Help with carb differences

[Blitz]

Following from my receipt post I going to order new jets and needles. 

According to SU web site my Spit4 should have a AUD 983 carb with a 9104 jet and a AN standard needle. 

However I have an AUD 285 ( listed as USA Mrk 3 not UK ). The jet assembly is however the same AUD 9104 but with a DD Needle. 

Anyone know of any major differences? And should I still use a AN or DD needle? I’m guessing AN due to my smaller CC engine?

thanks 

Grant 

[Pete Lewis]

Have a browse at http://www.mintylamb.co.uk/suneedle/

This  allows you to see the plotted profile variances

Pete

[Blitz]

Thanks pete. Looks nice but means bugger all to me 🤪😂

 

[Pete Lewis]

If you input the two needles it produces the graphical  ramped steps that define the taper of the needles at ten points along its length

There is not much difference between AN and DD  the two are not miles apart.

Pete

[Mad4classics]

The other difference between AUD983 and AUD285 is the different damper fitted; AUC8114 vs AUC8103 - these give different piston rise rates.

It's  easy enough to change one SU carburetter spec to another.

David

 

[Pete Lewis]

So to really correct the spec you need to replace the  needle and dashpot  damper

Is there a running problem with whats fitted ...????   

 you can soon spend a few £££s for little in return 

Pete