As you may aware, I bought the carburetor SU HS6 as a complete unit, it comes with BAK needle and green spring, and that what I use for the initial set up… It works but may be not optimal… from the forum and discussion, they are few suggestion:
- Copy ACR set up with BGB needle and Black spring
- BDM needle with red spring
- BDB or BBW but not sure what spring they use..
Just to remind you on the profile of the needle, you can see below that BGB is very rich needle, BBW second, BAK third, BDM fourth and BDB is the leanest…
Actually I want to copy ACR set up, however after having discussion with Burlen… there is no such thing as black spring for HS6, I think they do not want to be copied, and may be they change the color of the spring to hide the their set up…
Finally I ordered BDM and BDB needle and red spring, hence I have three needles and 3 springs (one spring is from old SU)… it will be interesting the try all possible combination.. :).
Here some photos when I am tried needle and spring combination
To make it apple to apple, first I have to make sure that the ignition timing is at 6 deg BTDC as suggested by ACR using their Cyl head.
So.. after the few tries… I finally concluded that the setup is best using green spring and BDB needle... The others also works but at high throttle it missed fire or blow back… or severely lost power compare to this one. it is quite strange… ACR set up is using the richest needle, I am using the same head from ACR but it best using the Leanest of the option…
Bit confuse, but I find it very smooth and have more power using this set up, it capable of going uphill at 3rd gear, previously it need the second gear to climb it… So thats it for now, any questions please write it down below.. hope it can be useful for you
Cheers for now..
Other set up is OK, but in the open throttle, I experienced a missed fire… even if I tried my best to adjust the