Kawasaki SXR i40 Carburetor Adapters

[user_error]

New Product

Do you have set of Kawasaki SXR 800 Mikuni SBN i40 carburetors you’re wanting to install but can’t find the rare SXR 800 intake manifold to mount them? We have the solution!

Our new 3-piece Kawasaki i40 intake manifold adapter allows you to mount your OEM SXR 800 SBN i40 carburetors onto a widely available Kawasaki 750 intake manifold!

No more waiting months to find an overpriced SXR 800 intake manifold to put on your 750 engine or replace your missing/damaged OEM SXR 800 intake manifold.

Billet 6061 T6 aluminum 3-piece intake manifold kit comes with everything needed to mount your carbs and go. Includes all stainless steel mounting hardware, o-rings, custom spacers, and carburetor mounting bolts. Aluminum components anodized black for corrosion protection.

$90/ea + S/H

 

[mrfist9]

Anyone have some experience with these carbs?

Have a stock sxi pro except free flowing flame arrestor (stock is also unobtainable)

Cannot get it to reliably transition no matter what I try.

 

[user_error]

Anyone have some experience with these carbs?

Have a stock sxi pro except free flowing flame arrestor (stock is also unobtainable)

Cannot get it to reliably transition no matter what I try.

The OEM Mikuni SBN i40 carbs are generally very reliable and have a great reputation. I’d recommend rebuilding them and checking your pop off if you’re running aftermarket flame arrestors. Installing aftermarket flame arrestors without adjusting the carburetor pop off pressure can make them run poorly.

 

[Storbeck]

I've been running a pair of them in an x2 and then the same motor in a chicken and have no complaints.

 

[mrfist9]

The OEM Mikuni SBN i40 carbs are generally very reliable and have a great reputation. I’d recommend rebuilding them and checking your pop off if you’re running aftermarket flame arrestors. Installing aftermarket flame arrestors without adjusting the carburetor pop off pressure can make them run poorly.

Running stock jetting, but yeah tweaked for flame arrestors done this so many times for so many skis,
conceptually understand however the carbs seem to be a pain...
2x OEM kits, tried Multiple N/S sets, 4 different pilot sets, 3 different spring sets.. I'm not crazy cannot get that bwaaa AAAAAHHH to go away. Pop-off seems to be a very touchy item on Kawi's.. Do they just not make poop for signal???

 

[Storbeck]

I might be misunderstand, but it sounds like you are saying that you've tried everything but you're also saying you have not changed jetting from stock?

What do you mean by "pilot sets"?

 

[mrfist9]

I might be misunderstand, but it sounds like you are saying that you've tried everything but you're also saying you have not changed jetting from stock?

What do you mean by "pilot sets"?

Sorry for the confusion.

Ski is bone stock beyond an impeller, primer/choke del, flame arrestor (which is actually just 701 style with 2 screens each)


Started from baseline per the book jetting.
OEM Rebuild kits
147.5
67.5
1.5N/S
(some insane stiff spring)

I have tried (1 change at a time)
70, 72.5, 75 Pilot Jet's
1.5 N/S, 2.0 N/S
Stock Springs, 80g, 95g
various combinations of the above 2

I should probably keep better notes,
I didn't even attempt the stock springs, I went straight with 95g springs, high 30's popoff, the damn thing basically was stuck in no wake mode! ha
Dropped to 80gs & 75 jets, ski became ride-able, but pretty major bog loading up on the lowend, doesn't matter idle > anything. Midrange/topend is then explosive and frankly feels pretty great albeit never did any testing there. Figured went too rich, started leaning out pilots 1 change at a time, issue never really got much or any better.

Played with many settings
Best I've had so far is
147.5
72.5
1.5N/S
80g

This setup still was a certified plug nuker & bog machine, went 70 pilots was WORSE, went up to 2.0N/S & 95g to drop pop off a tiny bit, even worse.


I wouldn't mentally rule out some sort of electrical issue or something of the sort really doubt an air leak, it idles like a top with close to stock LS settings, I intended to take the thing to really mess with it on Saturday, but frustration led me to bring a working ski instead.

