SBN 38's for Dual Carb Manifold on 550sx

[E350]

I have a 1993 Kawasaki 550sx with the reed engine and 180 psi compression in each cylinder.
I would like to install the Waxracingproducts.com 550 Kawasaki Intake Manifold for SBN 38 carbs.

And I have questions.

JetManiac sells the single SBN 38 carbs for a great price, but they are single carbs. So, how do I put them together?

First, how is the pulse line run from the crankcase to the fuel pumps on each carb? Is a barbed "Y" fitting used?

Second, how is fuel run to and from the carb from and to the tank? Is a separate fuel line out used and a separate fuel return line used for each carb? For a total of four lines?

Third, how is the throttle linkage connected from the butterfly of one carb to the other? Since the carbs are single carbs, the axle for the throttle butterfly doesn't poke through the other side of the carb far enough to be grabbed by any of the Mikuni type connectors.

Fourth, how is the throttle cable connected to the rearmost carb? There is no throttle holder on the Wax manifold. But Wax does sell a fuel pump side throttle holder (but it is on the engine side, high up not like the existing 550sx oem throttle cable holder which is under the oem single Keihin carb.

550 Kawasaki intake manifold

Introducing our versatile 550 Intake Manifold, designed to fit West Coast, PJS, and SX cylinders, and allowing you to run dual 44 or dual 38 Mikuni carbs. With our multi-fit system, you purchase the base and select the carb size from our menu. If you decide to switch to a different carb size...

www.waxracingproducts.com

 

[MarkWalker]

@Hirschfelt !

 

[fastgtfairlane]

Yes you'll purchase 2 single sbn 38s. You can connect both pumps together and use a single pulse. You'll want to connect a inlet into each carb and tee the returns together back to the tank.. the front carb should be the carb that the cable attaches to. I would also purchase a throttle wheel for the cable as well. To connect them together, remove the throttle lever and spring and cut the throttle shaft down so it fits on the manifold behind the front carb. You'll need a retainer to go behind the coupler on the rear carb. You'll want to pull the shaft tight before you tighten the coupler to keep it tight. Then back out the idle speed screw until the shaft bottoms out on the front carb. Then hold the shaft closed on the rear carb to sync the carb shafts together.. as far as the wax manifold goes, he could tell you that. Jetting should be somewhere around 70 pilot, 125 main 2.0 n/s 65g spring. That should get you started. You'll want to tune from there depending on the pipe and pump/ impeller. I had dual 38s on my 550 reed engine and it ran great. I found 2 440 metal flame arrestors and ran 1 screen that worked best and keeping the water out. The k&n filters are terrible. He has the retainer and coupler as well on the site.

 

[E350]

@fastgtfairlane

This is the only thing you said that I cannot visualize, so more explanation is likely needed for me to understand:

To connect them together, remove the throttle lever and spring and cut the throttle shaft down so it fits on the manifold behind the front carb. You'll need a retainer to go behind the coupler on the rear carb. You'll want to pull the shaft tight before you tighten the coupler to keep it tight. Then back out the idle speed screw until the shaft bottoms out on the front carb. Then hold the shaft closed on the rear carb to sync the carb shafts together.. as far as the wax

It would seem the opposite to me. I.e., that there would be a long shaft which would go through both carb bodies and then the butterflies would be scewed in (and ball peened?)

Thank you brother, I have been following you since your 550sx days on PWCToday.

 

[WFO Speedracer]

When I did mine years many ago Hot Products sold a kit, it came with the couplers , a drilling guide , a drill bit and a tap , you drilled the carb the cable attaches to using the drilling guide and the drill bit , then used the tap to tap the shaft and then the an Allen screw went in with red Loctite to hold the coupler on , I am sure there are much different ways to do it by now.

 

[E350]

This is apparently the Mikuni SBN 38 carb which has the EXTENDED THROTTLE SHAFT to link them together. It is model number BN38-34-8113.

