PitPro 125 stalls if throttle opened quickly

[gonetopilbara]

Hi all,

at the risk of being shot down in flames for asking a question that may have been asked already (Yes I did search Google and the forums)

I have a PitPro 125 fitted with the standard Mikuni Carb.

It has been stripped down and cleaned.

It is running rich (evidence of black plug)

It would appear to have an idle screw on the side and an air screw underneath that no matter how I try I cannot get to with the bike running making it impossible to adjust accurately with the engine running.

The bike starts easily and after warming up idles fine.

When the throttle is twisted slowly the bike will rev fine without any issues up to full revs.

If you give the throttle a quick blip it stalls :confused-smiley-014

I am making an assumption that this is to do with the needle position and that I should move the clip up on the needle, thus dropping it down and allowing less fuel, but I do not know if I am wasting my time doing this or if this is even the problem without being able to adjust the air-screw while the bike is running.

The air screw is set at 2 turns out from being bottomed out.

Any help would be much appreciated as well as knowing if there is a tool that allows access to this air-screw whilst the bike is running. I am guessing not and the easiest fix would be to get one with an air-screw on the side.

Any help would be very much appreciated.

 

[sean01]

yep try the needle height adjustment mate, and make sure your air cleaner is clean and not over oiled.

also set your valve clearances as my guess is these havent been done yet..

and make sure your exhaust is sealing good in the head..

 

[gonetopilbara]

I have set both valve clearances to .003 as they have not been touches since the bikes were purchased 2 years ago (not much riding time though)

I just read the exhaust should be .004

Would this make all the difference?

I am assuming (the mother of all you know what ups) that the air screw set 2 full turns out from bottom is ok and not a biggie?

 

[sean01]

3 on the exhaust is ok but i would re set it..

air screw at 2 turns should be fine

 

[gonetopilbara]

moved the need up 2 (was on bottom).

Still same issue.

Will try higher (2 more notches left on needle)

Nothing else it could be that you can think of?

 

[sean01]

could be just the way it is after, all it is a low compression 125cc engine

 

[gonetopilbara]

Hi all,

I have moved the clip on the needle up and this has actually componded the problem further.

I have made a recording of it.

The best way I could describe the noise is it sounds like it either drowning or sucking air, but can't see anywhere it could be.

The audio is stored at this link Record009.amr - download now for free. File sharing. Software file sharing. Free file hosting. File upload. FileFactory.com
if you wish to listen to it.

If the plus is black it is obviously too rich.

By running the engine when the clip has been moved up and the bike is running leaner I would assume that this black would be burnt off the plug and it would either appear brown or white.

Bit confused on this one

 

[gonetopilbara]

#15 pilot and 95 main jet if that helps???

It used to run fine

 

[sean01]

have you replaced the spark plug? maybe its been washed with too much fuel..

have you checked the compression? worn rings don't help this situation!!

poor or bad spark is another problem you could be faced with!!

 

[trezza]

My Atomik 125 is still ****ed, it's been doing the exact same thing as yours gonetopilbara for about 3 months.

I just did the valve clearances as well, .003" intake .004" exhaust, my bike won't even idle, it only goes for about 5 seconds then stalls with that sucking sound. While it IS running if I so much as TOUCH the throttle as slowly as I can it stalls. I've been trying this with the air filter off. my spark plug is pretty black so it is rich, I've replaced the spark plug about 3 times and it doesn't help. Piece of **** is ****ed I think I'll just throw it in the tip. what a waste of $500.

Last time I rode it I could hear it shooting fuel back out the carb every few seconds with that "TSST" sound, that time I had to start the engine quickly , put it into gear and roll down a hill to force the engine to keep running. I couldn't stop or it would stall again probably, had to ride flat stick too or it was shyte.

Strange thing is when I first got it the carb was set up exactly the same as it is now and it ran fine, as soon as I first did the valve clearances it got good compression but I started having these problems.

 

[sean01]

My Atomik 125 is still ****ed, it's been doing the exact same thing as yours gonetopilbara for about 3 months.

I just did the valve clearances as well, .003" intake .004" exhaust, my bike won't even idle, it only goes for about 5 seconds then stalls with that sucking sound. While it IS running if I so much as TOUCH the throttle as slowly as I can it stalls. I've been trying this with the air filter off. my spark plug is pretty black so it is rich, I've replaced the spark plug about 3 times and it doesn't help. Piece of **** is ****ed I think I'll just throw it in the tip. what a waste of $500.

