750 with single carb

[JetskiMontana]

Need some advise from someone who has had a rippen 750 supplied from a single carberateur. I have a SBN 44 right now but couldn't get it to run just right. I can't recall what my high and lows are. But I tried adjusting the high and low set screws in and out with little improvement. Don't know if I should buy a bigger carb or just new jets. I would like to stay with a single carb for easier tuning so I don't have to mess around with 2 carbs. Thanks for any info!

 

[KMN]

How do the plugs look? Try changing them?

 

[JetskiMontana]

The plugs are brand new. I bought the motor from a guy about a month and a half ago. Since it was out and there was some questionable wear lines I had the cylinders bored .5mm to clean them up and bought the matching pistons. I tore the motor completely apart and changed every gasket to new with 1211 sealant to make sure there wouldn't be any air leaks. So the motor is fresh. I know it's a issue on the intake side as far as air to fuel ratio settings.

 

[Vumad]

My buddy has a X2 with a 750 SP, SBN44, I think the pipe is a 650PJS and a 12/18 straight bladed prop. It's tuned pretty well. Of course, a pipe is a major part of the tuning and you most likely have a different pipe. Anyway, here are the last tuning specs I have written down...

Main 125
Pilot 115
Needle 2.3
Spring 80
Pop off 14

 

[JetskiMontana]

Thanks for the info!

 

[Fenix169motox]

Hey I'm having similar problems as you Montana, my buddy has a rippin 750sxi with a sbn44 his jets are
Low 145
High 140
needle 2.5
Pop off 25

I did the same setup on my 750 sx motor (sbn 44. R&d intake, factory limited pipe) and I don't reach full rpm.
I'm watching this thread if I find something helpful I'll let you know dude.

 

[WB1994]

You should be around 120 pilot, 145-150 main. Dont reverse jet it. 2.0 N/S with 20 -25 popoff if your using a prok style arrestor.

 

[Fenix169motox]

You should be around 120 pilot, 145-150 main. Dont reverse jet it. 2.0 N/S with 20 -25 popoff if your using a prok style arrestor.

I can't get mine to reach full rpm
I bought a tinytach to get some numbers but I can hear it not rev as high as the other pro
Used to have a 115 pilot and 160 main and I had the same issue.
Right now since I haven't tried it I'm gonna see about the 115 / 125 the x2 guy has.
What's your significance of using a smaller needle valve? I went with the 2.5 because I was running out of fuel at w.o.t. my Pop off is set at 18 it's snappy but does not reach full rpm.

 

[Vumad]

I can't get mine to reach full rpm
I bought a tinytach to get some numbers but I can hear it not rev as high as the other pro
Used to have a 115 pilot and 160 main and I had the same issue.
Right now since I haven't tried it I'm gonna see about the 115 / 125 the x2 guy has.
What's your significance of using a smaller needle valve? I went with the 2.5 because I was running out of fuel at w.o.t. my Pop off is set at 18 it's snappy but does not reach full rpm.

Sounds like youre just throwing darts at a board. No reason to go from a 160 main to a 125 main just because its working for someone else. Thats a x2 with a 650 pipe and waterbox which are much more restrictive than what you couod have with your sxi.

Also if you had 160 mains you were probably too rich at wot, not too lean. A 2.3 seat woukd probably get you the popoff you need with less leakage. A 1.5 seat withh flow all the fuel your carb can use so you should only be going to bigger seats for a specific popoff number.

Also your popoff has nothing to do with wot so it cant be making you rich or lean.

You shouod spend some quality time with the mikuni manual and your carbs.

You could also have other issues affecting your rpm, like too much prop, a diferent sound that makes you think you have less rpm but really you just need a tach, a stock or damaged pipe that wont allow the same rpm your friends have (650 pipes are more restrictive, my 750 pipe had a damaged injection screw) etc that you may need to assess

 

[WB1994]

It says in the mikuni bible that the smallest N/S will flow more fuel than needed. It also says to use the smallest N/S while obtaining the required popoff. If your running out of fuel on the top with a 160 then somethings wrong. Its not your N/S. Im running a 150 main in a 771 big bore yamaha with a powerfactor pipe. Go to the Factory Pipe website and look at what they recomend for jetting when installing the B pipe. Thats exactly where you should be.

