Super Jet Help! Installed Factory B Pipe - falls flat on face.

Jeru

Jeru

Location
Sacramento
Hey guys, I finally got my hands on a Factory B Pipe exhaust, and Man does it rip! I had a question for you all since the answers out there are pretty vague.

After installing the pipe the mid range is non existant. it'll have a good low end response and top end is crazy good. But getting it out of 5 mph mode is a challenge. Usually i have to lay off the gas a few seconds to let water pressure subside , then a full zero to max throttle works just fine.

After researching on the forums, i guess its related to pop off pressure and jetting etc? I have a Blackjack buckshot 44 sbn carb with stock spring, needle, seat, and jets. I just ordered the low and high speed jets recommended in the Factory Pipe install guide. Also used their recommended carb low/high settings. I had the water screws on the pipe all the way in except the bottom is 3/4 turn out (recommended). Any other suggestions? Thanks fellas
 
Jeru

Jeru

Location
Sacramento
Looks like I have to wait until friday to get the new jets :cool: Thanks Little_Franny and tor*p*do sounds like great advice. Will post updates
 
just joe

just joe

Site Supporter
Location
NorCal
Check if it's lean. Ride at the slowest speed possible for at least 30 seconds then nail it. If it hesitates it's lean, if it takes off then stumbles it could be rich. Use the low speed needle before changing pop-off.

Also, I used to run bottom and middle screws closed, top open 5/8 - 3/4.
 
Roseand

Roseand

The Weaponizer
Site Supporter
Location
Wisconsin
BruceSki said:
Ask that pro tuner how he knows^^^^
Click to expand...
Sometimes you have to learn the hard way. I used the specs that most people use for ported 701s, and my ski felt fine. Tuned it on the trailer and called it good. 10 hours later I stuck it not even going WOT.

Since then I kept going up on my main until I could get it to gurgle at 2.5 turns out, and I turned it in till it got better. Then I tuned it for peak rpm and then richenened a quarter turn from peak. Needless to say, my ski runs great all around now and I run it WOT a decent amount. Plugs are great color after WOT runs too.
I started with 150 main and 125 pilot which I was told would be way too rich on the top end. I ended up with a 157.5 main, 127.5 pilot, and 25 psi popoff instead of the 34 I had before. The porting in my ski likes more fuel. Took about 6-7 rejets and popoff changes to get it where I wanted it, but it was worth it.
 
Jeru

Jeru

Location
Sacramento
Wow sounds like its science and physics 101 :) thanks for the education and suggestions for jetting specs you all have tried. Would it be worth investing in a pop off pressure gauge?
 
Roseand

Roseand

The Weaponizer
Site Supporter
Location
Wisconsin
Absafreekenlutely! There is too much of a variance between what the springs should read, and what they do. I've had a 80 g read 18 psi and then I put in a 95 g spring thinking I didn't need to check it. I wondered why my ski didn't feel any better... It was 20 psi instead of the 25 it should be! I cut down an old spring and got it to 25 psi and my ski was finally snappy again!
 
Jeru

Jeru

Location
Sacramento
Sorry to resurrect an old thread but I have finally had a moment to take the ski out and run some tests with the new jets. Lots of trial and error, hopefully it's getting closer.
Tried the following setups on the Black Jack 44mm:

Run #1
(previous Riva wet pipe worked fine on this jet/dull silver spring)
130 pilot jet
145 main jet
felt good on top end but was lacking in the idle to WOT. non-existent low to mid end.
Only way I could get the ski to do a full throttle was letting the ski go to idle then punching it hard and it would scream once it was pinned.

Run #2
(Dull silver spring)
120 pilot jet
150 main jet
top end got slightly worse but the bottom end was acceptable. Not super crisp and responsive but enough to get me down the lake a few passes. Finally the ski started to have the issue of low end no throttle response past 1/5 throttle unless I gunned it hard from a dead stop. Another thing to note this was right in the morning maybe 8AM so the air was pretty cold.

I do have the pilot sizes between 120 and 135 pilot and 142.5 to 157.5 main available.

Should I start moving up from my base run #2 one jet at a time? What psi should I be looking for pop off to be at? Silly of me to think I could do this with only jetting and not doing some pop-off work (equally silly was jumping 3 sizes on the pilot jet between runs :oops:)

Ride on! BRAP! ;)
 
Last edited:
Jeru

Jeru

Location
Sacramento
Heya JetManiac, if you could bear with me I'm pretty new at this as you can tell. Yes, last night I got to read the mikuni manual pdf and learned more about pop off and how it affects the low end fuel delivery . Now I have a handy chart showing spring and needle and seat combinations. Almost certain this is the issue.
 
motoman3000

motoman3000

ride
Site Supporter
Location
new jersey
Jeru said:
Heya JetManiac, if you could bear with me I'm pretty new at this as you can tell. Yes, last night I got to read the mikuni manual pdf and learned more about pop off and how it affects the low end fuel delivery . Now I have a handy chart showing spring and needle and seat combinations. Almost certain this is the issue.
Click to expand...
Ok now then get on it and report back and try to keep this under 50 pages !!

Edit- drinking now take my comments w/ a grain !
 
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