carb porblems after changing jets - no idle, poor running

[gttjames]

Right guys, car ran fine at 13psi, had a smooth consitent idle at around 14.1
Had off boost driving between 13.5-14
WOT saw around 11.9-12.4 area

Wanting more boost like most, so took carb off, left main jet alone, drilled 2nd stage to 1.2mm to start with and fitted a 1mm AC jet. Other than air linning the 2nd stage bit out after drilling and a spray with carb cleaner the carb hasnt been touched. The 2 gaskets i disturbed (2nd stage bit, and carb body bit) where all ok so refitted.

Put carb back on, and mixture screw, idle screw was in same position as i took off etc it started up ok but idle was abit low and on idle it was very lean going 17 and then off the reading, no biggie i thought it just needs adjusting, got it down to around 14.5 with the mixture screw wound right out, did a run in it and as soon as it got upto temp it wont idle and dies everytime im off the throttle. Tried adjusting the idle screw aswell no good, also removed the idle jet thing, the big screw on drivers side and made sure it was clear, no different.

Iv seen a 5 with no mixture screw atall in, just pluged up and its exactly like that, no idle, dies when off throttle. Obviously this put a end to any more fueling testing. Also i have a turbo from cr turbos, and im about 3 threads away from the end of max adjustment but boost hasnt really inscreased, actuator starts to open at 18psi when tested, but boost gauge in car wont go over a bar, boost leak?

with carb like it is, and boost set 18psi actuator, 14psi boost gauge im geting
no idle, 17+
off boost driving seems to vary 14-15
on boost it was mid 10's so very rich? and feeling very flat, I need to get boost up to cover this right?

Also my 5 with a scorpion with standard carb drove very well, no real pops on overun, now on over run thats all it does, pop pop pop pop

[tubbyG]

Defo sounds like an air leak.

have a look at the carb base gaskets and also that the carb base body is tightened up

[GTphil]

I know you mentioned that you have cleaned the idle jet out but you may find you need to do it a few times at least, your better off setting the mixture screw so it's rich at first and just getting it to run.

every single time i have taken my carb apart i have had to clean the idle jet at least 5 times, by pulling it apart and blowing through it making sure it's completely clean, over and over again then eventually it started to idle.

your symptoms are exactly what mine was doing, it's almost like a big air leak.

you may even find you get it idleing then as soon as you take it out for a drive the jet will need cleaning again, swarfe can be stubborn stuff;)

[gttjames]

Thanks, does seem like an air leak although strange its fine on boost (well rich anyway)

Iv had the carb off about 5 times when doing other work and bolted back on and no problmes, allthough this is 1st time iv opened it up, will try cleaning the idle jet over and over and see how i get on

[Tony Walker]

Spray some carb cleaner around the base of the carb, you should be able to hear the revs change as it sucks the spray in through a leak

[Woznaldo]

I'd check the seal of the Idle Jet. If the seal isn't perfect there, the idle will be terrible, if it idles at all.

[gttjames]

I'd check the seal of the Idle Jet. If the seal isn't perfect there, the idle will be terrible, if it idles at all.

But i havnt touched this area of the carb and it idle perfeclty before?

I will also try the carb cleaner method around carb

[gttjames]

Done the carb cleaner test and no rise in engine speed so suspect no leaks. I cleaned the idle jet out with a air line 3 times now and its idling... and running with no cutting out, so ok at the moment, cheers for advice!

In order to get an idle afr of 14 i have had to wind the mixture screw out 8 full turns - is that abit excessive?

Iv only done 3 miles in it to test it, but after my carb mods the crusing afr has dropped a little, i used to be 13.5-14 - now its more 12.9-13.5 (havent changed the main jet, only 2nd stage and AC so surely this shouldnt change??)

And WOT im geting 10.2 at 14psi so because of my 2nd stage now being 1.2mm i need to be running at least 18psi. My actuator doesnt look like it can go much higher as only has a few turns left. Should i fit this bleed valve i have here for the time being?

http://www.cgbmotorsport.net/cgb-under-bonnet-bleed-valve-lockable-1028-p.asp

[R5MJH]

Done the carb cleaner test and no rise in engine speed so suspect no leaks. I cleaned the idle jet out with a air line 3 times now and its idling... and running with no cutting out, so ok at the moment, cheers for advice!

In order to get an idle afr of 14 i have had to wind the mixture screw out 8 full turns - is that abit excessive?

Iv only done 3 miles in it to test it, but after my carb mods the crusing afr has dropped a little, i used to be 13.5-14 - now its more 12.9-13.5 (havent changed the main jet, only 2nd stage and AC so surely this shouldnt change??)

And WOT im geting 10.2 at 14psi so because of my 2nd stage now being 1.2mm i need to be running at least 18psi. My actuator doesnt look like it can go much higher as only has a few turns left. Should i fit this bleed valve i have here for the time being?

http://www.cgbmotorsport.net/cgb-under-bonnet-bleed-valve-lockable-1028-p.aspyeah do that but wind in fully then out slowly a bit at a time to test orherwise turbo may run to much boost and blow hg boss

[gttjames]

yeah do that but wind in fully then out slowly a bit at a time to test orherwise turbo may run to much boost and blow hg boss

cheers, so wind it all in 1st? and wind it out to increase boost

[R5MJH]

exactly mate half a turn a time but dont let afr go to lean keep an eye on it optimum is 12.1 mate

[GTphil]

That swarfe can be pesky stuff, I found a piece of silicone hose wedged inside the main jet the last time my carb was off:wasntme:

You might find it starts pissing around once you have done a few miles or give it some stick, just keep on cleaning the idle jet out.

[GTphil]

Bleed valves are ok for setting up with, the A/C will be what's making it as rich as 10.2 afr if your getting 14psi just of the actuator it won't take much bleed off at all for 18psi so be carefull.

[gttjames]

Now carb problem is sorted il continue in a new thread as its going different topic