 

[Fenix169motox]

The only reason I went to the 2.5 is because during wot It would accelerate then hesitate, accelerate then hesitate forever
Changed that needle and seat then I had enough flow
Changed jet from 160 (which was in the Carb when I got it) to 145. It's almost the same machine
Pretty much yeah I'm throwing darts on a wall but so far none of my main jet changes have done anything to performance.

Sounds like youre just throwing darts at a board. No reason to go from a 160 main to a 125 main just because its working for someone else. Thats a x2 with a 650 pipe and waterbox which are much more restrictive than what you couod have with your sxi.

Also if you had 160 mains you were probably too rich at wot, not too lean. A 2.3 seat woukd probably get you the popoff you need with less leakage. A 1.5 seat withh flow all the fuel your carb can use so you should only be going to bigger seats for a specific popoff number.

Also your popoff has nothing to do with wot so it cant be making you rich or lean.

You shouod spend some quality time with the mikuni manual and your carbs.

You could also have other issues affecting your rpm, like too much prop, a diferent sound that makes you think you have less rpm but really you just need a tach, a stock or damaged pipe that wont allow the same rpm your friends have (650 pipes are more restrictive, my 750 pipe had a damaged injection screw) etc that you may need to assess

 

[Fenix169motox]

It says in the mikuni bible that the smallest N/S will flow more fuel than needed. It also says to use the smallest N/S while obtaining the required popoff. If your running out of fuel on the top with a 160 then somethings wrong. Its not your N/S. Im running a 150 main in a 771 big bore yamaha with a powerfactor pipe. Go to the Factory Pipe website and look at what they recomend for jetting when installing the B pipe. Thats exactly where you should be.

It says that I read it over and over, but my 160 jet is a larger hole than the 1.5 needle and seat are.
Now with the 2.5 I at least can operate at wot and not surge

 

[WB1994]

Also if you cant get it to run right with the balpark jetting i gave you then try a different carb.

Also is your pump side of the carb leaking? You need to use a popoff guage and bring the preasure up to just before it pops off and if the carb doesnt hold a steady preasure spray some windex on the pump to make sure thats not leaking.

 

[WB1994]

It says that I read it over and over, but my 160 jet is a larger hole than the 1.5 needle and seat are.
Now with the 2.5 I at least can operate at wot and not surge

Your 160 is too big. Trust me. Something else is wrong. Snag your buddys carb off his perfectly running ski and try it on yours.

 

[WB1994]

Post a picture of your pluggs.

 

[Fenix169motox]

I know it's too big my plugs are black.
145 Like my buddy's carb and it's not black.

My pump side does not leak I use my pop off gauge often. I will try out that jetting. It's a little lean on low speed but I'll give it a try.

 

[WB1994]

Wetjet put out the Kraze, single 46 , high comp head, westcoast exhaust. From the factory it had a 1.5 N/S with a 107.5 pilot and 145 main. Thats on a couch that runs wot all day long with mindless retards behind the throttle. Thats a factory craft under warrantee. Your setup is almost the same.

 

[WB1994]

Before you get too frustrated understand that carbs can go bad. Ive had quite a few that were gutted for parts. I had a brand new 46 with about a months worth of ride time last year not work for the life of me this year. A different carb and all is good again.

 

[Fenix169motox]

I'll try anything that would help
What "Goes bad" in a carb body? It's a cast piece that has holes and passage ways drilled into it. You can replace all the moving components inside.

Thanks for all the input guys but I feel like I hijacked this thread lol

Before you get too frustrated understand that carbs can go bad. Ive had quite a few that were gutted for parts. I had a brand new 46 with about a months worth of ride time last year not work for the life of me this year. A different carb and all is good again.

 

[WB1994]

I'll try anything that would help
What "Goes bad" in a carb body? It's a cast piece that has holes and passage ways drilled into it. You can replace all the moving components inside.

Thanks for all the input guys but I feel like I hijacked this thread lol

I wish i knew but i have a carb thats been old faithfull for me for fifteen or so years. An old school taper bored 61x carb. If me or someone i know has an issue out comes this carb to rule out if its a carb issue. I also can pull all moving parts out of this carb and put it in the troubled carb to help rule out what the issue in the carb is and ive had carbs not work with all the moving parts swapped into the other carb as well as the whole pump side of the carb. I have no clue why but it happens. Even chem dipping and compressed air doesnt work at times.