Super Jet 1990 sn with a 701 61x-missing 600rpm

C

Connor1998

Location
Pinellas, florida
i recently bought a sn superjet that has a 61x swapped in, runs, starts fine, but i put a tach on it to help me tune the carb- it was running super rich and it only spins ~55-5600 rpm. my understanding is that these are supposed to spin 6250-6350 rpm. this has the stock 650 waterbox in it, would that be restrictive enough to cause the drop in rpm, or could a better tune fix it? i belive this also has the stock impeller, though it has a solas yb- something intake grate. any help is appreciated, im pretty broke right now so ill try all of the cheap solutions first. (i read somewhere that you can drill out something on these sn boxes to make them breathe better)
 
C

Connor1998

Location
Pinellas, florida
mikidymac said:
If you don’t have a tach then how do you know it’s only reaching 5600rpm?


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i do have a tach, iput the tach on because i thought it wasnt going as fast as it should be after i tuned it- the tach confirmed what i thought; flat out with all my weight off the back of the ski trying to go as fast as possible i only get 5600 rpm. some new developments though, i tried tuning it again last night and i found out the carb is over jetted, i can lean it out all the way and still get no midrange hesitation and i currently have the high speed jet set about half a turn out from all the way lean. i can give it a half turn in either direction and have no measurable change in rpms at WOT or change in midrange throttle response. i looked at the impeller to make sure it is indeed stock and it has a few knicks in the leading edge of the blades-3 knicks- one on each blade no larger then a bb. the wear ring clearance seems to be okay however. also, i found a water leak on my stock exhaust, small hole in the upper part near where the rubber hose to the water box starts.
 
jetx

jetx

Location
Midland, Ontario, Canada
Your first post says it’s running rich, and you just confirmed it again...get into the carb and confirm it’s jetted right and that everything is set and working as it should.
 
C

Connor1998

Location
Pinellas, florida
jetx said:
Your first post says it’s running rich, and you just confirmed it again...get into the carb and confirm it’s jetted right and that everything is set and working as it should.
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okay, what do you suspect the jetting needs to be at? stock 61x, single mikuni 44 carb, stock exhaust, stock flame arrestor.
 
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