16 replies to this topic

[Laps1999]

I have a 998 classic mini that I race . At the moment I have a red jet with an AAA needle in but it's putting to much fuel in and it's chocking the plugs up . I have wound it all the way in and it still dose it . So is there any thing I can do ? If not what should I use inserted

[Minigirl]

Clockwise richens on a HiF carb, which one are you running? 

Edited by Minigirl, 07 June 2014 - 09:50 PM.

[Laps1999]

So the nut on the top of the jet the gold one needs to be turned out ?????

[Laps1999]

Clockwise richens on a HiF carb, which one are you running?

it's a su carb

[KernowCooper]

Top nut on the bottom of a HS series carb secures the jet, the lower one adjusts the mixture, is the engine completely standard ?

[Laps1999]

Top nut on the bottom of a HS series carb secures the jet, the lower one adjusts the mixture, is the engine completely standard ?

. As fair as I know it's standard

[KernowCooper]

Mixture is the last thing to adjust once you have carried out a basic engine tune, tappets,plugs.points timing and air filter

[Laps1999]

What

Mixture is the last thing to adjust once you have carried out a basic engine tune, tappets,plugs.points timing and air filter

. What do I have to do to them ATM I'm re seating the valves on a head what will be going on it . But when every I race the car runs ok but after a couple of races I have to put new plugs in because there choked up and won't work .

[KernowCooper]

You ensure all those settings on the engine are setup correctly otherwise you cant set the mixture correct

[Laps1999]

Yer there all fine it has new points and router arm all the time it has a kaN cone air filter it runs good when it has new plugs in just after a race or two they start to choke up

[KernowCooper]

Then set the mixture at idle to 3% and try from that starting point, if its still rich then check the float level, It may be set rich to compensate for the K&N which on a standard needle you may have flat spots in which case you would need a needle change

[Laps1999]

Thanks but how do u even se it to 3% I don't really under stand how to set a carb up . just let u know I'm only 15 :)

[KernowCooper]

On most models, HS Series of SU the jet adjusting nut is clearly visible beneath the body of the carburettor. Turning this adjusting nut upwards (tightening) will weaken the mixture and turning it downwards (loosening) will make the mixture richer. You can obtain an SU jet adjusting spanner to make this adjustment easier.  If your mixture is really badly adjusted you can tighten the adjusting nut up fully and then loosen it 12 flats of the nut. This will set your mixture to approximately the correct place.
 

 Use the lifting pin method as below which is in the lower carb body

 

Raise the lifting pin to lift the piston by approximately  1/32 in (0.8mm).

• If the engine speed increases, the mixture strength of the carburettor is too rich.

• If the engine speed immediately decreases, the mixture strength of the carburettor is too weak.

• If the engine speed momentarily increases very slightly then returns to idle, then mixture strength at the carburettor is correct.

Or set it with a Exhaust gas Analyzer

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Edited by KernowCooper, 07 June 2014 - 10:45 PM.

[Minigirl]

AAA is quite a rich needle as well if you have a standard setup...

[Minigirl]

AAC is the stock needle for a standard 998 

 

use http://www.mintylamb.co.uk/suneedle/ to see the difference between the AAC and the Rich AAA needle you have