Lean on idle? different needle?
Turbo Mini Forums

Hi

I've got the mini back in the road again.
Now I have a AFR gauge fitted. So I can see what's going on with the fueling.
I have a standard bdd needle in with transmission oil in the dashpot. On with a thicker spring.
At idle it reads blank ad in really lean. It doesn't idle happily either and has bad throttle response.
I've checked for an air leak but found no leaks.
Full throttle it spikes to about 10.2 then settles to about 12.
Is there a needle that is the same top end as the bdd but richer at idle and part throttle?

Thanks
Josh

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Well for idle you just need to turn the screw...

If it's jumping around afraid wise, I'd swap the plugs out, and also check the dashpot oil. Maybe thicken it up a bit.

Move the jet down a little?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Also, choke seals is a good one for screwing up the idle mix

What do you mean swop the plugs out?

I've got transmission 90 in. So it's thick stuff in there.

I rebuilt the carbon a few years ago and used the carb for about 500 miles.

Do I screw it in to ritchern it?

Thanks

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

pugs dont like getting wet with fuel, it can cause misfires, or just not firing at all, a misfire will skew the AFR , so its worth swapping the plugs for a new set to see if it makes a difference, basically always have a new set of plugs on standby, because you will get one go down at some point.

yeah, i'm sure its in to ritchen on the HIF's

If it is no better after new plugs have you not considered filing the needle ?

Set the idle mixture correctly then see what the fuelling is like when driving then. Once you've set the mixture at idle (screw in to make it richer & out to lean off) it's the profile of the needle that dictates the mixture elsewhere. If you find it's incorrect under load you'll need to start filing it.

Phil.

WWW.TURBO-MINI.COM

It doesn't sound like it's missing. But I have wetted the plugs a few times!
I've got the idle screw all the way in now and I've pushed the needle up into the dash pot a bit to richer it up. It's still a bit lean at idle. Showing 16 on the far, but as soon as I blip the throttle it goes richer and has better response.

Is there not a difervent needle I could try off the shelf beforeI start filing my current needle?


Thanks
Josh

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Hey josh
Avonbar sell different needles that are already filed down that should get you nearer.

Roy B

Thanks Roy I ordered a 14psi one earlier. Just hope it's a bit richer at idle.
Top end the bdd isn't far off.

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

There should be no issue at idle with a BDD , there's plenty of adjustment on the mixture screw. I doubt the Avonbar needle is any different at idle. I'd say you've got an issue elsewhere.

Phil.

WWW.TURBO-MINI.COM

Hmm I'll look for a air leak again but it seemed fine when I checked the other day.
What else do you think it could be?

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Right finally been able to drive this and have a play.
The avonbar needle didn't make a difference at idle as suggested above. It was too rich else where.
So put the bdd needle back in.
Again idle screw is fully in but it's still lean at idle.
When engine is cold and choke is out, AFR gauge sits bang on 14.6. As soon as it's warmed up and choke is in it reads really lean. Not even giving a number.
I'll try plugs next time I'm at the workshop.
I've got NGK 7''s in there at the moment. Is it worth trying a different type?

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

as phil says there should be adjustment to make it rich as fuck on idle, too rich to run in fact.

I would have the dash pot of and check the screw is moving the jet up and down in case the is an assembley problem ( unlikly though)

could it be that on choke it has a lot of throttle adjustment? look to see how far the throttles opening when on choke, are the revs high on choke?

try easing the choke in in stages and adjusting the mix and idle as you go?

The jet does move i did check.

Think when chokes out to where it like's to start (when cold) it's revving at 2000rpm. But I'll check.

When I first put the carb on it would rev loads but I adjusted the throttle adjustment on the choke.

I'm wondering, is it possible that it's actually rich at idle but the AFR is going well off scale?

What's the best/safest way to find a air leak? I know about spraying wd40 on the joints but a bit worried about it catching fire. Or am I just being a wimp lol

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

wd40 is not that flamable it will be fine,

I was thinking the same about it being too rich, as sprocket will vouch the labda gauge is really more of an oxygen sensor and not a mixture gauge, if you have a rich misfire it could start reading leaner again, but I'd expect it to be retty erratic,

Ok. Plenty of things for me to try before taking it to bits then.
I'll screw the mixture screw out a bit and see if it makes a difference.
Then try wd40 on all joints.
And the spark plugs but I don't think it is the plugs. But worth a try I guess.

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

Ok the mixture screw is in tight. But its still showing lean off scale on my AFR gauge.
I turned it so it leans it off to rule out it being over rich and throwing gauge out but it coughs and splutters and stalls.
Is there a way to measure full lift of the jet? I'm wondering if it''s not moving fully if that makes sense?
It definitely moves though as I've checked..

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

OK, how far below the surface does the jet get, it should basically get to flush, which would totaly shut the fuel off,

Maybe check the choke seals.

Going back to this.
Would choke seals cause it to run lean?

As it is, the mixture screw is in fully (rich as possible).
If I screw it out it starts to cough and splutter.

I'm thinking about filing the needle a bit. Is it the base (fattest bit) of needle that does the idle?

Cheers
Josh

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985

I would go with what has been suggested quite a few times!

Don’t touch the needle. There’s something else wrong. Check for air leaks.

I can't find any air leaks though.

I thought if it was choke seals it would be the other way...too rich??

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985