140xr Pitpro Topend loosing power

[zc2000]

Hi guys,

Looking for a little help i have a Pitpro 140xr with the fake 30mm Mikuni carby i have 105 main jet and 20 pilot jet and every thing else is stock...

The bike goes well but at top speed it seems to pop and brake up

any ideas what this could be do they have a rev limiter?

any help would be great if you need more info please let me know.

 

[sean01]

sounds like you need to adjust the needle in the slide...move it 1 clip notch at a time.
if you have no joy with that maybe try dropping the main jet size down a little...

have a search for a carb thread here, its filled with carb settings from numerous riders on here.
read thru it and see what setting would best suite you for tht engine and carb

 

[thump*140]

Main Jet is too big mate.. Stock 140 with a Fakuni carby should be running a #95 main... 105 is just plain too big, and would be the cause of it breaking down at high revs...

 

[zc2000]

Ok so if i move the E clip up the needle this should help.. and if i get to the top of the needle and it no better get a smaller main...

This is the info that have on the engine... Would you class this as stock?

The engine is Genuine 1P56FMJ 140cc Lifan Big Bore Factory Race Engine
Electronic lightened flywheel with RACING ignition system
Large 27mm inlet and 23mm exhaust valve

I myself have done nothing to it...except put in the #105 main

 

[sean01]

1p56fmj(56mm piston) engine is a YX140 not a lifan(55mm piston)..will make no difference to the carb settings tho but if you ever need to order parts then its handy to know... also lifan 140 have a cast iron barrel yx have an alloy barrel..

and you say you put the 105 jet in there... what was in it before and how did it run?

and adjustment of the needle doesnt really work in that way, moving it usually adjusts the whole way the carb plays(from about 1/8 throttle thru to 3/4).
if it hesitates from like half to full then maybe both main and needle needs playing with but if its simply just from 3/4 to wide open then its just the main...

 

[zc2000]

Sean01,

Thanks for the heads up the info you supplied is great to know the more i know the better

I felt the bike lacked right from the start and seem to have trouble with its being to lean..
thats why i got the 105 perhaps i went to big... would this bike benifit from having a 26mm oko?

after i pulled the carby off i noticed that the intake holes seems very small for the carby and that it is not even a close mach up...getting a full set would this help?

 

[DvDRip]

yea man 26mm oko will solve all your problems, and the performance gains are awsome

 

[zc2000]

Looks like i will give Ken a call and see what we can do for this bike...

 

[sean01]

yep you wont look back to a stock carby ever after using an oko26.

dvdrip, wat was your jetting for a yx140?
36 pilot and 96 main wasnt it?

 

[DvDRip]

yeh mate 36 / 96 needle one clip down, i guarantee that will be perfect on any 140

 

[zc2000]

Thanks for all your help guys,

I shall get myself an OKO26mm i will let you know if i need help with that