2007 125 Atomik

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not sure on the main jet but the slow jet is a #15 I do have a #20 for it that I'm going to put back in i took it out to see if the std jet made it run better but there's not difference
 
a lot of them run a #95 main jet, a few 125's i've worked on needed a #100, and even a little bigger.
all depends on what is done to them etc, how good their ignition is, new spark plugs, leads, cdi, bigger pipes etc etc


the Pilot jet is basically for starting/idleing, and for throttle response
if you blip rev the china Mikuni 22/26mm carbys with a #15 Pilot jet, it will usually hesitate a bit then pick up, and sometimes they will even backfire too.
going up to a #20 Pilot jet should get rid of this hesitation/backfire/stutter



try starting the bike up and let it idle, get some wd40/degreaser/carby cleaner etc and spray all the joins in the carby/fuel bowl, carby/spacer, manifold/head
if the idle changes in any way then there is a vacuum leak

is the air filter fitted to the carby when it's running/tuning etc ?
and is the rubber boot sealing the throttle cable off to the carby top cap ?
 
use the adjusting mixture method i posted in post #3
then take the bike for a ride and see how it performs.
take note of where the throttle position is and what it is doing, etc if it is playing up at higher rpms.
it will help work out what is needed to sort the engine/carby tune.


even give it a bit of a run up to wot in 3rd or 4th for 5 or so seconds.
then stop/kill the engine,pull in the clutch, slow the bike down and stop, then pull the plug out to check it's colour
this will help tell you if the Main Jet needs to be changed for something bigger/smaller,
or whether you can get away with just adjusting the needle clip notch setting.
 
it might even be worth checking the valve clearances too, being a used bike
they need to be done every now and then to keep it running smooth
as they wear the gaps get smaller, and can cuse it to become hard to start, and also loose a bit of compression.

set them to .003" on the inlet, and .004" on the exhaust
here is a video link that helps explain it

[video=youtube;QJciyJRJh8Q]http://www.youtube.com/watch?v=QJciyJRJh8Q[/video]
 
Ive worked out whats going on with it:b_grind::banana:
my problem is its flooding its self the main jet is to big which is a #95 I swaped the jet out of my sons bike which is a #89 and it made it heaps better but while going through the gears but in 4th on top revs it still broke up but no where near as bad so I'm going to get a #85 main jet for it and see how that go's
 
jimbo jones said:
Ive worked out whats going on with it:b_grind::banana:
my problem is its flooding its self the main jet is to big which is a #95 I swaped the jet out of my sons bike which is a #89 and it made it heaps better but while going through the gears but in 4th on top revs it still broke up but no where near as bad so I'm going to get a #85 main jet for it and see how that go's
Click to expand...

I would be going the other way if that worked. Not down from an 89 if it's leaning out in 4th. Would be looking at a #92 main or around there. Might be best to try a few to get the optimal setting.
 
one thing you could try,
is get a thin piece of wire off an old wire brush and bend the end over at 90 degrees. trim it back so it is a couple of mm's long.
now slide the long thin end through the middle of the jet and bend the other end over and trim it back to 2mm or 3mm long
this will make it about 5 or so jet sizes smaller

then refit the jet and try it out again


but i can't say that i have ever seen a 125 that needed anything that small though ?
 
I went to my local honda dealer and got the #85 main jet I put it in and took it for a ride wow what difference it made its so smooth now right trough the rev range
 
When you reved it before with the #95 jet in it and no air filter the fuel would come out the mouth of the carby that's how bad it was fueling up
 
you shouldn't run them with no filter, it causes them to run way too rich.
you need a lightly oiled decent brand foam filter fitted to the carby to be able to tune it.

you will probably need to go back and refit the #95 Main jet when you get a decent filter back on it.
 
it wasnt running with no filter for long I took it of when I was trying to figure out the problem with it
 
yeah, i dn't mean dirt etc getting in.
the air filters need to restrict the airflow a little,
otherwise the amount of air entering the carby is a lot more than normal.
with all the extra air going in, it pressurises the fuel bowl more, and forces more fuel out through the jets.
making it seem like the engine is running rich.

so how does the spark plug look after belting along at wot in 3rd or 4th with the #85 Main jet?
 
my67xr said:
yeah, i dn't mean dirt etc getting in.
the air filters need to restrict the airflow a little,
otherwise the amount of air entering the carby is a lot more than normal.
with all the extra air going in, it pressurises the fuel bowl more, and forces more fuel out through the jets.
making it seem like the engine is running rich.

so how does the spark plug look after belting along at wot in 3rd or 4th with the #85 Main jet?
Click to expand...

yeah I understand what you ment I only took the filter of momentarily wasnt of the whole time I was trying to tune it.
And I didnt take the plug out to check it I was just happy it was running great lol jut Ill have a look at it next time I take it out
 
jimbo jones said:
When you reved it before with the #95 jet in it and no air filter the fuel would come out the mouth of the carby that's how bad it was fueling up
Click to expand...

so have you adjusted the valves?
fuel spitting back out the carby can be a sign that the inlet isn't closing properly too.
 
yeah but with the caby from you son's bike it didnt do it it was fine
 
its all sorted now any way the bike go's fine with the new jetting
 
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