2 replies to this topic

[Jc1991]

Hi everyone, I could do with some words of wisdom over my carbs. I bought twin su 1 1/4 carbs that needed some TLC I have stripped them down and tried to clean them up the best I could but I'm not happy them. How clean does the piston have to be. I have read to use carb cleaner and remove the black marks also How freely should this drop to the rest position ? Also the jet assembly feels very tight going through the bearing does the metering needle any adjustment? Any help would be massively approached due to basic knowledge of carbs. Thanks

Edited by Jc1991, 23 January 2017 - 03:45 PM.

[carbon]

There's a lot of good information on the web about servicing SU carbs. Some key points to watch:

- check throttle spindles for any wear. Normally with HS2 replacing the spindle sorts this without rebushing.

- check that both pistons are same time (4-5sec) in the drop test

- check dashpot springs are identical

- check needles are the same

Key thing here is to get both carbs identical, otherwise setting up properly will be a pain.

 

If the jet assembly is tight in the bearing try fitting a known good jet. They do sometimes get bent, then they won't move freely

[AlexMozza]

You want the whole assembly to be as clean as possible.
Any grit will cause parts to stick.
Could be worth getting them vapour or bead blasted.
Stick a rebuild kit in them and away you go!
As above make sure identical springs, needles ect are used.