cough & splutter high revs esp. 3rd and 4th gear. Help!!!

[motomike07]

Hey guys

I’ve been running my new bike in recently (pitpro 140xr) and it’s been running sweet as…until the motor starts to get warm/hot and begins to splutter and lose power from ½ throttle onwards. It’s especially predominant when going flat out in 3rd and 4th gear.

I’ve read through various threads and think that the main jet might need to be bigger? I’m running the stock mikuni carby (30mm I think?). Does anyone know what the standard main jet size is? Also, where can I get a bigger one and what size should I run?

Could it also be a CDI/electrical problem? Or will this be fixed by moving the e clip up one or 2 positions?

i think the bike is running a bit lean (hot engine, can't keep the high revs etc.) i havent' checked the plug yet, but i will tomorrow.

Any help would be great fellas

 

[motoXXX]

ill try help to the best of my knowledge...

the pitpro 140xr and all other china bikes come from the factory so the bikes run great out of the box so if a customer wants a test ride it will not bog etc etc out of the box so from the factory they come tuned for just the starting of the bike and so it runs good when cold for about 10 mins after the bike warms up abit the tuning is out and causes it to bog/splutter etc etc...

to solve this problem in one go and give you more performance go on ebay and spend $100 on a 26mm oko carby and a UNI filter...and maybe a couple different jet sizes so u can have i fiddle to get the best performance out of your engine...

if you want to try tune your standard carby on the bike now you will most likely need a bigger main jet and maybe a different slow jet...

these carby from china often arrive with mud/gloggy crap in the bowl of the carby and threwout the carb so id give you advise to strip it down to everylittle piece and soak it it some petrol and swish around to clean all the crap out then give everything a nice blow out with the air compressor then you may find you bike will run great THIS HAPPENS ON ALOT OF CASES WITH CHINA BIKES DONT WORRY ABOUT IT ONCE YOU GET IT SORTED IT WILL BE SWEET...

dont forget to wash and oil you air filter after every ride...

these copy mikuni carbs are VERY HARD TO TUNE becuase u cant get the the mixture screw easily as its on the bottom of the carby and the engine is in the way (you may be able to make yourself a tool out of a old screw driver etc etc) but its still a bastard of a jobb ...

with the 26mm oko carby it has a easy to get to mixture screw that u can turn with your finger at anytime...and they will also give you better performace so for 100 buks id grab one...

when your carby is tuned properly at running temperature your bike will probly run like shit for the first 10 minutes until it warms up then you should be sweet...

you should warm your bike up for 5 minutes everytime u ride so when u get it out of the shed start it up give it some revs for a minute or 2 then let it idle for a couple mins...

 

[motomike07]

cheers for that motoxxx

but if i start messing with the air/mix screw on either carby (oko or stock), wont' that mess up my revs below 3/4 throttle that is fine?

i've read that just changing the main jet size can fix this problem?

i will probably get an oko carby, but if i could fix this problem for less $$ then i'll do that.

has anyone changed the main jet size on their 140xr?

 

[motoXXX]

many of people have changed them and they are sweet but the oko gives alot better throttle responce aswell threw high and low revs and is well worth the money as you can give it a touch up tune in like 30 seconds if it start to run rough but if you are to try that on a 30mm mikuni you will be looknig at a 10-15 min jobb or MORE

 

[motomike07]

well sounds like the oko 26mm carby is the go. is that the flatside carby? also, the stock carby takes a 40mm uni filter...will this be the same size for the oko carby?

and where can i buy bigger jets if you know? pitpro?

 

[motoXXX]

im pretty sure your local bike shop would have jet MAYBE MAYBE NOT im not to sure about the uni filter someone here will no masterspoon will no what one ask him when he comes on send him a pm

and yes its the flatside carbi dont get the 28mm get the 26mm its better for a un highly modified engine

 

[motomike07]

cheers man

i'll go find out about the jets from my moto shop and wait for 'the spoon' to help us out with the filter size

legend

 

[motoXXX]

hey mate yeh no worries if you need any other help just ask

 

[cass38a]

Have a read thru these.
http://www.miniriders.com.au/forum/tech-talk/12025-95-main-jet-105-a.html
http://www.miniriders.com.au/forum/mini-chat/11232-mikuni-102-5-main-jet-2.html
http://www.miniriders.com.au/forum/tech-talk/12055-do-i-need-retune-carby-125-140cc.html

 

[motomike07]

cheers for the part numbers in the earlier threads cass

i'm going to order them tomorow at the moto shop

legend

 

[MITTZ]

my 140s runs great and i never had to tune it at all from the factory! just so you know its not ALL chinas that come set up bad!

 

[coolmodee01]

problem solved

water in carby = clean

valve clearances = do them

you will find when your engine heats up you clearances close up resaulting in bad things

a good service after about 3-4 tanks is a must

 

[motoXXX]

yes i forgot to mention vavle clearences mate

i set my lifan 140 at .003 for inlet and .005 for exhaust and a couple members said they did it to what i said and there bikes are going great so give it ago mate

if you dont no how tell me and ill get you a link for a video of how to do it

 

[bnlazy]

i went and put the 100 buckers towards a oko 26mm carb on mi pitpro 140xr works great its very sensitive and give the bike alot more power i run the mixture screw all the way to the right i ave got to change the pilot jet size as it tends to bog if i trottle to hard off the mark atm i have got a jet size of 41 in it so i will have to change that.
amywayzz hope best works out
ILL POST A PIC OF MI BIKE HOPEFULLY TOMORROW


oko 26mm = BEST

 

[Peter1230]

the exact same thing happens on my brother pitpro 125.... but we r gonna wait till it runs in... 3-4 tanks.

 

[hammer69]

Yeah same here,
I have the 110cc pit pro and it will go hard and sweet for around 20mins, then it will just bog and bog. Till I let it cool down, would a oko 26mm fit on this bike and fix the problem, also run good??
Cheers

 

[thump*140]

if you want to run a 26mm oko flatslide carby (great carby by the way) you will need a 95 or a 100 main jet... seems to be the standard proven set up with these carbies...