Js300sx upgraded carb to 38mm

[Matt morzhov]

1. So I broke the tip of my needle on my 34mm mikuni was wondering how people got a broken tip out?
2. Had a 38mm mikuni laying around so I threw it on the 300 set high and low at 1.5 turns seemed to run fine but haven’t tested it on the water yet but was wondering if anyone has done this upgrade and what they set the high and low at. Believe it has a 1.5 needle

 

[WFO Speedracer]

Yep learned that one years ago and passed the info along , the SBN 38 mm carb off of a WR500 is a direct bolt on , jetting and all bonus is a slight power increase.

Also with a little modification a 650SX head gasket can be cut in half and used to raise the compression , these are both small power increases but small things add up.

 

[Matt morzhov]

the one I put on is a round body 38 and on further messing around seems to be revving pretty high at start up and when you give it gas is Boggs out and dies.

 

[WFO Speedracer]

My advice find a SBN carb, tons of them on older Seadoos 91 -95 , any of them will work if you change the jetting but the chokes won't hook up and you have to run a primer , the WR500 one is a direct bolt on , jetting is correct, choke hooks right up like stock.

Those old BN carbs were quite finicky , the 38's were ok and you could dial them in to run pretty well , most of the 44's had serious issues that no one could straighten out.

https://www.pwctoday.com/forum/technical-discussion/vintage-skis/133674-