I find this to be true. If the rider is slower with throttle inputs the popoff can be raise a lot more than you may expect. All SBN44s have no problem opening a 115 spring, even on single carb 650s.
Carb Theory & Practice
- Thread starter E350
- Start date
- Location
- Charlotte, NC
i have found 25psi popoff with a 2.0 n/s 95g spring to be the sweet spot at least for me on popoff. this is with 44s or 46s and using a 61x style flame arrestor with 1 screen. then ill adjust jetting accordingly. at 25psi, i can get excellent throttle response and no fuel dribble. i prefer to use the 61x style flame arrestors over open filters especially on an engine that sees saltwater. i dont like replacing crankshafts every few seasons due to water ingestion. the 61x style flame arrestors are a good compremise between decent air flow and keeping water out of the engine.
waxhead
wannabe backflipper
- Location
- gold coast
Yeah its close to what I run. Heck my gauge may be out as well, But around the 20-25 range will get you into the sweet spot
sjetrider
615 Freeriders are addicted to T1 madness.
- Location
- in the 615 (Nashville)
115 and 2.0 should be way higher than that
I’m 2.0 with 95g and at 25psi
Maybe your springs were mid labeled
I’m 2.0 with 95g and at 25psi
Maybe your springs were mid labeled
Flash-FX
No Square..No Round..FX-1
- Location
- South Jersey Shore
Pop off and the dead horse...
And let's not forget about the IDLE MIXTURE SCREW! It's name says it all. It's for adjusting the IDLE MIXTURE. It's simple. Along with the idle speed stop, it's the first thing you should tune. If your ski has the wrong size pilot (L/S) jet and your pop-off is far from optimum, you should still be able to get it to start and idle perfect (ski tied to the trailer in the water). It's then when you start to open the throttle, you'll realize what direction you need to go. That's exactly when the pop-off show's up. If it's rich it blubbers a little. If it falls on it's face and stalls, it's lean. If it's lean (at this point) the idle screw can be opened a little to confirm the motor needs a little more fuel early and the pop off needs to be lowered (that's JUST A TEST. Set it back after confirmation). Go lower the pop off and retest. As the throttle blade is opened a little more, the pilot jet starts to show up. The carb is just running off the fuel coming out of those little drilled holes. Idle to low speed transition. Once the carb starts into low speed, the pop off is done doing it's thing and the pilot takes over. All this stuff is to try to create a linear fuel delivery, somewhat like fuel injection. But in a old school fashion.
Some tuning things to remember...
-The Idle mixture screw just handles the idle mixture (butterfly almost closed against the idle screw stop).
-DON'T use the idle screw to fix a high pop off (low speed response). Your plugs will become dark because every time you let off the throttle and the butterfly closes, the overly opened idle screw will be letting in too much extra fuel. Fiddling with the idle screw to mask another problem just fouls plugs. Later in testing, you could have a critically small main jet(s) that will squeak some pistons, and going by "plug readings" would indicate rich. You just got misled by a idle mixture screw. Be careful...dead horse ahead.
-If yous ski is over propped (too steep of a pitch), It will be extra difficult if not impossible to tune out the hesitation or BOG in the bottom end punch. The correct pitch let's the motor rev quickly through this delicate tuning area and get to where there's more power "on the pipe". Just 1* can make a major difference. Is your ski OVER PROPPED??
-Carb tuning is another reason this hobby is dying. Put the cell phone down and learn something old...
And let's not forget about the IDLE MIXTURE SCREW! It's name says it all. It's for adjusting the IDLE MIXTURE. It's simple. Along with the idle speed stop, it's the first thing you should tune. If your ski has the wrong size pilot (L/S) jet and your pop-off is far from optimum, you should still be able to get it to start and idle perfect (ski tied to the trailer in the water). It's then when you start to open the throttle, you'll realize what direction you need to go. That's exactly when the pop-off show's up. If it's rich it blubbers a little. If it falls on it's face and stalls, it's lean. If it's lean (at this point) the idle screw can be opened a little to confirm the motor needs a little more fuel early and the pop off needs to be lowered (that's JUST A TEST. Set it back after confirmation). Go lower the pop off and retest. As the throttle blade is opened a little more, the pilot jet starts to show up. The carb is just running off the fuel coming out of those little drilled holes. Idle to low speed transition. Once the carb starts into low speed, the pop off is done doing it's thing and the pilot takes over. All this stuff is to try to create a linear fuel delivery, somewhat like fuel injection. But in a old school fashion.
Some tuning things to remember...
-The Idle mixture screw just handles the idle mixture (butterfly almost closed against the idle screw stop).
-DON'T use the idle screw to fix a high pop off (low speed response). Your plugs will become dark because every time you let off the throttle and the butterfly closes, the overly opened idle screw will be letting in too much extra fuel. Fiddling with the idle screw to mask another problem just fouls plugs. Later in testing, you could have a critically small main jet(s) that will squeak some pistons, and going by "plug readings" would indicate rich. You just got misled by a idle mixture screw. Be careful...dead horse ahead.
