Pit Pro 140

[Josh1]

Hi everyone, i bought a pit pro 140 off a mate, and its got a few problems, but the main one is the fuel mixture screw is stuck and cant be undone so its running fairly rough. It blows lots of smoke out of the exhaust and chokes when you go full throttle.
Does anyone know how to get the fuel mixture screw out and any tips on tuning it up and making it run properly again?

Thanks

 

[my67xr]

Welcome to Minirider's.

First up, get the formality's out of the way, drop in here and say hello.
http://www.miniriders.com/general-chat/20824-introduce-yourself.html


What sort of carby is on it ?
Spray some WD40 or Inox MX5 onto the mixture screw and let it sit for a couple of hour's
Depending on what carby you may need to take it off to so it

Might be worth taking the carby off anyway, remove the fuel bowl and give it a thorough clean out.
Remove the jet's and check all the hole's through the middle of the jet's are open and the hole's across the jet's too.
Blow some compressed air into the 2 or 3 hole's on the air filter side of the carby and check you can feel it coming out the hole's in the base of the carb.


Cheer's, Craig

 

[Josh1]

Hi Craig, im pretty sure its a Mikuni carb, dont have much experience with bikes, i will try what you have suggested. The problem with the mixture screw mainly is that i physically cant undo it with a screw driver as it is really small and i cant find a screw driver small enough.

Thanks

 

[my67xr]

Does the carby look like this one ?
China Mikuni 22/26mm copy

Or this, china Mikuni 28/30mm copy

Is the mixture screw under the front of the carby?




You can make up a cheap tool that make's them easy to adjust, just need a 4mm flat screwdriver bit and a short length of 5mm i/d pvc hose.
If you don't have any small bit's like that, the cheap $2 Indian shop's etc usually sell a small kit of bit's cheap
Or try the Hardware store's too.
Heat up the end of the hose with a cigarette lighter etc and slide the bit in, once it cool's it'll hold the bit tight

Once you have made the tool, sit it up inside the mixture screw tube and turn the bit so it screw's right in.
Now turn the screw back out about 1.75 full turn's
This should be close to where it need's to be

You can take the bike for a ride and try it out,
then adjust it from there if you need too, only adjust it in small increment's at a time, and let the engine run for 10-15 second's after to settle in

 

[Josh1]

Yeah, mine is the 28-30 mm carb, this is the mixture screw isnt it and what im trying to get undone?

 

[my67xr]

No you wont get that out to easily, the mixture screw is underneath at the front like my pic above.
It is made of brass and has a flat slot in it
That part you have shown is the outer part of the guide pin for the slide, the slot on the slide run's up and down on the pin that goes through the carbys' tower and stick's out inside the slide bore

Mixture screw

 

[Josh1]

Alright thanks so what should I undo or tighten on the carb to get it to idle and run better (forgot to mention it doesn't idle )

 

[my67xr]

The idle speed screw is the silver flat headed one on the centre tower, opposite side of the carby to the choke
Turn it in half a turn at a time and try running the engine to see if the idle speed is ok.
Make sure you adjust the mixture screw first before playing with the idle speed screw

 

[Josh1]

Alright thanks I'll try tinker around with them and see if it solves anything, what was the screw I was trying to adjust, what does that actually do ?

Thanks

 

[liljohn_92]

mate the screw you were trying to move isnt actually a screw. its a cap for the slide pin down the top of the carby. it keeps the slide lined up properly.

 

[my67xr]

Read the 3rd and 4th line in post #6 above, and look at the first picture

That slot down the side of the slide run's on this pin (bottom of the pic below),
which is on the inside of the carby from that part you marked on your carby

 

[Josh1]

Was told by the previous owner it was the idle screw hahahaha. I see what I can do with the idle and mixture screw and see if I can get it to run properly

 

[gottagetacheaperhobby]

And this right here is why I love miniriders. Hit a facebook page up with this question and your more than likely to get trolled hard. Right friendly bunch here at miniriders
Good luck with tuning your carb mate, now you know what your doing should be relatively easy to sort out. Its also worth checking out the jetting on your carb, the pilot jet on these mikunis seem to be to lean stock.

 

[my67xr]

If you end up cleaning out the carby, eg removing the fuel bowl then double check what jetting it has.
The Pilot jet should be a #20, and Main is a #100 on a as standard on the Mikuni copy 30mm, jetting should be fine.
Look for any dirt etc in the bottom of the fuel bowl.
And remove the 2x jet's and check that the hole's through the middle and across the jet are all open.

