34 replies to this topic

[crackfoo]

For twin HS4s the AAA swing needles are a pretty good starting point. Very similar profile to the number 7 fixed needle which was supplied by BL in their Special Tuning twin HS4 set in the early-mid 70's.

 

Would recommend taking a close look at the dashpot springs and the damper. For your set-up I think the blue springs will work best - reds are likely to make it way too rich.

 

For the dampers the twin HS4s normally use the AUC8114, rather than the AUC8103. If you look on the top of the black plastic damper cap you should find the numbers.

 

I've found that the Twin SU HS4's on my 1380 are from an MG (AUD325A). Would that change anything in regards to needles and springs?

[carbon]

AUD325 would originally have red springs fitted, yours will likely need blue springs. The needles have been changed already, also the pistons and dash-pots may be from another carb as the 325's would originally have fixed needles.

 

Check both springs are exactly same weight, otherwise you will never get the carbs to balance properly.

 

PS. float bowl tags should be 325R and 325F

[crackfoo]

Ok thanks for the clarification.

The float bowls list AUD325AF & R

You mean check the existing springs? They seem to balance fairly decently on idle but I have no idea what ones they are.

[carbon]

If you're going to replace the springs with new blue springs then would not worry about checking the existing ones.

 

Imbalance in springs more of an issue at med-high rpm

[crackfoo]

ok thanks for that. Will track down a set a new springs and needles and go from there. Also have a new set a jets to put on.

Edited by crackfoo, 13 December 2014 - 03:29 AM.