Super Jet - Chasing Kinks

Z

zodiac420

Location
New Jersey
I have a '91 SN with a 61x 701 swap and twin carbs that I recently acquired. This is my first ski. I outline the progress I've made and what I have left to iron out and welcome all help.

First voyage: Super Jet ran fine on land for brief start ups and revs. Took it out to the river and it ran okay for a minute and died, but would restart with some prime. After 20 minutes of this, it decided it would not start up again. Checked it over on shore, came to this forum, replaced a faulty check valve and fuel lines.

Second voyage: Ski running good at all throttle ranges, but occasional hesitation/stutter like it was starving for fuel. This happened most often when throttling up from idle and turning left or right. Went back to the drawing board and discovered a leaky exhaust manifold. Replaced the gasket. Replaced spark plugs.

Third voyage: New check valve and exhaust gasket. Ski running what I would consider very well. Took it on a 20 mile trip up and down the river during which I noticed the following:
  • After stopping the ski for more than a minute, it would take a couple of tries to get running (i.e. turnover, start, die; turnover, start die; turnover, start, run). Three times seemed to be the charm on multiple occasions. The ski would idle fine when running with me on or off.
  • During the beginning of the trip, the ski would bog intermittently, particularly under constant throttle. I chalk this up to gumming in the carbs as this issue was present on the first two outings and seemed to disappear by the end of my latest trip, resolving itself.
  • Coming off of idle or low throttle I would experience slight hesitation or bogging - forget what fact pattern led to either condition.
  • Upon getting back to my truck, I checked the engine compartment and noticed a small air leak coming from the fuel selector (on the outlet side)
My plans going forward are going to start with tightening down the hose on the fuel selector. I'll probably it after that since I am not too excited to mess with the carbs. Does the taking multiple tries to start issue sound like an idle speed adjustment issue? From what I've read here, I believe the third issue has to do with pop-off which I'm a little intimidated by, but will see what I can find. Outside of this, when I go on vacation in a couple of weeks, I plan on sending my coil out for new wires.

Anything else I may be missing?
 
jetx

jetx

Location
Midland, Ontario, Canada
I’d be taking those carbs apart and confirming what jetting is in there and checking your pop off...sounds like a pop off issue or leaky needle valve to me. You can try everything else first but almost guaranteed you’ll have to get Into the carbs. They may seem intimidating but they are quite simple. Once you’ve done it you’ll have no worries doing it again and again.
 
S

SRQski

Location
Sarasota, FL
^^^^^ What he said.
New to you used ski = go through entire fuel circuit, especially doing carb rebuilds.
It's really not that hard at all and there's plenty of help here to guide you through them. You need to use Mikuni kits, no other brands. I'd replace the needle and seats in the carbs and maybe put new jets in as well so you know they are good to go.
You can do it!

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Z

zodiac420

Location
New Jersey
Alright, sounds like carb rebuild is in order. Since it’s not running 100% now I guess I’ll need the full get up with pop-off gauge and tach? I’ll look to see what factory jets are, I’d imagine it still has those as the motor is stock. Still a good idea to replace them if they are the factory ones?

Found a Mikuni dual rebuild kit with needles, seats, and base gasket for $140 which seems kind of steep. Is that the going rate?
 
S

SRQski

Location
Sarasota, FL
You can make a pop-off gauge for $15 if you have an air compressor to use it.
Don't have to have a tach but it's nice to have for fine tuning.
From my past findings Mikuni kits are $40-50 ea, N&S typically about $20/set, base gasket maybe $15 or so. IMO, the $140 kit isn't bad.

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