Opinion for jetting

K

Keith Ivey

Location
California
I have a 1993 superjet with a 701. I am looking for opinions on what my jetting should be. Here is a breakdown of the engine. It was a 701 but has pistons that are 75 over. It has a DASA head running about 175 PSI on compression. It has a lightened flywheel. Porting was done but I don't know by who or the specs. Factory B pipe. Electronics were modified to increase rev limiter. The carburetor is currently a 46mm with a main 150, pilot 120, seat and needle 2.5, and an 80 gram spring. I have the low set at 2 turns out and the high at 1.5. When i am about half throttle and go to give it full throttle, it delays about 2 seconds and then kicks in.
any recommendations would be appreciated. I think i need to increase my pilot jet????
 
kevbo

kevbo

Location
dfw
More importantly, what RPM is it turning? If the exhaust port is low then it needs to spin at least 6800. If the port is high make it turn 7000. The main jet and top screw need to be slightly rich of peak rpm at full throttle. If this doesn't register then you are just throwing darts.
 
DylanS

DylanS

Gorilla Smasher
Location
Lebanon Pa
Keith Ivey said:
I have a 1993 superjet with a 701. I am looking for opinions on what my jetting should be. Here is a breakdown of the engine. It was a 701 but has pistons that are 75 over. It has a DASA head running about 175 PSI on compression. It has a lightened flywheel. Porting was done but I don't know by who or the specs. Factory B pipe. Electronics were modified to increase rev limiter. The carburetor is currently a 46mm with a main 150, pilot 120, seat and needle 2.5, and an 80 gram spring. I have the low set at 2 turns out and the high at 1.5. When i am about half throttle and go to give it full throttle, it delays about 2 seconds and then kicks in.
any recommendations would be appreciated. I think i need to increase my pilot jet????
Click to expand...
If you can describe what you’re feeling at what throttle position better it will be a lot easier for someone to steer you in the right direction.
Sounds like the delay is a major rich condition starting at 1/2 throttle or so that clears up at WOT?
Here is a excerpt from the super BN guide, it’s full of great info, read the last paragraph
Personally I recommend making only one change at a time so you’re certain you know what did what.
 

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K

Keith Ivey

Location
California
It is at about 3/8 to 1/2 throttle when go to punch it it delays about 2 seconds. But also, once it does get to f
DylanS said:
If you can describe what you’re feeling at what throttle position better it will be a lot easier for someone to steer you in the right direction.
Sounds like the delay is a major rich condition starting at 1/2 throttle or so that clears up at WOT?
Here is a excerpt from the super BN guide, it’s full of great info, read the last paragraph
Personally I recommend making only one change at a time so you’re certain you know what did what.
Click to expand...
It is at about 3/8 to 1/2 throttle when I go to punch it, it delays about 1.5 to 2 seconds. But also, once it gets to full throttle, after about 6 seconds it dies. and what does WOT mean?
 
DylanS

DylanS

Gorilla Smasher
Location
Lebanon Pa
Keith Ivey said:
It is at about 3/8 to 1/2 throttle when go to punch it it delays about 2 seconds. But also, once it does get to f

It is at about 3/8 to 1/2 throttle when I go to punch it, it delays about 1.5 to 2 seconds. But also, once it gets to full throttle, after about 6 seconds it dies. and what does WOT mean?
Click to expand...
When you have this “delay” does the motor sound like it’s about to shut off momentarily? Or does it sound like it’s sputtering then gradually climb in rpm?

You need to be able to differentiate between a lean hesitation and rich stumble.
If your motor is shutting off at full throttle (WOT = wide open throttle) you are very lean.
Try Turning your high speed screw out to see if your wide open condition gets better.

Have you measured pop off pressure with a gauge? What air cleaner are you using. 2.5 with 80g should be close to 14psi
 
Last edited:
K

Keith Ivey

Location
California
DylanS said:
When you have this “delay” does the motor sound like it’s about to shut off momentarily? Or does it sound like it’s sputtering then gradually climb in rpm?

You need to be able to differentiate between a lean hesitation and rich stumble.
If your motor is shutting off at full throttle (WOT = wide open throttle) you are very lean.
Try Turning your high speed screw out to see if your wide open condition gets better.

Have you measured pop off pressure with a gauge? What air cleaner are you using. 2.5 with 80g should be close to 14psi
Click to expand...
it does not sound like it is going to shut off. it does not sputter either. Say i was 3/8 throttle, running great and then i WOT, it still runs smooth until at the same RPM and then it just kicks in and goes. As far as the WOT condition, we were able to correct that by opening up the high speed adjuster like you suggested but the other problem remains.
 
K

Keith Ivey

Location
California
Keith Ivey said:
it does not sound like it is going to shut off. it does not sputter either. Say i was 3/8 throttle, running great and then i WOT, it still runs smooth until at the same RPM and then it just kicks in and goes. As far as the WOT condition, we were able to correct that by opening up the high speed adjuster like you suggested but the other problem remains.
Click to expand...
I'm no expert but from the research that i have done it sounds like the pop off pressure may be to high. Thats what it feels like. It feels like something just opens and the engine is getting the fuel it needs.
 
DylanS

DylanS

Gorilla Smasher
Location
Lebanon Pa
Keith Ivey said:
it does not sound like it is going to shut off. it does not sputter either. Say i was 3/8 throttle, running great and then i WOT, it still runs smooth until at the same RPM and then it just kicks in and goes. As far as the WOT condition, we were able to correct that by opening up the high speed adjuster like you suggested but the other problem remains.
Click to expand...
Glad you got one issue sorted out!
if you post a video of it I’m 99% sure I can tell you if you’re experiencing a lean or rich condition.
Either way 3/8th throttle is where the high speed jet takes over for the low speed. Try bumping up 5 points on the low speed to rule out a lean condtion caused by a undersized low speed jet. If that doesn’t do it, go down 5. If no difference try the same with the high speed.
 
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