Super Jet which springs are these (mikuni kit)

[aramis]

Hi,

Tore into my carbs, and can't figure out what spring was in there. Please check out the pic and let me know if you can tell what it is. Pop-off tester won't be here for a few more days...

2 springs on left came in a genuine Mikuni SBN 38/44 rebuild kit (what are they?) and the 1 on the right is what was in my carbs. I'm thinking that the stock 115g was in there all along, instead of a 95g, due to the mistake on Factory Pipe's instructions...

Also, N&S were worn, and replacement 1.5's are on the way. With prok's, 180psi (35cc domes), EPIC cdi running waxhead's curve, b-pipe, stock 38's w/ 75/135, should I still be looking for a pop-off of about 45-50psi? Or, should I go a bit lower?

Thanks!

 

[SUPERTUNE]

The Mikuni kits come with a 65 gram spring (shinny silver) and 115 gram spring (used to be gold and now are chrome color)
I'm betting that for sure your spring is a 115 gram spring. An older one that the gold color is washed off over the years from the fuel.

 

[aramis]

Thanks Chuck, at least I have some reference point now. I searched the X and Google for over an hour trying to find out what springs came in the standard kit!

The spring that was in there was probably put in 8 years ago, so it was definitely an old style.

 

[2lick]

There is a real good post on here in the FAQ that tells you about springs and jets....

 

[aramis]

Yeah, I've read that post several times...but since none of my 3 springs were reverse wound or had a single wind on the ends, I couldn't figure out why I had 3 different length springs. That picture of the 4 mikuni springs is all well and good if you have all 4 springs to look at, or 1 known spring. You can then figure it out from there. My problem was that the original Mikuni kit I bought only came with 2 springs, and I didn't know what they were. I can now piece together the puzzle from there...

 

[Air time]

I have a SBT rebuild kit with 2 springs would that be the same as a genuine kit 65g and 115g in it,so is the smallest one on the left 65g??? cause they all look different type of silvers..

 

[Matt_E]

Original Mikuni springs are 65g shiny silver and 95g dull silver.
In recent years, the 115g springs are also silver.
Can't speak for non Mikuni stuff. I'd use a popoff gauge to verify.

 

[Air time]

Thanks matt any links or pics on how to do it with a guage?

 

[Crab]

I don't recall off the top which one, but one of the 4 is twisted opposite of the other 3 like you have, somewhere I have the pic.

 

[Matt_E]

Short version:
Attach the popoff gauge to the fuel inlet nipple and block the fuel outlet nipple.
Pump up the pressure until it releases. That release pressure is your popoff pressure.

Long version:
You should have the diaphragm cover off and the diaphragm removed. Put a very small amount of premixed fuel or WD40 in the seat area. This lubricates the needle tip and gives you a more accurate reading.

Bonus points:
As you pump up the pressure, be sure to look closely at the needle & seat from directly above to observe the popoff visually.

 

[Proformance1]

LOL, visually, and dont wear safety goggles while gazing directly into the needle and seat.

 

[Crab]

Use wd40 and cover with a paper towel for safety, not fuel.

 

[Matt_E]

FYI, WD40 is flammable, too. :biggrin:
Most anything in aerosol form is.

 

[jetpilot08]

So you shouldn't be using a lighter as a light source? :dunce:

 

[Crab]

FYI, WD40 is flammable, too. :biggrin:
Most anything in aerosol form is.

Yea but it tastes better by far.:Banane09:

 

[Matt_E]

Haha, for sure.
Actually, screw the WD40, I'm doing this with beer next time.
Crab brew...