Sbn 44 and fpp jetting

[Fenix169motox]

This type of tread needs to be a sticky.
Compression 145/145
Stock engine
Sbn44.
Pilot jet 115
Main 175
Pop off 30
Fpp settings:
Bottom 1 turn.
Top 1/2 turn
Middle class.
I'm having trouble with throttle response. I followed my sbn tuning book so that's how I got my jets so big plugs are ashy black. Idles great for no wake zones.
But if I go from idle to full it hesitates, then rips then weak again. Here's the kicker. I get similar results when I have a 75 pilot jet and 135 main.
Do I need to be richer yet?

 

[heynagel]

Doubt it. 175 sounds crazy high. Most single 44 specs are around 150 H, 120 L. I would start with those numbers and work from there.


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[tor*p*do]

Doubt it. 175 sounds crazy high. Most single 44 specs are around 150 H, 120 L. I would start with those numbers and work from there.

120/150 is on a yami motor
750 is different application

 

[Fenix169motox]

So nobody here is using a single sbn 44 and a factory limited pipe?
I will go get 120 150 jets then.

 

[johnmx854]

I have a similar set up on my 750sxi pro and am also having similar issues.. I have a 155 main and 122.5 pilot and get hesitation off the bottom then rips pretty good after that.... I'm not positive on the size of my carb but was told to try 117.5 pilot and see what happens


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[Fenix169motox]

You went from duals to a single? I got rid of my hesitation from idle, but I had to adjust my pop off to 22 psi and my low adjuster is 3 turns out..
With a 115 pilot.

 

[johnmx854]

Yes I bought it with he single on it already but have the stock duels if I decided to switch back. I was told besides the single being easier to tune that it does provide better performance when being jetted properly... How is he pop off pressure adjusted? Is that the spring inside the carb that needs to be changed? I understand you need the gauge but wasn't sure how to adjust it.


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[Fenix169motox]

Yes I bought it with he single on it already but have the stock duels if I decided to switch back. I was told besides the single being easier to tune that it does provide better performance when being jetted properly... How is he pop off pressure adjusted? Is that the spring inside the carb that needs to be changed? I understand you need the gauge but wasn't sure how to adjust it.


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to adjust pop off you will need to either change the spring under the needle arm OR lightly bend the needle arm to fine tune. but you cant bend it far or you will either not get pop off or have pop off all the time (due to interference of diaphragm and carb body)
I had the stock duels on my pro and it was a million times faster than any of my single carb 750's
SO i installed the 120 low and the 160 high (couldnt get a 150 from anyone) and my plugs look good. but i still have a hesitation. i might need to adjust pop off a little lower. Waiting for my 13/18 supra then i should really notice a difference.

 

[Fenix169motox]

I would be interested in a duel setup for mine BUT i would need the 10 bolt manifold. and i really dont know how much i want to do to this small pin. might as well start searching for a big pin anyway.

 

[Fenix169motox]

SO i made a video of me riding, at the end i'm trying to show how there's a hesitation before it revs. idle. (pull throttle)......vrooom
you'll be able to hear my homemade waterbox. took some 6" irrigation tubing. made an 8" tall cylinder. i made the exit tube reach down into the cylinder so its about an inch off the bottom. so any exhaust gasses have to go under water before exiting.

 

[Magyar68]

I would be interested in a duel setup for mine BUT i would need the 10 bolt manifold. and i really dont know how much i want to do to this small pin. might as well start searching for a big pin anyway.

You can use the 12 bolt mani. I am using a 10 bolt mani on a Bigpin Stroker. If you go for Duels get the mikunis and Throttle wheel so you don't have to change your throttle cable, and bracket. then you can just drop in 150/75 or 80 call it a day.
Have you tried the 75 with the 175?

 

[Fenix169motox]

Making a throttle bracket wouldn't be to big of deal..
But yes 75 low and 175 main was 5 turns and 20 pop off and up top was too rich.
I'm currently running 120 low 35 pop off and 160 main and my plugs are golden brown.

 

[Magyar68]

you still have your response issue?

 

[Fenix169motox]

It's Not bad more. I'm more thinking that the water box I made isn't helping. And I think I need more impeller.