It's tempting to try setting it to stock and just stacking screens in the flame arrestors and see what happens, riddle some other baseline to start with and decide the stock kawi settings are genuinely worthless (found some evidence to support that). Or set the thing on fire.

 

[WFO Speedracer]

I am not saying this is your issue but what is sometimes mistaken as a bog on a Kawi 750 is actually a bad stator , I have seen this particular issue many times , of course no amount of carb tuning will make it go away , 750 stators are easy enough to swap out and if I was working on this ski that is exactly what I would do at this point, just swap the stator , cover and all off a known good working unit and see what happens.

I also want to say this so we don't totally turn this thread into a tuning thread , this adaptor looks like a great reasonably priced option , I have several SXR800 intakes I scrounged over the years but yes they are very pricey now and really hard to come by.

 

[mrfist9]

I am not saying this is your issue but what is sometimes mistaken as a bog on a Kawi 750 is actually a bad stator , I have seen this particular issue many times , of course no amount of carb tuning will make it go away , 750 stators are easy enough to swap out and if I was working on this ski that is exactly what I would do at this point, just swap the stator , cover and all off a known good working unit and see what happens.

Are they all interchangeable 750 to 750?

I have a known goodie off a small pin couch motor... Ugh with a timing advance though.

 

[WFO Speedracer]

As far as I know yes they are all interchangable , The best factory setup is of course a complete SXR 800 ignition with the magnets removed from the flywheel , since those are DC CDI it makes a really cheap and reliable total loss system.

 

[Storbeck]

If I were you the first thing I would do is get find a plastic nozzle assembly from a 650sx. They're cheap, super easy to swap and have a way bigger bore than the super small 76mm sxi pro nozzle. This will dramatically reduce your pump load. You may or may not need that, but it's way easier to tune a ski that has too little load and then work the load higher after you're close, than to go the other way. Too much load makes tuning impossible. It's especially bad if you have a relatively high port high revving motor like an sxi pro.

Then I would make sure there's nothing actually wrong with the carbs. Check popoff by filling the little area around the seat with wd40, that way you can see if the seat o-ring is leaking and you can check for a nice clean consistant pop and make sure both carbs are the same. Then fill that little area and assemble the carbs and make sure the popoff is the same with the diaphram and plate on there (I've had carbs where the arm sat too high and the plate put pressure on the diaphram which wreaks havoc with popoff).

Put some reasonable popoff level in there, I'd go low to mid thirties.

Then go do jetting. There are great writeups with more detail out there, Paul's on PWCToday is good.

THe basics are:
Go to the lake. Turn the low speed screw in to make it leaner until it dies when you grab a handful of throttle from low speed. If you go all the way in and it's still not dying, you need a leaner low speed jet. Do that until you get a hesitation. Turn it out until that hesitation goes away. Adjust low speed jet up and down as needed until the poing where the hesitation goes away is around a turn out. You're now pretty close. You can do the stuff paul talks about in his writeup to get it more precisely dialed in if you like.

Then throw an 80mm aluminum nozzle from a couch in there, increasing pump load and see if that helps. Beware it might require a richer high speed (so maybe start a bit richer).

If that helped, keep going to the stock 76mm nozzle.

 

[Storbeck]

Oh hell didn't even realize I'm polluting product intro thread with tuning stuff.

I do think this looks like a great option. I like the i body carbs especially for an X2 because the mounting screws are so much easier to get to than "normal" sbn carbs, and the kehin intakes are so much cheaper and easier to find, so bravo on the new product.

 

[WFO Speedracer]

Oh hell didn't even realize I'm polluting product intro thread with tuning stuff.

I do think this looks like a great option. I like the i body carbs especially for an X2 because the mounting screws are so much easier to get to than "normal" sbn carbs, and the kehin intakes are so much cheaper and easier to find, so bravo on the new product.

At least it is getting to the top of the page LOL

 

[mrfist9]

Sorry lads!

Will try @Storbeck kinda hitting a lot boxes I've already hit. But I love your diminished load idea.

 

[user_error]

No such thing as bad publicity, no worries on my end, thanks guys!