Super Jet Jetting and setup for Nynja C4 chamber

[BRANDO6X]

Hey there,

I am about to put my superjet back together and I was wondering if anyone had any insight on the carb and pipe settings that are needed to make a C4 chamber run well.

I cannot seem to find too much info from people that are running them, I hope someone with a similar setup to mine could post what they are running.

Current setup:

-61x/61x
-718cc
-cylinders and cases ported by me. Exhaust porting done with yamanube's template, and I did mild work with the transfers and boost.
-82mm Pro-x pistons
-ADA head with 35cc domes (not sure what the comp will be, I need to increase my squish first)
-Flywheel with Zero full lightening
-Boysen pro 35 reeds
-Single 44
-Intake mani is matched and widened
-Nynja Ex manifold and Head pipe, both matched and widened
-Nynja C4 chamber
-RN waterbox
-MSD enhancer
-9/15 hooker
-SN with 4in off the back

Any help would be greatly appreciated

 

[Roseand]

Seems like people wind up around 150 main and 125 pilot with 20-25 psi popoff for ported b piped skis, and I suppose the ninja might be similar. I personally would start rich to make sure. For example, most people run 150 ish mains but I'm at a 157.5.. Start rich and lean in!

Suggestion for tuning high speed: your main jet should be large enough that with the high speed screw at 2.5 turns out makes the ski gurgle at WOT. Turn it in until it revs clean, and then use a tach to find peak rpms and set your high speed approx 50-100 rpm rich of peak just to be safe. Remember, if you make a change to your pilot or popoff it affects the whole entire circuit. You can't just turn off the pilot jet, it adds to the total amount of fuel at WOT too. Maybe you know all of this, but just thought I'd give you a couple pointers so you don't wind up sticking a piston learning the hard way!

 

[Roseand]

Your squish should be no less than 40 thousandths and no greater than 50 or 55 otherwise you'll lose performance. Mine is at 48 thou with 35 cc domes at 180ish compression and I run WOT with pump 93 with no deto.

 

[BRANDO6X]

Ya it is currently at 20 tho, I was expecting to be a bit close because I had it decked but I was hoping for more like 35-40... not 20.. I think at max rpm there would be some metal to metal contact..

I am going to machine them to get between 35 and 40 tho, have you heard that going bellow 40 tho can be problematic?

 

[Roseand]

I wouldn't recommend it. Aim for 45 from what I hear...

 

[BRANDO6X]

Thanks for the response Roseland, Ya its seems that 150 main and 120-125 pilot are used quite often for my set up with a b-pipe, I am concerned about the difference with the C4 chamber. I have heard it produces a higher trapping pressure than a b-pipe, and has different water needs.

Ya def want to start rich and work my way back, what needle & seat do people use?

Can anybody with a C4 chamber comment on jetting and water settings they have found to work?

 

[Roseand]

I like a 2.0 n/s now. Seems like a lot of people do as well!

 

[Big Kahuna]

Roseand, Do you have a C4 Chamber? if not, How can you give recommendations?

 

[Roseand]

I gave general advice. 2.0 n/s works for nearly every set up since you can just swap out Springs.. Just trying to help. Never said I was an expert, so get off my tail.