Need Jetting Help

[Shonuff]

I took the new SuperJet out today and noticed a terribly unpredictable bog at low speeds. It would, for the most part, idle acceptably and take off but the low range was bad and boggy.

I followed Group K's carb tuning guide and nothing changed. I ended up with both low speed screws set out a full turn from closed.

My top speed was incredible. It ran right with my SX-R but at 30 seconds of WOT, it would cut out as if it was no longer getting gas. I could restart it while fighting to keep it upright, feather the throttle a little, and take off again.

What jetting do I want to start with?

I've got dual 46mm Full Spectrums, b-pipe, tau ceti arrestors and 160 psi in each cylinder.

Thanks.

 

[Shonuff]

Little help?

 

[Idok]

ported.....unported?

 

[Idok]

ported.....unported?

just waitin' on you buddy...

 

[MrSki]

You can mess with the jets and pop-off to get it to run right at low speeds. I'm thinking you might have some other issue at top speed. It should not flat out and die on you even if you are hitting a rev limit.

 

[ANT]

You should be able to get rid of the top-end problem with the adjusters. On the low end turn out the adjusters and see if it gets any better, if it does then try to jet up your low speeds. If it doesnt do anything it could be your pop-off. If the pop-off isnt right, it can seem like a low speed jet problem. It's probably a combo of both though

 

[douglee25]

I wouldn't make WOT runs the way it is. If it shuts off after 30 seconds, you may be having a lean seizure.

Doug

 

[Shonuff]

I think I'm lean up top.

I'll try turning out the lower jets a little.

I don't think it's been ported but I don't know for sure.

If I were to order replacement jets, what would be a good set to start with?

Thanks.

 

[ANT]

Before you order them check and see if there is a shop around you that has a set of jets because you can just take your old jets there and they will trade you straight up for a new set of jets and buy a couple extra bigger sets from them and when you get it right bring em back and get your money back because jets are expensive for what they are. Order at least each size up to four sizes bigger than what you have in your ski already.

 

[Shonuff]

Unless they're named Harry or Paul, I don't trust them. :sneaky:

 

[Shonuff]

I'm going to call Ed Brazina tomorrow and ask him about what I have and possibly what I need.

 

[nikad58]

i hate to say this but. no one can help till you know what you have to ask them.. you could have a big bore ported or a stocker.. how can anyone help you ?? sounds like a fuel pump issue tho.. do a plug check on your low and top end along with a leak down test also.. your readings will tell you something..

 

[Shonuff]

Per my conversation with Ed:

1.8 Needle and Seat
95 gram spring for 25 pounds
120 to 122.5 Low Speed Jet (Pilot Jet)
135 High Speed (Main Jet)
#60 main jet to restrict fuel return in fuel return line
Low Speed Adjust Screw turned out one full turn
High Speed Adjust Screw turned out only one half turn

 

[Superjetjim]

My set up is similar:

Superjet
62T 701 bored to 753 with porting
Stock stroke
Factory B Mod
ADA Head @ 185PSI
MSD Enhancer

I'm at:

1.8 Needle and Seat
95 gram spring for 25 pounds (Dull Silver)
120 Low Speed Jet (Pilot Jet)
130 High Speed (Main Jet)
#60 main jet to restrict fuel return in fuel return line
Low Speed Adjust Screw turned out one 3/4 turn
High Speed Adjust Screw turned out only one half turn

Tried a 125 low speed jet first but it wasn't very clean so went to a 120 Low

A 130 Main jet will run well at Sea level (more fuel needed) but at elevation the 125 is probably closer to what you want.

.5 up or down (example 125 to 130) is equal to 1 x turn of the jetting screws - past 1 3/4 turns 'out' Full Specs won't meter properly so you need to move up a jet - same applied if you at less than 3/4 turn from closed - move down a jet.

Also make sure your fuel tank is air tight and your one way valve is working correctly - no tank pressure makes FS run like poo!

Good luck..

Jim

 

[Shonuff]

I think part of my problem is that I'm running with a shiny silver 65g spring currently. I have ordered two new spring sizes and a popoff gauge.