Jetting, help me please...

Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
Ok I'm hoping someone on here is a guru with jetting on superjets... I cannot for the life of me get mine dialed in. Anyone got any ideas for baseline jetting on my setup? Looking for a better starting point cause clearly what I have no is not working, very rough idle, good low end power, crap midrange and top end.

My setup: 760cc 61x top end, 62t cases, both heavily ported, 190-195psi Ada girdled head, msd ignition, stator advanced 2 degrees, vforce 3 reeds, dual OEM 44's,1.5" hot products FAs with blowsion raincoats, choke delete, added primer, b pipe (manifold ported to 52mm I believe), tnt waterbox, dual cooling, lightweight flywheel and couplers, 08 sj impeller.

Sent from my HTC One_M8 using Tapatalk
 
Last edited:
Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
I'll get those in the morning, I built up the carbs back in January and forgot to write down the settings. All I know at this point is 2.0N/S and 95g Springs.

Sent from my HTC One_M8 using Tapatalk
 
Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
Ok so I forgot I could just check my jet kit to see what's missing. I'm currently running 112.5 pilots, and 137.5 mains, 2.0ns with 95g Springs. I'll check pop off in the morning. I believe I had it to around 20psi at 80g Springs I'd I recall correctly. Also both carbs have a fresh rebuild kit and we're sonic cleaned last year before I put it away.

Sent from my HTC One_M8 using Tapatalk
 
eastcoastjumper

eastcoastjumper

James
Site Supporter
Location
Long Island
Parsonsjb88 said:
Ok so I forgot I could just check my jet kit to see what's missing. I'm currently running 112.5 pilots, and 137.5 mains, 2.0ns with 95g Springs. I'll check pop off in the morning. I believe I had it to around 20psi at 80g Springs I'd I recall correctly. Also both carbs have a fresh rebuild kit and we're sonic cleaned last year before I put it away.

Sent from my HTC One_M8 using Tapatalk
Click to expand...

You'll have around 25-28 psi pop off with a fresh 2.0 ns and 95g springs. i use multiple springs of the same size to get the closest match and then play with the arm a little to get them even.

Important to get the carbs dead even with repeated trials. You can also use a motorcycle style carb vacuum gauge to get the throttle valves sync'd

I could give you jetting for 38's for this setup, but i have never played with 44's on it. good luck!
 
Harbor

Harbor

Location
Stockton
Have a mostly similar set up as yours I jetted, only its a bigger engine and a stroker, and has the aftermarket 44 mikuni 4 transfer hole carbs. I used 100L, 125h, 2.0 seat, 65 gram spring, about 14 pop off, 1 turn out each at sea level, runs very well..

Note, this boat is not running wide open for longer then 3 seconds
 
Sasquachcrap

Sasquachcrap

Location
North Carolina
I am running 61x ported cylinder with 62t bottom. 200 psi. Vf3 reeds. Total loss with lots of timing in the bottom and a power factor pipe dry. My carbs are stock 44s with the chokes removed and I'm running pod filters. I would start with 20-25 pop off and 115l and 130 high. This is in a chan and it's hard to run it wide open long. But it pulls super hard and I feel like it's set up well. Since the hot weather has gotten here I have had to lean out the screws just a tick because the boat developed a grumble off idle.
 
Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
Thanks for everyones replies. Maybe I'll try 120 pilots with 135 mains tomorrow. Today was a fail. With how rough the engine idles I'm wondering if there is something wrong with 1 of my carbs. Getting to the point where I'm about ready to cave and buy some blackjack carbs. So demotivating when you put in this much work building a custom ski and you can't even get the engine running.

Sent from my HTC One_M8 using Tapatalk
 
Sasquachcrap

Sasquachcrap

Location
North Carolina
I have been in your shoes when I started tuning my Superjet. Start with 115 135. I bet you end up with 125s or 130 on top. Be sure to check your carb baskets and be sure the returns are clear. If there is an engine issue blackjacks won't fix it. I wouldn't spend money until I knew the problem was carbs.
 
V

Vortex

Location
Southeast
The low end circuits are key. Simple test turn your low speed screw out 2-3 turns, see if it idles better. Then jet up until you reach about a 1.5 turn sweet spot on the low screw and it starts with the touch of the button with no trouble


Pop off will be close when it revs at the slightest opening of the throttle.

3/8 throttle and up is all main jet size. Wot is the hi screw, shoot for a jet size that gives you a clean wot at 1 turn or less.

Also...have you checked your coil? Bad coils/wires can act very finicky, are the plugs wet?
 
Last edited:
Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
Most my testing as been at home hooked up to the hose to keep the engine cool so I'm really just trying to get it to idle and Rev a little into the midrange before I go out to the water. Plugs are always wet. But soon as I screw the mixture screws in even the slightest it won't idle and I have to prime it to get it to start. The inside of the engine and exhaust is coated with a thick coating of black oily sludge. Also it was vibrating so bad and the midshaft was so hot I couldn't touch it so I pulled the midshaft and installed the motor by itself to ensure the vibration wasnt alignment related, made no difference. And I still have a horrible rattle from what seems like the flywheel area, I just can't narrow it down since I can't get it to idle right.

Sent from my HTC One_M8 using Tapatalk
 
Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
I'm not wanting to tune it out of water, I just want it to idle even remotely OK. I have nowhere that I can tie off at a dock and test for hours on end. Everywhere is a public launch that is too busy to do that at. :(

Sent from my HTC One_M8 using Tapatalk
 
Last edited:
Parsonsjb88

Parsonsjb88

Location
Windsor, Ontario
Would worn splines on my driveshaft cause a rattling or weird noise? I thought my midshaft bearings were prematurely shot for some reason but the bearings are still tight with no wobble, however I can rotate the midshaft to driveshaft has probably about 3 degrees or so of play when I spin it clockwise and counterclockwise repeatedly.

Sent from my HTC One_M8 using Tapatalk
 
You must log in or register to reply here.
Top Bottom