Super Jet Carb / idle question (my ski won't idle even with the pin and throttle cable out)

slamb33

slamb33

s
Location
NorCal
I am a bit of a beginner when it comes to carbs, but hopefully this is simple.

1999 superjet with 760 cases. Stock 701 carbs.

I had the carbs rebuilt at a local ski/bike shop, and when everything was put back together (at the same shop), my slowest idle is now not an idle at all, it is like 1/12 throttle.

Even if I remove the idle pin, unhook the throttle cable at the carbs and manually twist the throttle as far to closed as it will go with my hand (it is not hitting the stop), it still runs really fast.

When I look down into the carbs, the throttle valves are open only a tiny bit, but I guess more than they should be (I don't have a reference point for how open they should be).

So, what do I have to do in order to adjust the valves so that they seat to a full closed position inside the carb? Once I get them seated, I can adjust the idle pin to a proper idle speed...

Many thanks for any advice.

Steve
 
A

aramis

Location
Rochester, NY
bent butterfly valve(s) due to a backfire? sucking air around the butterfly pivot bushings?

Also, are you sure that the revving is really due to the carbs / butterflies and not a lean run-away condition? dry carbs will do that at first after a rebuild until they get full of fuel. And, if your jets / adjusters aren't set right it will run away too. When that happens it's more like a "holy crap, may engine is going to explode!!!" thing instead of a "hmmm, I gotta adjust the idle" thing, though. Typical way to know for sure is that a lean run-away won't shut off with the stop button...you've got to pin the throttle full open to feed fuel to cool off the plugs while hitting the stop button.
 
slamb33

slamb33

s
Location
NorCal
Hey thanks for the reply. It is not a "holly crap my ski is going to explode" (which I have experienced once) and I can easily switch it off with the stop button. The carbs were done a while ago and the high idle isn't THAT big of a deal when the ski is in the water, but on the trailer it is very apparent. I've been ignoring it and started to mess around with it yesterday a bit which is why I decided to post... Both butterflies are equally open when I look inside, so I don't think they are bent....
 
swapmeet

swapmeet

Brotastic
Location
Arlington TX
Could be the setting of the low speed screw.

How does the ski run once on the water? If the LSS is closed to much it leans out the mixture causing higher idle with the air thats available. The other possibility is the carb gasket. You may have a tear or other slight air leak thats letting a minute amount of air in after the carb.

It'll likely get worse before it gets better, probably a good idea to address it now.
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
I'm guessing the shop put the throttle plates on in reverse to where they won't close fully.
The edges are angled and will fit right only one way.
When they are properly installed and closed, you should not see any opening at all.
 
slamb33

slamb33

s
Location
NorCal
Ski runs okay in the water, I get a slight bog sometimes when I gun it - depends on how open the throttle is prior to hitting it. So, I suppose it could be that the mix is too lean. I will mess with that over the weekend. Thanks for the input. If not, will get the gaskets replaced. Appreciate it.
 
You must log in or register to reply here.
Top Bottom