newbie problem when revving out 4th

[sickpitbikebro]

hey guys just been having my first few rides of my pitpro140xr. since ive been running it in, just been taking it easy. but yeh pit thru almost 2 tanks and starting to open it up now. the problem is 1st and 2nd are fine. the end of 3rd and into 4th when u are on the throttle it kinda chokes and does not rev smooth. im hoping its just a small common problem, maybe i need to tune something?

any help would be greatly appreciated. thanks very much fellas.

matt

 

[coolmodee01]

maybe lack of fuel in the higher rev range
there will be a thread mentioning the jet size for that carby somwhere
if not throw a 26mm oko carby on it and that will feed it good as

have a search see what ya can find

 

[sickpitbikebro]

hey there. thanks very much for the reply. yeh cause im new to all this i didnt know what to actually search for soz, went thru pages of stuff bit i really had no idea what the problem was. ill scope out the 'jet size' for that carbie. i think its a 30mm? cheers

 

[sickpitbikebro]

.....its just a stock bike and pretty much brand new so i didnt think i would have to change anything to rev it out in each gear. im considering taking it to a moto joint but just thought id check on here first....still searching the threads

 

[ASR Rider]

adjust the air/fuel screw all the way in and out 2 - 2.5 turns, if ur cabie says mikuni on it, it will most likely be one of these,

... here is another one the red is the idle screw..

 

[sickpitbikebro]

ASRrider your a champ thanks so much. ill take some tools and go for a ride and see if i can fix the problem.

 

[motoluver]

The air screw has nothing to do with it. Either main jet or possibly an electrical fault. My bike in the high rpms has lately been fucking up, its like the motor cuts in and out when revving it hard. I haven't tried to find the problem yet.

 

[sickpitbikebro]

hey guys just wondering whats the best tool to get at that screw. bought those right angled flat/phillips head doubled ended things but they were too big. tried using one of those smaller flathead drivers but was on a weird angle. what u guys use?

and also anyone know which turn does what. like left turn= less air and right turn= more air? or does it control both air/fuel?

sorry guys might sound silly bust really just getting into the basics.

cheers

 

[edzy]

mine used to bog out in high gears.
make sure your fuel line is only a downhill the whole way from the tap to the carb. if the line has to go uphill when your reving it hard in a high gear it wont be able to push that feul quick enough!

 

[ASR Rider]

oh and motoluver your air/fuel mix screw has everything to do with it, if its set to to lean the bike has not got enough fuel going throught the carb to the engine when its going flat nacker

 

[ASR Rider]

oh yer sickpitbikebro, if that don't work watch my vid on carbs and u'll see an e clip mov it up once and try it and if its still the same try to move it up again its pretty straight forward if u copy what i did later

ASR

 

[sickpitbikebro]

sorry to bring this up again. just 2 quick questions
1- having trouble getting at the screw any suggestions for tools?
2- which way would i turn the screw to run it richer. its just the stock carb off my pitpro140xr.

i know there should be no real probs, its pretty much a brand new bike so yeh. thanks again fellas

 

[ASR Rider]

mate the worst thing is u gotta take the carb off watch my vid it will explain every thing, and my advice would be to set the screw to 2.5 turns out from the bottom (All the way in) and use the e clip to make adjustments. Heres My Carby Vid it will explain everything i have said to do... YouTube - Carby Pull Down, Clean And Rebuild

Cheers

 

[sickpitbikebro]

ASR rider, again thanks for your help. went for a ride this arvo but just took it easy. ill watch ya clip tomorrow. cheers

 

[cass38a]

The mixture screw wont be your problem at WOT. IF the bike is running sweet from idle to half throttle then the mixture screw (the little sucker you cant get to) wont be your problem. The Eclip may have some effect but it could also be your CDI.

 

[cass38a]

I made up a special tool to get to the screw by cutting a screwdriver in half and re joininng it with a bit of flexible hydrolic tube so it can flex into the right position. But sometimes its best to just take the carb off and make small adjustments.

 

[ASR Rider]

cass it has nothing to do with low range mid range, if the bike is cutting at the top end it hasn't got enough fuel, these bikes always have that problem. by adjusting the screw u will increse fuel flow when its flat stick, man i am so tired of explaining this shit

 

[cass38a]

I am not so sure you have expliaind it. The Mikuni tunining manual clearly states that the mixture at wide open throttle is governed by the main jet. It may be starved of fuel when running flat out but adjusting the idle mixture sure wont increase the fuel flow at wide open throttle.

I would love you to explain it clear enough to make me believe that Mikuni dont know their own carbs.

 

[STICK]

Screw only governs idle to mid,then needle takes it from there

 

[ducar.r.spec]

hence why u have an idle jet and a main jet, mixture adjusts ur idle jet
e clip needs to be moved up a notch