[zukmeista]

1. I want to know if a sierra carby can be modified so that the secondary system is mechanically operated. I don't think the vacumn system is working and I would prefer a less complicated system.
2. I have a K&N filter and extractors with a 2" exhaust. Would I get more power by fitting bigger jets? If so, what size should I use?

[neofitou]

Modifying it to be mechanical would be much harder than just fixing it.
Hows that for less complicated..

[zukmeista]

Don't like the vacumn idea, too much to go wrong.

[neofitou]

as opposed to trying to adapt something from a different carby that was not designed to be fitted to this one, with more moving parts than the vacuum system?


I was trying to find a usefull image, but this is the wrong side and not helpfull so I should shut up now..

It would be cool if there was an easy and reliable way to have it mechanical, it was good on my old webber as you could actually feel it opening through the throttle cable.

[zukmeista]

Yes it would be, this is what I am trying to find out

[UBZ]

section 4 of the FSM.
the secondary butterfly is enabled by a vaccum actuator. then the secondary butterfly works in tandem with the primary butterfly.

so In theory you could fit a choke type cable to activate the senconday butterfly instead of vaccum actuator............

but would result in over fueling at low load if you forgot to turn it off.

if your secondary system is not working well ,then i would check the vaccumm conection or reco the carby.

I'm sure Zookyman can help you with carb bits , if he can't I'm pretty sure I gof a couple lying about the place.

[Jackson]

From neofitou's picture it looks like the sierra carb uses the same actuator as other Aisin carbs.

I did at one stage hold the actuator open with a spring, if you look closely there is a couple of bits that stop the secondary opening even if the actuator was open so the secondary can only start to open at about half throttle...

I thought it made it a little unresponsive once the secondary was opening.

Though I haven't tried this again since I rebuilt the carb so I might try it again just for fun.

[zukmeista]

I have checked the hose connections and the diaphragm holds vacumn but the vacumn port appears to be inside the secondary barrel? How does that work

[Jackson]

I don't know I have had a look while it was apart but I couldn't find where it went to. The port that goes to the diapragm is only a pin hole too. I toyed with the idea of running it to one of the ports that I blocked off that are the same size as say the dizzy advance...

From what I have read the diaphragms only have a life of a few years as they get tiny little holes in them and I suppose the fact it is being supplied by a pin hole these little holes would affect its ability to open.

[JrZook]

You will find that even if you are able to connect the secondary up mechanically that you will experience a huge flat spot or bog down when it opens.

This is due to the vacuum secondary design of the carb and thus it does not have a secondary accelerator pump or transition ports/jets which will cause a nice stumble when opened manually rather than by engine load.

Dan

[zukmeista]

Well what needs to be done or checked to make the vacumn system work properly? What other carbs have mechanical secondaries?

[UBZ]

dude ! section 4 of the FSM - (feild service manual)
Suzuki Info website

[zukmeista]

All that says is to check that the diaphragm holds vacumn, which it does.
Would this work on my sierra?weber carby

[zukmeista]

Come on! help me out please

[jdk81]

Webber carbs create more problems than they solve.
I know some people have a hard one for them, but most prefer not to use them.

In my opinion theres 3 options.
rebuild your carby and get it running right
a SPFI conversion
or put up with it, and save your $ for mpfi (g16b)

[Daves4wd]

I had a Nikki 4 barrel carb on my rx7 and the secondaires never would never open took it to get a rebuild and it's was a small hole in the diaphragm and the vacuum line in the carb was blocked it's always good I rekon every few years being a 4wd to get it rebuilt or cleaned as dirt gets everywhere in them and there and small hole needless to say now it runs like champ but it's just all on personal preferences

[JrZook]

zukmeista wrote:

All that says is to check that the diaphragm holds vacumn, which it does.
Would this work on my sierra?weber carby

Yes it will.

In regards to your stock carby, if the vacuum pot is holding vacuum then check that the vacuum port it feeds off is clear and not clogged with carbon build up

[ROAR99]

zukmeista wrote:

1. I want to know if a sierra carby can be modified so that the secondary system is mechanically operated. I don't think the vacumn system is working and I would prefer a less complicated system.
2. I have a K&N filter and extractors with a 2" exhaust. Would I get more power by fitting bigger jets? If so, what size should I use?

swap secondary fuel jet into the primary hole ,then drill out primary jet to same size and drop it back in the secondary hole.. you can just swap jets over but it wont want to rev past 5,000rpm.. this will give u better takeoff ..
if its a daily driver u cant go past a webber for power increase.

[zukmeista]

I ended up putting secondary into primary and a 140 into the secondary.