-If yous ski is over propped (too steep of a pitch), It will be extra difficult if not impossible to tune out the hesitation or BOG in the bottom end punch. The correct pitch let's the motor rev quickly through this delicate tuning area and get to where there's more power "on the pipe". Just 1* can make a major difference. Is your ski OVER PROPPED??
-Carb tuning is another reason this hobby is dying. Put the cell phone down and learn something old...
waxhead
wannabe backflipper
- Location
- gold coast
That's brilliant. So well written
sjetrider
615 Freeriders are addicted to T1 madness.
- Location
- in the 615 (Nashville)
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
Although you can use the low speed screw to adjust mixture on the very bottom you really shouldn’t be using it for anything other than idle adjustments. Your pop off and low speed jet have a much larger impact at a throttle range above where the low speed adjuster does most of its magic. You can very easily be misled by the low speed adjuster when it comes to tuning pop off and low speed combinations. Assuming you’re using am arrestors I’d personally keep that pop off above 22-23 pounds and adjust my low speed jet to compensate from there. When I was first learning I was always having the classic “it bogs in the water but if you jump and stay on the throttle it pulls hard when it hits the water” issue and when I finally got over the “no way the pilot jet needs to be that fat” mindset I quickly realized just how wrong I was. Im not saying you’re going in the wrong direction, as I haven’t ridden your ski and just off bottom to one guy means one thing to another, but I am saying 105 pilot sounds insanely lean to me.
If you’re certain it got better going leaner and you don’t have any other issues going on then maybe keep going in the way that feels right.
You could also have a ton of fuel shaking out of the carbs at a low pop off and making it have the rich just off bottom feeling you are describing.
If you’re certain it got better going leaner and you don’t have any other issues going on then maybe keep going in the way that feels right.
You could also have a ton of fuel shaking out of the carbs at a low pop off and making it have the rich just off bottom feeling you are describing.
sjetrider
615 Freeriders are addicted to T1 madness.
- Location
- in the 615 (Nashville)
Been slammed lately, time to ride but no time to tune and test.
I am going to LOWER pop off this evening and test (just to ensure i am not lean between pilot jet and pop off).
I have literally been turning the low speed jet out to 1 turn to warm the ski, turning it in to 1/2 turn once in water (thats where it does best when riding) and then back out to 1 turn to blow out on trailer. It idles up when out of water but idles fine in water. Sounds lean on pilot RIGHT? But when in the water it has MUCH les bottom bog at 1/2 turn out.
My GF never notices the bottom bog and says ski runs great but idles up when side mounting sometimes. I notice ONLY when I drop into a setup wake letting all the way off throttle then hammering on it.
Maybe I am lean and it just feel like a rich bog? It is not a typical lean bog for sure, its a gurgle feel.
I will post results tomorrow.
currently 2.0 N/S and 95g spring 26 popoff, going to 80 spring to hopefully achieve 21 popoff and see what it does.
Keep in mind, I lowered the fuel PSI in these carbs by drilling the return and using a 75 return jet in return line. I will play with that today as well. Easy to swap jets in return line. But the fuel pressure is where most say it should be now (1.5 at idle around 5 at full rev on trailer).
I have been very spoiled running super similar setups for years that I knew the setups on. I feel like i am having to relearn how to tune (not that I ever considered myself good at it) I have just got it right on my own skis over time then stuck with what worked.
In all honesty, I have realized that running T/L for years has been a tuning crutch, I can get away with rich tuning WAY more than this 760 ZEEL that has what I believe is a weaker spark than a stock setup.
It doesn't overcome water ingestion for poop either.
I appreciate the feedback and will accept all constructive criticism too.
Bun Pipe install on hold until I get the smaller tank (hopefully this weekend). Running Thrust tanks in both skis and never realized hers is a 5gal and mine is a 4.5 which with a Bun pipe makes a HUGE difference, PFP fits both no problem.
I am going to LOWER pop off this evening and test (just to ensure i am not lean between pilot jet and pop off).
I have literally been turning the low speed jet out to 1 turn to warm the ski, turning it in to 1/2 turn once in water (thats where it does best when riding) and then back out to 1 turn to blow out on trailer. It idles up when out of water but idles fine in water. Sounds lean on pilot RIGHT? But when in the water it has MUCH les bottom bog at 1/2 turn out.
My GF never notices the bottom bog and says ski runs great but idles up when side mounting sometimes. I notice ONLY when I drop into a setup wake letting all the way off throttle then hammering on it.
Maybe I am lean and it just feel like a rich bog? It is not a typical lean bog for sure, its a gurgle feel.
I will post results tomorrow.
currently 2.0 N/S and 95g spring 26 popoff, going to 80 spring to hopefully achieve 21 popoff and see what it does.