Last time I rode it I could hear it shooting fuel back out the carb every few seconds with that "TSST" sound, that time I had to start the engine quickly , put it into gear and roll down a hill to force the engine to keep running. I couldn't stop or it would stall again probably, had to ride flat stick too or it was shyte.

Strange thing is when I first got it the carb was set up exactly the same as it is now and it ran fine, as soon as I first did the valve clearances it got good compression but I started having these problems.

what have you tried to fix your problem?

sounds to me that the carb mat not be the problem, id be trying another cdi,coil or even stator plate and if you have access to one try a different carb (one that is known to run perfect)

 

[trezza]

what have you tried to fix your problem?

sounds to me that the carb mat not be the problem, id be trying another cdi,coil or even stator plate and if you have access to one try a different carb (one that is known to run perfect)

Thanks man I've made another post in the thread I made about my bike so I'll go from there.

 

[pitbike97]

hi all.

iv got a 125cc ducar engine starts first kick every time runs good BUT when its been running for about 15 mins flat out its starts to stop going full throttle, and when i try it feels like its got to much fuel in carb something like that its hard to explain but help would be very appreciated

 

[timeeh]

Trezza, try get the bike idleing (or at least running) and spray around your inlet manifold (WD40 or from what iv'e been told even water), sounds to me like it's not sealing somewhere. If thats the case you'll notice the revs change while spraying, may just need a change of seals or tightening...

 

[sean01]

hi all.

iv got a 125cc ducar engine starts first kick every time runs good BUT when its been running for about 15 mins flat out its starts to stop going full throttle, and when i try it feels like its got to much fuel in carb something like that its hard to explain but help would be very appreciated

does that read wat i think it does..

your holding it full noise for 15 minutes, poor little engine wouldnt be able to handle that lol... more than likely overheating

 

[LimZilla]

sorry to dig up an old thread but i am having the same issues with my 125cc atomik bike.

i can get the bike to idle fine and ride fine but soon as you blip the throttle to WOT it dies, but doesnt stall unless you continue to hold WOT.

i have tried swapping parts from an identical bike that runs with no issues including carby, coil, cdi, spark plug, new fuel lines, air filter and fuel filter. checked timing and adjusted valves, compression is good and no obvious intake leaks.

i have 3 bikes the same and this is the only one i cant get right.

its doing my head in... PLEASE HELP!

 

[zwebx]

needle setting..

 

[my67xr]

welcome to Miniriders LimZilla

don't forget to drop by and say G'day in the Introduce Yourself thread too


does your bike have a china Mikuni copy 22/26mm carb ?
i would recommend fitting a bigger pilot jet to it if it does, a #20 seems to be perfect for the 125's, they are only $5
http://www.dhz.com.au/buy/mikuni-carburetor-slow-main-jets/CARB-012-MIKUNI


will the bike rev if you slowly turn the throttle ?
it sounds like the Pilot jet circuit is blocked to me,
when you blip the throttle it will hesitate, and even stall


here are a couple of things to try out,
pull the fuel bowl off, remove the smaller Pilot jet, and check the hole through the centre is open/clear,
and also the holes across the sides below the threaded section, poke some wire through it.
once you are happy it's clean,
check the hole where it screws into in the base of the carby.
get a torch and shine it into the Pilot jet hole, right down the bottom you will see a tiny hole, you need to be able to see light through into the bore of the carby
again, poke a piece of wire through, something like a strand of wire off a wire brush etc.




sometimes if you take the air filter off the carby, and hold the palm of your hand over the air filter side of it to block it off.
then while your hand is there, kick the bike over a couple of times
it will create a big vacuum inside the carby, and can help clear blocked ports.
it will draw a bit of fuel up into the bore of the carby, this is ok.
refit the filter, then try kicking the bike over again and starting it up, then see if it revs ok

if after trying this, it starts revving better when blipping the throttle, then give the carby a strip down, remove both jets, idle mixture screw, choke, needle and seat and spray it all thoroughly with carby cleaner, then blow it out with compressed air, including all the ports of the carby.
when you are done, reassemble it, and try it out.


let us know how you go anyway.

cheers, craig