You should check which slot/notch the needle e clip is on too, usually they run the best on the 2nd slot from the top.
To check it, unscrew the top off the carby and pull it up to remove the slide
Once it's out compress the spring and push the end of the throttle cable out the bottom of the slide and take it out through the slot in the side of the slide.
Now pull the needle retaining clip out of the slide and the needle can come out through the top
Standard position for the needle e clip is on the 3rd notch down
Carefully push it off the needle without losing the e clip, and move it up 1 notch to the 2nd from the top.
Then refit the needle and retaining spring clip so that the v in the clip face's the slot.
Now compress the spring and refit the cable, and let the spring sit back into the top of the slide.
When refitting the slide into the carby, make sure that the long slot on the slide is facing the choke lever side of the carby, you may need to turn the slide a little to align it, when it's lined up the slide will slip down to the bottom of the carby bore and look like the pic below.
Do up the carby top and you're done.

From the air filter side of the carby you should see the top of the half moon cutout sitting around 4 mm above the bottom of the carby bore.



Main jet is the top one, pilot jet is the bottom one

This is the needle, and the e clip that set's the needle height.
Raising the e clip will lean the main jetting a touch, and lowering the e clip will richen it a touch.

If you need any help tuning it let us know, and i can run through the tuning procedure.
Make sure you clean your air filter in turp's and let it dry, then use some foam filter oil on it to stop dirt getting through into your engine, and to keep the mixture's correct.

We'll need to know what the engine is doing and at what rev's etc, and we can help you get it running sweet.

 

[Josh1]

Alright, thanks for all of your help guys, ill have a look at what i can do and let you know how i go.

 

[Josh1]

Hey guys, the bike needs a new carb, what's the best way to remove it and also the fuel tank needs draining, do you have to remove the whole tank to drain the fuel. Any tips would be appreciated thanks

 

[liljohn_92]

why does it need a new carb? it more then likely needs to be tuned to the engine properly, a new carb will probably need the same thing so wont help....

but to remove the carb you just undo the 2 bolts holding it onto the manifold and disconnect the fuel line then unscrew the top-hat and the slide pops out.

best way to drain the tank is to remove it so you can put some fresh fuel in and shake it around to get all the crap out. pretty easy to get the tank off. just gotta undo the seat(2 bolts underneath) then the 2 tank bolts.

 

[Josh1]

I've removed the carb and drained the fuel tank, the previous owner said that it does need a new carb, can someone please link me to one that would be correct for the bike?

 

[my67xr]

You could fit one of these Mikuni 22/26 carby's, will need a #20 Pilot jet to suit your 140cc engine
Mikuni | 26mm Racing Carburetor Kit | 90cc, 110cc 125cc | Buy Online Australia at DHZ

Same Mikuni 28/30 you have, jetting should be close
Mikuni | 30mm Racing Carburetor Kit | 140cc, 150cc, 160cc | Buy Online Australia at DHZ

Or fit an Oko 26mm flatslide
OKO 26mm FlateSlide Race Carby Kit ? OKO ? Buy Online Australia at DHZ
Same Oko 26mm kit ^ but with a better Uni Filter and a quick turn throttle
OKO 26MM FlatSlide Carby Kit ? OKO ? Buy Online Australia at DHZ
The oko may need rejetting to suit your engine, #37 or #38 pilot jet and a #102 or #105 main jet ($5ea at DHZ)

You will need some spray on foam air filter oil for any new air fiulter's too

 

[my67xr]

You could fit one of these Mikuni 22/26 carby's, will need a #20 Pilot jet to suit your 140cc engine
Mikuni | 26mm Racing Carburetor Kit | 90cc, 110cc 125cc | Buy Online Australia at DHZ

Same Mikuni 28/30 you have, jetting should be close
Mikuni | 30mm Racing Carburetor Kit | 140cc, 150cc, 160cc | Buy Online Australia at DHZ

Or fit an Oko 26mm flatslide
OKO 26mm FlateSlide Race Carby Kit ? OKO ? Buy Online Australia at DHZ
Same Oko 26mm kit ^ but with a better Uni Filter and a quick turn throttle
OKO 26MM FlatSlide Carby Kit ? OKO ? Buy Online Australia at DHZ
The oko may need rejetting to suit your engine, #37 or #38 pilot jet and a #102 or #105 main jet ($5ea at DHZ)

You will need some spray on foam air filter oil for any new air fiulter's too