Setting up and needle selection on a 998 stage 1. *Any help today near DY5?*
Turbo Mini Forums

Right, now the gearbox seems to be okay after swapping it (to a known good box) I've got to get the car to drive properly.
The mini is fitted with a hs4 carb, K&N cone filter and a full maniflow single box centre exit exhaust system.

Now the needle that came with the car was an AAA, which was used to drive to the MOT station and back (poorly, the mot emissions test it was practically running on thin air) I have tried an AAM needle (which originally came on the car the gearbox was off, and my mate now has the carb and it was setup on the rollers with a K&N cone and twin box rc40 on a 998, and I also have an AAC needle (standard needle I think?) They all produce sewing machine like idles, but as soon as you apply any load the engine stalls off and dies. Which needle is best to use to start off with? Not sure if its running lean or rich atm and the hs4 is a pain in the arse to setup. I've adjusted the timing and have a timing light so I don't think that is the problem. I don't have any fuel to the carb issues either. Pulling my hair out, help!

Edited by Carlzilla on 17th Jul, 2013.

If I remember rightly I think I fitted a AAU needle in my stg1 998. I also started from the jet fully wound in then backed off either 1/2 turns as a starting point.

Edited by TomBooth on 16th Jul, 2013.

Yeah AAU I had in mine too, but I read somewhere that's stage one 'lean' and AAM is stage one normal and AAA is for use with a mild cam change?

i have not long since set up a local lads stage one 998, the needle ended up almost exactly the same as an AAU
however he came back when it was cold and i put a touch more fuel in stations 8-11
it ended up quite a rev happy engine :)

Yes i moved to the darkside

Instagram @jdm_brett

mintylamb.co.uk


AAM is leaner than AAC /AAA/ AAU
i wouldnt use it... ( unless i could tell the engine wanted it)

Edited by Brett on 16th Jul, 2013.

Yes i moved to the darkside

Instagram @jdm_brett

If im looking at this correctly, the AAU is leaner all round than the AAM and AAA but the AAC is mega lean?

I think the AAA might be my best bet.

Edited by Carlzilla on 16th Jul, 2013.

congrats on the box bud
AAA and what fuel pump are you using?
had a mechanical one that was working but didnt pump enough through on my 998 (5 years back now :o)
check out the fuel pressure into the carb

**EDIT presumed it was a turbo lol**

Edited by WRLondon on 16th Jul, 2013.

Reading up on RTS Clutches

Yes i moved to the darkside

Instagram @jdm_brett

looking at these figures ( of the 998 i did) the curve is almost exactly the same as the AAA ( you notice the curve change @ station 8)
except the needle i did was 0.1mm leaner across the whole length that could be factored out with the base jet hight

Yes i moved to the darkside

Instagram @jdm_brett

The last part made me laugh, if he has his way I think it would have been a turbo .

On 16th Jul, 2013 WRLondon said:
congrats on the box bud
AAA and what fuel pump are you using?
had a mechanical one that was working but didnt pump enough through on my 998 (5 years back now :o)
check out the fuel pressure into the carb

**EDIT presumed it was a turbo lol**

They don't die, they just get faster!

Well I'm stumped. Got it to accelerate great at standstill in neutral, then took it out on the road and *hfyudghyvgyu* bogs down and no power, if you lift the throttle up slowly theres a spot where it just lurches forwards into life and dies, and lurches forward. I've been faffing with the mixture both ways but I still can't get it to do what I want. If anybody is local tomorrow I would highly appreciate a second set of senses to help out and diagnose what the hell is going on :(

I have the full minispares twin-box RC40 on my 998, originally had a AAU which came with the kit, but found it would bog down slightly at full throttle.
Now switched to an AAA and its much better, I can't remember how I set it up - something along the lines of a colour tune until idle was about right and then a tad richer.
Also as it hasn't been mentioned it may be worth playing about with dashpot oil, maybe try something a little thicker.

Also when driving try pulling the choke out a little and seeing if that helps, as that will help if its lean, but won't help a great deal if its a transient issue (i.e. dashpot oil), and will make it worse if its rich.

Choke makes little to no difference, Dashpot oil ive tried 3 in 1 and 20w50. Revs fine in neutral all the way up now, but still shite under any load.

Do you have a wideband?
If you set the mixture 2 full turns richer does it still do it?

Yes i moved to the darkside

Instagram @jdm_brett

I don't even have a rubber band, nevermind a wideband :/
At least i could see what on earth was happening then!
Gonna block off any potential air leaks and try again today.

stupid question but have you checked the carb float to make sure it's set right?

Carb float is right checked that a dozen times and its operation, ive been down to my mates and took his dashpot and piston off and measured how far down his jet sits from the bridge and set this carb the same (similar needles and his has carb been rr tuned) Timing makes no difference, blocked off the breather and vac advance with my fingers makes no difference, the vac advance works, jet isn't blocked. I'm gonna put up a couple vids now, one not on choke and one on choke so you can all see/hear what it does (which is pretty much idle and that's it)

Engine is up to temp...
Idle - https://www.facebook.com/photo.php?v=102006...299668669421883
On choke - https://www.facebook.com/photo.php?v=102006...304820637337747

Oh and theres 20w50 in the dashpot

Yo vids doe work!

They don't die, they just get faster!

Oh well. Ive found after much ballache that the carb is at fault. It's not pulling enough fuel through so I'm going to investigate that now. First off i pulled the filter off and put my hand over the inlet practically covering it and the engine dramatically changed. The fact the choke does nothing suggests a blockage or restriction between the jet and float bowl. Popped my mates known working carb on, and jobs a good un! Not quite suited to this engine but I'm not going to mess, at leasylt i now know the problem!