300/440/550 Help me choose which carb for my JS550

[Dan Rudd]

We're looking at adding a Mikuni SBN to our 89 JS550 which currently has the BN. We just can't get that BN to tune no matter how much we tinker with it and we want some more reliability.

The motor has a fresh complete rebuild. The ski has the following mods.
Ocean Pro head
Ocean Pro intake
Coffman half pipe
DG waterbox
All the handling goodies, impeller, grate, ride plate, etc etc

When looking at carbs on-lline we find a couple that have their specs listed. Being new to this carb I don't have a clue where to start. If someone knows their way around this carb please give me your 2 cents on which carb I should consider.

Carb#1
120 Low
140 High
2.5 Needle
80 gram spring

Carb#2
100 Low
125 High
2.5 Needle
65 gram spring

Thanks,
Dan

 

[D-Roc]

Find a single carb off a 701 superjet, get the spacer plate and bolt it on.

 

[Dan Rudd]

The OP manifold is angled and doesn't require a spacer. I'm reluctant to buy a used carb because I don't want to run the risk of buying someone elses troubles. I hoped that if I bought something new it would be one less this to worry about.
My issue is that with the mods to my sons ski I'm not sure where to start with the jetting.

Thanks,
Dan

 

[D-Roc]

Do what you want, but an oem 44 sbn carb of of a 95 sn is what I put on my 550's without a jetting change. Best mod for the old 550's IMO.

 

[Dan Rudd]

D-Roc,
Were your 550's stock or had you done much to them? I wonder how that effects jetting.
I'd be good with a used carb (would sure like the price difference!) if I could find one I felf I could trust.

Thanks,
Dan

 

[D-Roc]

I had it bored out a bit, piped and milled head. Probably a few other old skool tricks. The other one was stockish with not much done to it. Both started the ski much better and made tuning possible on the old piston port motors.