300/440/550 550 carb restricter help

[aqua]

My friend has an old 550 jetski and we were wondering if there is suppose to be a restricter in the return fuel line. If so what size jet is commonly used or what is done to restrict it. Or does the carb have a restricter built in?

thanks

 

[Endo]

If it runs to a rev limiter then that has a restrictor built in the limiter. If you by passed it then yes you need a restrictor. Can't remember what jet it is but something around .025 will work for ya.

 

[Superjetqueen]

The rev limiter has been bipassed.

 

[Endo]

Then you definitely need a restrictor in the return line if it is the original round pump design.

 

[Superjetqueen]

So what size jet and where do you get them? Sorry...I am new at this stuff...

 

[#ZERO]

If it has the older Mikuni BN round body carb you will need a restrictor in the return line because I don't think the carb has one built internally.

You can tap the end of the fuel return nipple on the BN carb and install a .60 Mikuni main jet.

If it has a Mikuni SBN carb the fuel restrictor should be built into the fuel pump body right before the fuel return nipple.

Some people drill the restrictors out and use a .60 main jet in the return line.

 

[Endo]

I've never thought of tapping the outlet....I just usually jam it into the fuel line. Thanks for the info...I'm gonna have to give that a try.

 

[aqua]

I've never thought of tapping the outlet....I just usually jam it into the fuel line. Thanks for the info...I'm gonna have to give that a try.

that is the way we had one.....in the return line...fit perfectly. but the jet i stuck in there was a 137.5 and i needed it back for my sj.

superjetqueen, jets can be ordered here locally....lake ozarks or columbia or can be ordered online from parkeryamaha or LPW.

 

[Superjetqueen]

Now you tell me! Aqua, I don't know what I am going to do with you!

 

[Endo]

Hate to sound cheap (but I am!) I usually use an old jet out of what ever old carb I have laying around. Most old sleds ran round mikuni's (vm's) and are good donors. If the jets are to small a drill bit does wonders.

 

[aqua]

jets are less than 5 bucks so buying a 60 size would prolly be just as cheap as buying the bit to drill one out.

 

[x2ryder]

I just put a SBN 44 on my 87 550. I am not sure if it already had a built in restrictor in the carb or not? The carb came off an old superjet I was told. So I used a 125 mikuni main out of one of my sbn's in the return line. Is this ok?

 

[Endo]

If I remember right a sbn's is internal (no restrictor need) and the bn is external (you need a restrictor in the fuel line). Hopefully one of the other old school guys will chime in and help with this.

 

[x2ryder]

Yeah I was told some of the old SJ carbs did not have a fuel line restrictor. Any help is always greatly appreciated.