Carby Tuning - Sorry guys

[n_dorphin]

Hey guys,

Ok, New to these pit bikes sorry.
I have a FMR 140cc Lifan bike. It was taken to shop to be tuned and serviced when after I got it second hand. Shop put a new 26mm carby on it.
They also checked valves etc.

Ran ok after shop had it, but now starting to gain confidence and skills.

It has a 20 Idle, and 100 Main jet. C Clip on bottom.

When you free rev the bike (WOT) it hesitates or stalls.
When riding and snap to (WOT) it hesitates and then revs fine.

I've tried adjusting Mixture and C-Clip - Lowest best and can not eliminate issue.

Please Help! Going away riding this weekend.

Jason

 

[n_dorphin]

I should add this arvo i had a ride around yard and it ran much better apart from High RPM.
I found choke was in middle setting - Not sure what this means??

Jas

 

[my67xr]

if the c clip is on the bottom slot of the needle, the main jet is too small
might be worth buying a #105 and #107, then start with the c clip in the middle slot on the needle.
possibly need to adjust the mixture screw a little too.

 

[n_dorphin]

Awesome thanks. I'll grab one tomorrow. Cheers Jason

 

[rotn50]

Sometimes the hesitation from idle to WOT can be a low idle adjustment, try turning the idle up a bit if this is happening, but as for the hesitation whilst riding the bike when it is at higher than idle speed you may need to try what craig has just mentioned about jets and needle adjustments. Hey dude theres no need to apologise for asking questions, there wouldnt be much to give advice on if there wasnt peeps new to this and needing advice on trying to get there ride running good.

 

[Oznewbie]

How many turns out on the mixture screw ?

Might help with diagnosis

 

[Oznewbie]

How many turns out on the mixture screw ?

Might help with diagnosis

 

[n_dorphin]

I think I have the mixture screw about 2.5 turns out.

After calling and talking to bike shop today they said to check valves. I said they had not long ago adjusted them. So anyway I just finished and they were way too tight. Now adjusted and will test out in the morning. Has STRONGER compression now tho! Guess its looking good. Thanks Jas

 

[my67xr]

with the mixture screw being 2.5 turns out, does it rev quickly/clean and crisply when you 'blip' the throttle a little?

 

[my67xr]

and is it a Mikuni carby (china copy) on it?

 

[n_dorphin]

Yep I think its a copy. It was running really bad even set at that setting. Valve now adjusted by myself so will test and report back in the morning. Thanks Guys!! You're all awesome

 

[n_dorphin]

Alright here's the update.

Running better. Valve had tightened and now double checked. Starting and running better.
Mixture I think is about 3.25 turns out.

When on idle and blip the throttle it hesitates or goes to die.
Also when riding and go to WOT it hesitates, Not as bad as before but still annoying.

Any further guides? Cheers Fellas

 

[my67xr]

i would be turning the fuel mixture screw back in till it stops, (the screw underneath the carby, intake manifold side)
then turn it out 1.5 to 2 turns and see what it does then