Carburetor (specs) Database: SuperJet and Blaster 1

Joined
Feb 19, 2013
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4,087
Location
Chico California
Basically your prop is peaked at 3/4 throttle. could pitch up a bit. It is pushing all it can.
Interesting. I run a 10/16 hooker in my a/m ski with the same pipe and dual 44's and she just keeps pulling. I will try a different/ large hub impeller next. Thanks!

*currently running Solas 14.5/18
 
Joined
Dec 22, 2006
Likes
100
Location
MotorCity
Finally got around to tuning my boat in flat water and noticed that I have no difference in power from 3/4 - full throttle. Any ideas?

754cc
ported cylinder
blue printed pump w/ Solas 14.5/18
stock 38's no choke, OP flame arrestors
80 low
135 high
95g spring, 2.0 needle seat

TNT piped tuned to sizzling hot chamber, 2mm stinger hole, headpipe is cool/warm to touch.


*Ski is like a rocket going from 0-3/4 throttle though. :)
your going rich(?) did you turn in the screws and see if RPM gains? my experience with good ported setups jetting numbers are leaner than 80/135 because of the increased efficiency (draw or velocity) of the system. Tune on peak RPM

Example: Same motor
58 mph with 38's could be 70/130
58 mph with 48's could be 140/140

48's will get you their faster but require more jet because of intake velocity.
 

Tyler Zane

Open Your Eyes
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Joined
Jun 2, 2010
Likes
486
Location
Panama City Beach, FL
Square nose, -3

Brand = mikuni
Model = retail
Size = 44
Quantity = 2
Main Jet = 132.5
Pilot Jet = 120
Needle/Seat = 2.0
Spring = 80
Pilot screw =1.5
Main Screw = 1.5
- - - - - -
Gas Octane = 93
Altitude = sea level
Main type of riding = freeride
Would it pass the 10 second WOT test = always wot
Powerband = mid to high
Motor type/setup = ada head 35cc domes, 701 62t cylinder, 62t cases, oem intake, carbon tech reeds, b pipe mod, (All screws closed, spray bar in head pipe), msd enhancer, stock flame arrestors with 2 screens, 148 mag, 9/15 solas.

Ski runs absolutely great. Never skips a beat, pops right off and will idle across the lake. Best running ski I have tuned from scratch and I'm proud of it.
 
Joined
Feb 19, 2013
Likes
4,087
Location
Chico California
your going rich(?) did you turn in the screws and see if RPM gains? my experience with good ported setups jetting numbers are leaner than 80/135 because of the increased efficiency (draw or velocity) of the system. Tune on peak RPM

Example: Same motor
58 mph with 38's could be 70/130
58 mph with 48's could be 140/140

48's will get you their faster but require more jet because of intake velocity.
Good to know, I was under the assumption that larger carbs/more air would increase mph and rpms. I will take out the tiny tach and gps this weekend and play with the screw settings/jetting.
 

Big Kahuna

Administrator
Joined
Jan 14, 2006
Likes
5,820
Location
Tuscaloosa, AL
Square nose, -3

Brand = mikuni
Model = retail
Size = 44
Quantity = 2
Main Jet = 132.5
Pilot Jet = 120
Needle/Seat = 2.0
Spring = 80
Pilot screw =1.5
Main Screw = 1.5
- - - - - -
Gas Octane = 93
Altitude = sea level
Main type of riding = freeride
Would it pass the 10 second WOT test = always wot
Powerband = mid to high
Motor type/setup = ada head 35cc domes, 701 62t cylinder, 62t cases, oem intake, carbon tech reeds, b pipe mod, (All screws closed, spray bar in head pipe), msd enhancer, stock flame arrestors with 2 screens, 148 mag, 9/15 solas.

Ski runs absolutely great. Never skips a beat, pops right off and will idle across the lake. Best running ski I have tuned from scratch and I'm proud of it.
These my old carbs?
 
Joined
Feb 19, 2013
Likes
4,087
Location
Chico California
your going rich(?) did you turn in the screws and see if RPM gains? my experience with good ported setups jetting numbers are leaner than 80/135 because of the increased efficiency (draw or velocity) of the system. Tune on peak RPM

Example: Same motor
58 mph with 38's could be 70/130
58 mph with 48's could be 140/140

48's will get you their faster but require more jet because of intake velocity.
Forgot the tach, gps and gopro..
I had a bad one way valve. Replaced it and opened up the screws half turn each. Maybe a slight difference in 3/4-full now. For top speed, I was at the bouys working on my 180 stabs and two sparks took off in a race with the riders fully tucked. By the time I turned around they had about a 200ft head start. I ended up catching and passing them both. :)
 
Joined
Feb 4, 2016
Likes
1
Location
Michigan
Ran ok with old jetting, rebuilt carb and updated jetting try to help... the setup is below still struggling

Square Nose

Brand = Mikuni
Model = Retail
Size = 44
Quantity = 1
Main = 115 to 120
Pilot = 155 to 150
Needle/Seat = 2.0 before and after
Spring = black/dark to 95g
Pilot Screw = 1.125 to ___ . Been 1 to 3.5 will no better nor worse
Main Screw = 1 to ____. Trying to dial the pilot first.
Pop Off = was ____ to now 20psi. did not check before rebuild.
Arrestor: none previously (owner never ran one) to now tau ceti tornado with jacket
-----

Gas Octance = 93
Altitude =sea level
Main Riding = rec level, local lakes
WOT test = probably pass but havent tried
Powerband = standard - no porting
Motor type/setup: 701 61X cyl and cases, wet jet intake, boysen fiberglass reeds, 10/18 scat trak prop, factory b pipe (screws unknown-left from previous owner), stock yami cdi, 2" tau ceti arrestor

Idles perfect. Brought low speed out from 1 to 3.5 with slight improvement but still not crisp. Plugs were light brown/grey (leaner side-imo) but increased in pilot size from rebuild so confused as to why its still not boggy... im attempting to go way rich and dial back the pilot. Thoughts?

Added an additional gasket to the carb on the rebuild blue #2 in the pic. wondering if that could be giving me issues. It did not come out of the carb but the picture showed it so I put it in...? Could a flipped check valve disc be giving me these tunning issues?
Mikuni Carb Rebuild Question.jpg
 
Joined
Feb 4, 2016
Likes
1
Location
Michigan
@Cody Sampson Try 125Pilot jet and 150 Main jet with 24PSI pop off.
went to a 21 PSI popoff and ended up with a 130 Pilot Jet and a 160 Main jet.. 2 turns out on both screws. Seems excessive but the ski hasnt had the rich bog yet. Ran fine yesterday afternoon. Could there be an air leak causing the large jet sizes or do some engines just love fuel?
 
Joined
Apr 19, 2009
Likes
4
Location
canada
Need Help
2 x 44mm
760cc bore 85mm
porting cases and cylinders more a 6mm crankshaft,
Stock ignition with MSD Enhancer
do you have a starting jetting to advise me
Thank
 

Roseand

Ready to RIP
Site Supporter
Joined
Dec 31, 2012
Likes
2,002
Location
Wisconsin
Carbs off of an Oem 760 or retail sbns? Basically are there 3 or 4 transition holes in the throat of the carb?
I run Oem 760s 44s with a 5mil stroker 84mm bore/ported 760 cylinder and cases and 117.5 pilot and 122.5 main is the recommended jetting.

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