Tuning the carby on 125 Atomik??

[thumpster]

Can anyone tell me how to tune the carby properly. I've tried adjusting the idle and mixture screw but just cant seem to get it to stay at a constant idle. Where should i start with the mixture screw, all the way in then how many turns out? There must be a trick to it coz these carby's are pretty basic.

cheers

 

[red_demon24]

first what size carby is it its probably eather a 25 or 26mm mikuni but the more info you put up the better?
and with the air mixture screw all the way in and 2 1/2 turns out and go from there?
make sure your chokes off unless the bikes not warm of course.

 

[cass38a]

I recon you should start with your main jet. Get that right first (you need to do a plug chop at WOT to check it).

Then adjust the needle at half throttle (doing a plug chop) and you will need a marker on the handle grip so you know where half throttle is (exactly)

When both of these are right then play with the mixture screw.

I recon the best way is to start all the way in and half a turn out.

Do a test ride (at full temprature) then adjust the mixture screw by one quarter turn at a time until it runs sweet and dosent die off the line.

If you start 2.5 turns out you dont know which way to go as it could need to go in or out to get it right.

Once you have it perfect be very accurate and wind it all the way in again and count exactly how many turns it is so you can always re set it if you need to take it out to clean it etc.

All of this needs to be done at full operating temprature otherwise you waste your time.

 

[sickpitbikebro]

good post here thats what i was after as well. on my pitpro140 (mikuni30mm (26mm) or whatever that screw is a fair mission to get to especially if its running hot. what u guys using to turn the screw?

 

[cass38a]

I made a special tool by cutting a screw driver and rejoining it with a bit of hydrolic hose. It could flex around the engine and into the bottom of the carby.

The ideal way to adjust the screw is to wind you idle screw in until the engine is reving at about 1700rpm. Then using the flexable screwdriver wind the mixture screw in until the bike stats to run shit then wind it back out until it runs shit. Count the number of turns between these to crappy positions and set it mid way between the two points. (then do the trick to find out where it sits from all the way in so yo can get there again).

Doing it this way burns the crap out of your fingers. You can buy a special moto screwdriver that is designed to get to that screw (the snap on dealer in Dubbo sells them but they cost about $130). So you would want to be real keen to do it that way.

In reality the best way is to take the tank off so you have good access to the carby and just undo one bolt and twist the carby make a small adjustment (quarter turn) bolt it back up and sit the tank back on and test it. Repeat until its right.