300/440/550 js300 sbn38 jetting specs

yamarider · May 12, 2011

I have a js300 with almost every bolt on accessory available for them. I love these skis so much just to spite the haters really. At the moment im running a bn38 on my 300. I have a sbn38 that I would prefer to run but cant seem to get the jetting right.

Has anyone ever had any luck with tuning a sbn38mm carb on a js300 i would really like to know your jetting specs.

Cheers.

DMan II-40 · May 21, 2011

It is so hard to find information on js300 skis (since almost everyone hates them). I have an 86 js300 that im trying to get started right now. After that I will probably (hopefully) ride it around this whole summer then get into modding it. What mods do you have on your 300? are the pipes for the 300 specific to that motor or can you use 440 and 550 pipes?

yamarider · May 22, 2011

Im not sure if everyone hates them or if there are just not many still running after 25 years. They take a bit of patience to keep running and the simplicity of doing a motor swap to a 550 gets too tempting for most people. I have a kerker pipe, carbon reeds, reed spacer, bn38 carb k&n air filter, ported barrel, milled head, dual cooling, advance timing, lightened flywheel, ign update kit (seperate coil and cdi). skat trak prop, pjs scoop grate and westcoast rideplate, 500gph bilge pump and a bunch of other things i cant remember atm. It really works hard for a 300!

DMan II-40 · May 22, 2011

Sounds baller. I know the 650sx motor is very similar (like the pistons are the same), are the reeds the same, any other interchangeable upgrade parts?

yamarider · May 23, 2011

I have heard that cutting a 650 head gasket in half makes 2 js300 head gaskets other then that the 300 is a unique piece of equipment unlike any other jetski.

yamarider · May 23, 2011

DMan II-40 · May 23, 2011

Cool well thanks for the info (and cool kerker install document). Guess I have to just search, but still finding the info and parts is a pain

509freerider · Jun 2, 2011

I have the 38SBN on my 300sx, basically just bolted up and adjusted the screws a bit and it was spot on, lucky I guess. That was with the stock pipe, installed a Mariner and running into bogging issues and pipe over heating. If its something you really need to know, I can pop my carb apart quick and get them to you.

yamarider · Jun 6, 2011

If its not too much of a hassle im really keen on those jetting specs! cheers