hi i had a problem in my carby that the mixture screw wasnt doing anything i finnaly fixed it it was just the adjuster inside on the accelarator was screwwed in too much what caused the carby to bypass the idle circuit!

anyways got that fixed now im trying to tune it i get good idle but when put in drive in shakes a bit and is gutless WOT until it picks up a bit! the micture scres about 2 and half turns out!

does this sound normal at WOT any more tips on how to tune??

Thanks!

anyone no???

sounds kinda like idle is too low, what's it idling at, should be at least 700, prob 800

last carby i played with the mixture was about 4.5 turns out

just take it to a mechanic and get em to stick the sensor up the exhaust, you'll save the tune up cost with better economy in no time anyway

which way does it lean and rich turning the screw my rpms are above 1000pm at idle coz once it goes to 900 it starts shaking bad in drive let alone 700 at idle would shake the hell out of me in drive!

dont know if its some problem or what i checked all the vaccum hoses and seem fine!

People have been tuning carby engines long before the 4 gas anayliser was invented.

Its not about how many turns out the mixture screw is. There are a number of things that contribute to an engine tune to get the mixtures set correctly. Timing, points dwell, even tightening the inlet and exhaust bolts are an important part of a proper engine tune. Spark plugs cleaned and regapped, all before setting the idle mixture.

Providing there are no manifold leaks allowing air in from unwanted areas, as the mixture screw is brought in, creating a lean mixture, the engine will start to run rough, then bringing out the screw will richen up the mixture, making it run smooth. Too far and it should also reachh a point where it will run rough. There should be a point in the middle that you can find where the engine runs smooth. Find a balance between that suits your needs.

But most importantly, the idle mixture is the last thing to do in an engine tune. Adjusting it for the hell of it is just avoiding another problem. Like adjusting your handbrake before adjusting the rear brakes.

damn i thought screwing the mixture in will rich and out will lean so its the opposite??

also my choke dosnt work at all when engine cold even if half way open just sputters and dies could this be if the mixture is to lean??

thanks!

It could be for any number of reasons..

out is more richerer

thank you
will try tommorow just stil dont no what to do about the choke not working!

If the motor is too rich at idle already, pulling the choke out will just make it richer still. The idle screw mixture should be set so you get the best vaccum reading, the old 120Y with an econometer was great for setting this, but otherwise try & get a vaccum guage & fit it to the inlet manifold, there's a couple of places you can screw in the fitting. Start with the idle screw about 1&1/2 turns out & let the motor warm up first before tuning it, just take it for a short drive round the block. You then turn the screw in for less fuel or out for more fuel. You can then use the screw on the throttle shaft to raise or lower the idle speed. If you've got an off idle stumble, maybe there's some rubbish in the main jet which is causing it to run like a diesel, if the fuel filter is old it might have failed & is letting rubbish into the carby.