5 replies to this topic

[spaulwill]

I can anyone give me some pointers where the screw settings should be for initial start up. I am running 1 1/2" twin SU, i have set the jet to 1mm below the bridge as per SU manual but am a little confused by the other two adjusters, the one which I believe is the throttle stop is at the moment turned right back and is touching the lever, the other screw which I believe is the idle speed is just touching the 'choke' lever i did read somwhere 1 1/2 turns down but cant remember which one. any help appreciated as always as i would like to start her tomorrow, currently on M needles but have a choice of AH2 and MME too with red or blue springs. The other thing i noticed is that on my 1 1/4s there was a breather attachment on these there isnt is this an issue, there is no vacuum either. the carbs have been fully rebuilt with the correct fuel bowl angle as these proberbly were not originally off a mini.

[jaydee]

1 1/2 turn down from flush is the jets if they're the old type, new type is about 2 1/2 turns

Which is about 1.5mm from the bridge by the way

Set the idle screws to the point the just open the throttle butterfly, you'll set them properly while balancing the carbs.

Choke lever and fast idle screw set about 5mm clearance

Make sure the breather in the carb is blocked if no pipe attached.

Hope you already checked dashpot/piston assembly, dampers and spring if they're all matching.

M is quite a 'normal' needle and similar to AAC, AH2 is richer and MME is bloody rich, suitable for engines that breathe a lot using an induction system like ITG etc..

[spaulwill]

yes thanks all refurbed and new springs, oil. there is no connection for a breather on the carb. is his a massive problem?

[jaydee]

Depends what breather, you could have a few: crankcase, dizzy vacuum, servo vacuum..

if for crankshaft ventilation, you have to route it somewhere else (air filter) no problems though.

[carbon]

+1 for all of Jaydees comments.

 

Suggestions on needles wil depend on what engine spec you're running.

 

If you use blue springs the needle will need to be thinner (ie richer) at just about all stations

[spaulwill]

engine spec, 1293 , s head, 1 1/2 su on M at the moment with osselli inlet, aldon yellow, road/rally cam, 4:1 FD, maniflow manifold and RC40.

i have red springs, ah2 and mme needles also to change if needs be