have my new bike, 2007 Pitpro XR140, arrived yesterday
everything says it should have the 1P55FMJ but it has the 1P56FMJ, not fussed

Mikuni 30mm carbie, 100 main jet, 20 on the other, needle clip on lowest setting
Click to expand...

I think you will find that you actually have a 2008 bike thats why it has a
1P56FMJ motor.
When i got mine i was told that even though the pitpro specs say its a 30mm mikuni,it is actually a 26mm mikuni,so if your bike is standard that is more than likely a 26mm
 
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fair enough, well can one of the guys that know all about carbies inform me of a good starting point.
I gather from themountain that it should be something like a Keihin 102.5? main jet and a mikuni 38 or 40 pilot? My plan is to go down to local carbie place, so getting proper mikuni jets (aslong as they will fit) is no problem. Just wanna know what ones to get as a good start. Bike runs fairly ordinary once its warm. Also what style of jets do these take? I am led to believe there are several different styles of jets, what "style" jets are in these mikuni ripoffs?
 
120 cc with oval bore 26mm or 30mm opening

It takes the round jets that are mikuni. I have and run the same carb mentioned with a mechanical external choke ( non pull style). Not sure if it is fake or not but runs the bike all the same.
First off, the intake needs to match the 30mm opening. aka... Port the hell out of it or buy a new intake from tb.
Second, I have a big cam and High Compression piston on a 120cc zongshen motor with the big head so it breaths well at 900ft above sea level.
The 100 main and 20 pilot stock did not work at all with needle in the bottom position or on the rich needle clip.
I tried a 132.5 main (slightly rich on the main for the needle position rich ) and the 25 pilot was too lean with the needle position rich). This bogs in the main or higher RPM and too lean on the pilot or off idle.

My next attempt will be to raise the needle position to the mid clip position and try the 40 or 35pilot. This should be the right combo.

I think mikuni might build these carbs for engine companys as a B2B contract under restrictive guidlines designed for specific fitment or budget. It is a better design in my openion as the carb opening is leaner in the idle to mid range to help with torq then allowes for a greater top speed using the maximum velocity prduced by a 26mm. best of both worlds for engines 120-145cc. Above the 150cc go with a true 26mm round carb as it will supply more fuel up to the 1/2 throtle position or if you have alot of engine work to demand the extra fuel. Standard carb size for the 120-145cc are 22-24mm.

Let me know what you come up with on your settings...
 
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I have a lifan 150 with a tm flat slide and rubber manifold as well as a moto club exhaust . I have a 100 main and a 10 on the pilot jet , these motors take a 26 mm carb stock and going up in air (28mm)..means down jetting. I am a little lean on top by a little and need to order a 105 main. I have no clue why everyone's pilot jet ideas are so rich ? My carb came with a 15 in it which was rich.
 
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