How to Build & Power Tune SU Carburetors by Des Hammill

[KWM338R]

I checked the fuel level in my jets last night and was amazed at the difference. The front carb had the fuel level about 1/16" below the top of the jet, the rear I could hardly see down the jet, i.e. it was very low. Had a hell of a job trying to level them out, I managed to get the front level to drop but couldn't really get the rear to come up much, I even ended up putting two gaskets on the rear float lid. What should the level be or doesn't it matter as long as they are even?

Cheers
Mark

[Stevecox]

Found out the other day both carbies on my sprint where fitted with front float bowls (AUD 2140)
Correct part number for rear carbie is (AUC 1310 )
It raised the level in the rear carbie by about 5mm
Worth checking

Steve

[Jon Tilson]

The float level with plastic floats is non adjustable...

So how do you adjust it?

If the level is wrong or different in your jets its probably becuase the waxstat pellet is failing...

Jonners

[jeroensprint]

When it is not possible to get the floatlevel ok in both carbs you can use different floatchambers. A dolly engine is hanging backwards and the carbs too. some others cars with su's have floatchambers with another mountingpoint, lower, so your floatchamber is getting higher on the carburettor and so you can adjust the floatlevel without overfloating to get the rear carb right.

[Keith CANSDALE]

I measured the difference horizontally between the carburettor bridge and the float levels at being 10-11mm (higher in the front one), with a spirit level. I then lengthened the front float needle with a 3 mm piece of 3/16th piece of brass pipe held with a drop of loctite and it worked! The motor is noticebly smoother. How could the manufacturers haveoverlooked that? Is a longer float needle available commercially for this?

[Stevecox]

Thought along the same lines about different length float needles
and checked with SU Midel http://www.sumidel.com/contact.htm
but all needles are the same length
Would it be possible to make up offset solid carbie mounts to both lower the front carbie and raise the rear carbie to get them level

Steve

[KWM338R]

Thanks for the input gents. I changed the floats to the brass type from some HS8 i have and was able to adjust the level to get closer to equal height. i do not have waxstats so that is not an issue. I have another problem right now that I have to address before I go any further, my right engine mount has colapsed so that is definately not helping!

Cheers
Mark