Apparently @JetManiac has them

Billet Carb Coupler

We’ve all encountered the issue where dimple-style carburetor shaft couplers slip, leaving you stranded with only one carburetor functioning. To address this, we designed ours to clamp the shaft rather than dimple it. While this approach isn’t new, we took it a step further by making our...

www.waxracingproducts.com

 

[kevbo]

I recently put a pair of 44s on a R&D 750 manifold. These manifolds place the carbs closer together and make mounting carbs more difficult. The driven carb needed the throttle stop cut, it needed 90 degree fuel fittings, and its shaft cut. The shafts were almost touching so i used a Mikuni coupler since they are a hollow barrel and will clear the shafts. I had a lovejoy style coupler like the one shown but once I drilled the cushion there wasn't much material left holding it together so I decided against it..

 

[fastgtfairlane]

All of the mikuni a/m carbs come with 90 degree fuel fittings, no choke and extended throttle shafts. Even with a set of oem 62t 38s when you replace the throttle shafts when they've worn out, the replacement shaft is also extended and you'll then connect the two carbs together with the coupler. It's very simple design don't over think it haha.

 

[E350]

Please see Mikuni chart above.

OK, so here's the deal (watch the squirrel cage of my mind spin round and round in real time).

Everybody has in stock the Super BN38-34-8113 Mikuni carb which may be used either as a single or as a dual because it has an extended throttle shaft.

But as @kevbo stated above, I don't like the idea of cutting the hollow throttle shaft down then clamping a shaft coupler down on it.

No body knows nuthin' about the Super BN38-34-8075 and Super BN38-34-8076 which CAN ONLY BE USED A DUALS. Which means to me that they are made as duals to be used as duals and if I am going to use them as duals why wouldn't I want to buy them instead of the 8113?

I actually left a message for the Aftermarket Carburetor Dept. of Mikuni USA in So. Cal. asking the above question. If and when they return my call I will post up what they say.



But in the meantime, any answers about the 8075 and 8076 would be appreciated.

Excellent discussion featuring @mikidymac here:

92 Sea Doo GTX: Replacing OEM BN38-34 8075,8076 Dual Carbs with 2 New Mikuni SB38-34-8113's

1992 Sea Doo GTX 5860. Prior owners butchered carbs. Purchased two new Mikuni BN38-34-8113's, description stated for single, dual and triple installs. Installed exterior hardware on the carbs to accomodate Mag and PTO sides, units fit perfect onto manifold intake. Question: Do these...

www.seadooforum.com

@mikidymac I know you are a Democrat and I am an anti-war Trumper, but my guess is that you have the knowledge and experience to answer whether I should buy the 8075/8076 dual carbs, where I can buy them, and whether or not they will fit on and if I even should use them on @waxhead 550 to Dual SBN38 Manifold. So, I am asking for your help please, and it will be greatly appreciated and reciprocated in any way I can.

 

[WFO Speedracer]

You are comparing apples and oranges, those Seadoo carbs don't mount inline like Yamaha 62T carbs do, they mount parallel like the Yamaha XLT80 and 1200 carbs do .

 

[E350]

Thanks WFO. How do the 8075 and 8076 mount? Are the applicable to the 550sx with Wax's Manifold?

 

[WFO Speedracer]

ummmm I just answered that , inline mounting means both carb shafts are inline with each other , if you twist both carbs 90 degrees the shaft are now parallel , that is how the Seadoo carbs are mounted.

Let me expand on that , that is how the 92-93 twin carbs are mounted , the 94-95 models are mounted inline but use I body carbs like the SXR does.

 

[kevbo]

The throttle shafts arent hollow, I was referring to the inline coupler. Mikuni couplers use a hollow cushion that goes over the shafts so they can be very close together. I have also used an aluminum spiral cut coupler that was hollow. I got an 8mm x 8mm from Ebay for $10. If I have room between the shafts I'll use lovejoy style couplers.