Mikuni Carb Mixture Setup

[gaz]

I've read the mikuni sticky before you ask and I didnt find it that helpful, so anyway

I have a 125cc Gen 2 with a 26mm Mikuni carb

It runs too rich and the mixture screw is under the carb and too close to the head to adjust it whilst its running, so

Any tips on a stock setup?

For example, screw all the way in then say 2 turns out?

(Tried that but its runs too boggy and rich again)

Thanks

[bra69ers]

there is a special screwdriver that you can get which is angled so you will get to the screw. if running rich screw in. only a bit at a time though.

[gaz]

What screwdriver is this? I have a 90º screwdriver and a small ratchet 90º screwdriver and I cant get in there for shiz. The only way I could do it, is superglue the ratchet bit into the screw and do it that way, even then its abit much because superglue isnt made to resist torque forces.

[Despise]

I know the problem, so awkward. Use a small screwdriver piece (the ones you get with drills) then use a 10" spanner on it.

crude way of doing it yes but it works

[gaz]

ok cheers for that, i'll try give that a pop in a bit, that is honestly one of the stupidest places i've seen a screw. I'll let you know how it goes

[gaz]

couldnt get to it using that method im afraid, I even tried supergluing a screw bit in there so I could adjust it later but it wouldnt stick.

So, I have set it at 1 and a half turns out, it runs alright but not how it should do, it pops and cracks a fair bit, I think this is too lean correct?

[jthump110]

too rich mate.

[gaz]

Right for anyone who's interested i've almost sorted out the mixture, I found this to be of great help

http://www.ooracing.com/tuningTips.htm

Read about jetting

For anyone who is having problems read on;

I screwed the mixture all the way in, out one and a half turns and it was setteling on a high idle and not very "snappy" meaning its lean, I screwed it out a further quarter of a turn making 1 and 3/4 turns out, this was better but still setteling on a high idle so I turned it another quarter making it 2 turns out, this was alot better, snappy and responsive and setteling on a slightly higher idle only just. Meaning this is still lean but its now down to 1/8 adjustments.

Take in mind that every adjustment ment the carb had to come off a hot engine, and then put back on again.
For anyone who's worked with these mikuni carbs and on pitbike/bikes will understand the amount of times I got burnt lol

So for a 26mm mikuni carb on a loncin 125cc engine, i'd set 2 turns out a baseline the rest is personal preferance

Cheers for the replies everyone


jthump I thought it ment it was too rich because theres too much fuel making it pop and stuff but I thought i'd only turned it out one turn or so. Thats when I thought im going to start this all over and do it properly lol

[Despise]

Originally Posted by gaz

ok cheers for that, i'll try give that a pop in a bit, that is honestly one of the stupidest places i've seen a screw. I'll let you know how it goes

indeed stupid design. The screw on my old chink carb was in a better place lol