Jetting Required for 300sx with Mariner pipe?

[98mkiv]

I'm installing a mariner pipe and boyesen reeds on my 300sx will I need to re-jet? Rest of motor is stock.

 

[silverbullet]

If you still have the 34mm bn, your not gonna be able to rejet that carb cuz the jetting is fixed.. if you have a sbn 34 or 38 you can..

 

[98mkiv]

Thanks but that does not answer my question.

 

[silverbullet]

I realize it doesn't answer your question.. but at the same time I was asking you what carb do you have? You will not be able to rejet an old round fuel pump 34mm bn carb.. I've tried, there are blocker plates where the jets should be.. I've experienced this on round body 44's too.. have you upgraded to a sbn? Have you changed the arrestor either? I have put a 38sbn on my kids 300, and have had to play with the jetting a lot to get it to run..

 

[98mkiv]

stock carb (1991) and do I need to rejet (regardless of the carb)?

 

[silverbullet]

Well.. most the time when adding a pipe to any ski it will need to be jetted... your going to have to look at your carb, if it's a round fuel pump chances are you will not be able to turn the hi screw out enough for the demands of a pipe.. if by chance you have a rectangular fuel pump and a newer sbn carb, you would be able to open it up, remove jets, see what size your at now, then probably bump up the main jet a cpl of sizes, and probably leave the low circuit alone.. but I can't give you the advice you need if you don't tell me exactly what carb you have.. most 300's come with the older 34bn carb, but it's possible someone may have upgraded yours or your model year is new enough that you'd have an sbn carb. . but only you can tell me what you have...

 

[mega_loads]

silverbullet what did you end up jetting the sbn 38 at because im doing the same. thanks

 

[silverbullet]

Mega loads.. I had to rejet several times to get it to stop loading up on the bottom.. I could make it run just fine for me, cuz I cld make it pull thru the bottom.. but my 12 year old couldn't.. I was at a 45L 85h.. it still loaded on bottom.. I wanted to go to a 40, but the local mikuni dealer didn't have one.. the smallest he had was a 37.5... I couldn't believe I had to go that small.. ultimately it's at 37.5/90.. if I pipe or boost compression, I feel I cld bump that slightly...

 

[mega_loads]

Thanks for all the info. Its saves so much time to have a starting point. Thanks again sliverbullet

 

[silverbullet]

Ha! Yeah np.. I asked ppl too, without any luck.. I originally started at 80/80.. took me several attempts to get it to transition.. my kids ski is mostly stock except for k&n, pjs h20 box, and a bore.. his is also a js not an sx.. and fiber reeds too.. this year he's getting a ported, bored, shaved, piped mill I'm building for him..

 

[mega_loads]

Sweet they are great learner skis for kids. I'm helping a buddy out doing the same for his boy.

 

[marc340]

i used a carb from a old polaris sl 750 (sbn38) i just put the throtle cam put the pop at 45psi whit a 1.5 needle 57.5 low and 110 high its stock and running for 3 year now the problem whit that motor it s vibrate so much a low speed the needle don t seat right this why you used a small 1.5 needle and high pop off for the fuel pump i used the pump from a old sea doo