19 replies to this topic

[rodomo]

You couldn't afford me.

[EunUCh]

Hanra should be able to help out a bit on this one?

 

Never had a great deal to do with them myself but first thing you need to do is get em in sync.with correct float setting,from memory there is two types of floats.

Take air cleaners off and use a piece of plastic tube to the ear and and place other end of tube somewhere near slide so

that you can hear the "pop" of induction noise,adjust the butterfly synchronizing adjusters till they all have the same level of noise.

 

The big nuts underneath are usually wound all the way up and then backed off so many turns as a starting point,dont remember the number of turns to be backed off,might be about 1-11/2,not sure.The nuts are used to adjust the idle mixture and you must take note  how far you turn each one from the starting point so as to keep them even,you are actually moving the main get up and down when you adjust these nuts and if they are not all the same height it not only affects idle but also main mixture.

 

Getting the right size needle can be a bit tricky because there is quite a few available, start with something from an engine with  similar sized cylinder that uses similar carb is what I would do.

 

The spring and dashpot oil weight also determine how rich or lean the carb will run.I could be wrong here but I think heavy spring tends to make them rich because the

piston has more weight to fight and  thus wants to hold the piston and therefore the needle down which causes a strong signal at the venturi which pulls over more fuel for the

amount of air being used.

I figure the oil would have more to do with dampening how quickly the piston rises when accelerating and therefore affects not only off idle but also main mixture during the transition therefore affecting the entire fuel curve to some degree.

 

Not sure if that helps at all

[hanra]

No balls is pretty much on the money. What type of SU's are they? Float level is very important, as it determines how far up or down the jet the fuel sits.

I usually wind the mixture nut all the way in then back off 12 flats or 2 full turns as a starting point. Singer oil to ATF fluid is the about the viscosity choice for dashpot oil. Massive range of needles to choose from, couple of different springs also.

Honestly, to make things a lot easier you need to get these:

http://www.ebay.com....=item51b06a1526

[hanra]

^or just read the above link

[Dave6179]

No balls is pretty much on the money. What type of SU's are they? Float level is very important, as it determines how far up or down the jet the fuel sits.

I usually wind the mixture nut all the way in then back off 12 flats or 2 full turns as a starting point. Singer oil to ATF fluid is the about the viscosity choice for dashpot oil. Massive range of needles to choose from, couple of different springs also.

Honestly, to make things a lot easier you need to get these:

http://www.ebay.com....=item51b06a1526

Exactly! I've been using my ColourTune for about 26 years. I used to read the plugs but that was taking too long and using fuel. The CT takes 10minutes to check all three SU's. I use 'TW' needles. I also use a plastic tube to balance the induction noise.

[Dave6179]

Heres something else you may want to read at least twice.

http://www.sw-em.com/su_carbs.htm

[hanra]

Adjusting the mixture nut will not help in anyway at all if it has the incorrect needles for your application. I think the majority of needles all use the same diameter for the first few stations which basically covers idle, but after those first few stations everything changes.

[hanra]

http://www.terryhunt.../picsb/pics.htm

[hanra]

I can see 353 needle variation for a HS2 SU with a 90thou jet.

http://www.teglerize...esortjava2.htmc

Edited by hanra, 18 December 2013 - 03:53 PM.

[warrenm]

OA6 needle...

So will i be safe to turn them all in then out two full turns and go from there? I just want it to stop fouling the plugs and clean up the exhaust smoke a bit. 

I find the best way is to remove the bell, piston & spring, one at a time, the wind the jet up till it's level with the bridge, then wind the jet down 2 full turns(or .050" if you have a set of verniers). Put the piston,spring & bell back on, then do the next carb. OA6 needles I think are a bit rich, but that's what you have till it can be run on a dyno or some other means of testing.