Keep in mind, I lowered the fuel PSI in these carbs by drilling the return and using a 75 return jet in return line. I will play with that today as well. Easy to swap jets in return line. But the fuel pressure is where most say it should be now (1.5 at idle around 5 at full rev on trailer).
I have been very spoiled running super similar setups for years that I knew the setups on. I feel like i am having to relearn how to tune (not that I ever considered myself good at it) I have just got it right on my own skis over time then stuck with what worked.
In all honesty, I have realized that running T/L for years has been a tuning crutch, I can get away with rich tuning WAY more than this 760 ZEEL that has what I believe is a weaker spark than a stock setup.
It doesn't overcome water ingestion for poop either.
I appreciate the feedback and will accept all constructive criticism too.
Bun Pipe install on hold until I get the smaller tank (hopefully this weekend). Running Thrust tanks in both skis and never realized hers is a 5gal and mine is a 4.5 which with a Bun pipe makes a HUGE difference, PFP fits both no problem.
Quinc
Buy a Superjet
- Location
- California
that sounds like your main jet is rich to me. If you hammer the throttle to half throttle how does it feel vs full throttle?
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
Flash-FX
No Square..No Round..FX-1
- Location
- South Jersey Shore
I think what Mikuni is referring to is that a condition can exist with stock style (high restriction) "air filters" and lower pop offs. It's like pulling the choke on throttle off deceleration. Too large of a carburetor(s) on a motor would do that. You end up tuning yourself in to a corner. Properly sized carbs for a motor application is what everyone needs. They provide a stronger signal that you can tune (providing the rest of your setup is on the same page, no goofy stuff).
waxhead
wannabe backflipper
- Location
- gold coast
Thats awesome and so true
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
I guess my real question for you guys is where do you draw the line on too big a carb.
What do you guys use to determine when a carb setup is too big for the engine it’s bolted to?
sjetrider
615 Freeriders are addicted to T1 madness.
- Location
- in the 615 (Nashville)
Yeah, thats been an issue in past, but not with these carbs as of yet. However, I went out at lunch and dropped the popoff (didnt have 2 80g springs that would pop the same, so put in 65g springs) so i am popping at 18 down from 26psi, big jump. When revving now, I DO have some dribble in rear carb. A problem for another day LOL. It idles way smoother but I cannot get the low speed to increase the idle
When doing the standard jetting test. 1/4 throttle, let off, hammer. No issues and Full Throttle, let off, Hammer it, NO ISSUES.
The issue ONLY shows when at low throttle or blipping throttle, letting completely off (dropping into s setup wake) and then hammering throttle.
Update:
The gas tank showed yesterday afternoon so I decided to install the Bun pipe rather than go test the new popoff setting yesterday.
So this evening I will be testing the Bun and new popoff combo (I know, one change at a time), but I couldn't resist , I think the Bun will be better suited for this 701 setup than the PFP as it gives a little more on bottom end and water can be adjusted via jets to tune throughout.
I was on the verge of adding water injection to the PFP before finding a Bun reasonably priced.
- Location
- Charlotte, NC
I bet you could put the 95g spring back in and change the 75 jet in the return for a 80 or 85 jet and it will smooth out for you. The jetting and popoff also affects the fuel pressure as well. Just going from a 70 to 80 return jet made a tremendous difference on my engine..
sjetrider
615 Freeriders are addicted to T1 madness.
- Location
- in the 615 (Nashville)
I can try that. I started with 26 popoff and a 60 return jet, Tried the 75 jet and it was better, I did try a 100 return and it seemed to flatten out the power although idles better. Went back to the 75 jet. I need to order more jets, I can pull an 80 out of my Bun pipe stinger and try it while testing tonight but I am going to try the 18 popoff with 75 return first.
The 18 popoff idles well and throttle response from idle is good on trailer but we will see once its under load.
I feel like the prop may still be a little tall for bottom end response too. Hoping the bottom end increase from the Bun (wet pipe) overcomes it some.
I have some main jets and 80g springs coming and will definitely try some other scenarios.
Right now the idea that I could be lean between pilot and popoff (although it feels rich except at idle out of water) is the theory I am targeting.
I have to be awfully desperate before I run a boring bar down the throat of a standard SBN46.
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
I’m not saying all aftermarket carbs are made equal but there are a few brands out there that will eat a sbn46 setup alive.
But you didn’t answer my question Kevbo, where do you personally draw the line? I will attest from personal experience that a set of 50mm FS’s hit and pull harder on my 760 than a set of 48’s and a set of 46’s wouldn’t even be close. Would I put them on a stock 650/701? No. Would I put 48mm duals on a ported 701 with decent bolt ons ? Absolutely, if it was in budget.
Ain’t nothing wrong with 44’s/46’s and they make good power but I’d say night and day comparatively to a set of 48’s and up on most setups.