SX/SXi/SXi Pro 1999 SXI PRO (It's 2025, I have 9 Skis, SEND HELP)

[mrfist9]

Went on a trip again to visit my good buddy in Alabama!... This time just a double, no car trailer thankfully.
We needed a replacement motor for a friends 550, and a friend (who got cold feet) wanted the sxi pro

So stared at the weather all weekend like a hawk, we got 3 inches of snow here in ATL, and immediately it turned to a slushy mess.
Managed to have some fun though with friends before it all rinsed away.


Seller was in stock at his lake residence where he stores his fun stuff, so wanted to get the job done. Saw a good slot on Saturday where we could get back before temps got too low and everything froze back over.

Made the Journey!
I wasn't going to back out of the SXI PRO after agreeing to purchase it, decided I'll make something of it we know I love a good project. Got all sorts of various parts & engines.... But alas I had a double.. with one empty slot.. So we know what happened.


Obligatory Buc-ee's Picture


Finally All home, ZERO road drama, nobody was out, roads were gross but zero holdups.





NEXT DAY:

Let's start with a quick detour...
1988 650SX.. It's going to a buddy but we can talk about my short ownership.
I knew it was a good unit, didn't bother trying to run it or anything there, probably hasn't ran in years.
Some liquid encouragement she fired right up!

Back to the pro... Got it all cleaned up and out in the sun.







Plan is typical whole refresh.
Some pain points I'm not overly stoked about.

Fiberglass repairs:



something is DEFINITELY hiding under this sticker


Missing parts:
I have the i-body carbs... yes I know "jUsT rUn tHe foRTY sIx"
I am in need of the manifold and airbox arrangement. missing those pieces... DM me if you have!



Either way should be a fun little project when I have the time!

 

[brapperdoodle]

something is DEFINITELY hiding under this sticker
View attachment 452990

Don't touch it, ignorance is bliss

 

[mrfist9]

Don't touch it, ignorance is bliss

At minimum a more attractive stickers necessary

 

[mrfist9]

For the first time actually wrenched on this thing. Finally got a twin mikuni 40 manifold apparently on the way. So figured I'd investigate.

Ripped off the intake manifold & the old junk fuel lines.



I realized the Kawasaki Green wasn't exactly right, cause the single carb manifold on it matched perfectly which was odd. So I proceeded to spend the next 30 minutes looking up part numbers to convince myself I actually had an sxipro engine here.

All checked out, guess someone repainted it to clean it up one day, original pistons in there etc. You can see the color difference in the intake ports. D head, cylinder part # ending in 29 which matches the parts diagrams.


I always complain about it but there's something therapeutic about cleaning the studs, chasing the holes and reinstalling all nice and clean.




Kinda at a weird stage, I'm not sure I have any belief that the Reed stuffers are helping. Same with the stock MLS outer Reed gaskets. I'm thinking I'm going to run no stuffers and just use 2 inner gaskets, I mean the stuffer & gasket themselves are both smaller than the intake manifold ports. Seems kinda counter intuitive, but what do I know.






So the next fun curveball. So I have this R&D pipe. Think we will start without it but we got options. Wish I could find some instructions, I know it's a top end pipe, sure I could optimize it to be a bit more fun if I drill it out a bit.

It's mostly fueling very little data about. I was gonna go off the factory pipe instructions for jetting but that just recommends basically stock carbs settings which sounds a bit surreal




More research to be done!

 

[mrfist9]

Okay Got the sxr intake manifold... turns out the gaskets and stuffers mate up perfectly. oddly the pins on the manifold to align the carbs are way too long... maybe the sxr carbs are chewed out a bit deeper in the carb body... guess ill just cut them down.
Carbs are also HIDEOUS inside, one jet was NOT fun. oh well.. would love to find a stock airbox but probably a tall order.




SERIOUSLY WHO DOES THIS??? both were like this I couldn't believe it

 

[Jiffyjet]

For the first time actually wrenched on this thing. Finally got a twin mikuni 40 manifold apparently on the way. So figured I'd investigate.

Ripped off the intake manifold & the old junk fuel lines.

View attachment 454125

I realized the Kawasaki Green wasn't exactly right, cause the single carb manifold on it matched perfectly which was odd. So I proceeded to spend the next 30 minutes looking up part numbers to convince myself I actually had an sxipro engine here.

All checked out, guess someone repainted it to clean it up one day, original pistons in there etc. You can see the color difference in the intake ports. D head, cylinder part # ending in 29 which matches the parts diagrams.


I always complain about it but there's something therapeutic about cleaning the studs, chasing the holes and reinstalling all nice and clean.

View attachment 454126


Kinda at a weird stage, I'm not sure I have any belief that the Reed stuffers are helping. Same with the stock MLS outer Reed gaskets. I'm thinking I'm going to run no stuffers and just use 2 inner gaskets, I mean the stuffer & gasket themselves are both smaller than the intake manifold ports. Seems kinda counter intuitive, but what do I know.

View attachment 454127

View attachment 454128


So the next fun curveball. So I have this R&D pipe. Think we will start without it but we got options. Wish I could find some instructions, I know it's a top end pipe, sure I could optimize it to be a bit more fun if I drill it out a bit.

It's mostly fueling very little data about. I was gonna go off the factory pipe instructions for jetting but that just recommends basically stock carbs settings which sounds a bit surreal

View attachment 454129


More research to be done!

 

[kevbo]

Make sure the carbs are perfectly clean and do initial runs with the stock pipe. It will be easier to burn a piston with the aftermarket pipe. Also get the bracket that connects the exhaust to the cylinder, It will also have the throttle cable mount built in.

 

[spinyard]

It’s cool to watch someone else do this thanks for sharing

 

[mrfist9]

So I've purposely avoided staring at this thing too closely... Then I spotted the main feed line.



So pipe off.... Kinda frustrating I've convinced myself I'm sticking stock pipe for now so annoying buying more gaskets.



Cleaned the tank, ran fuel lines, got the kevbo bracket, rebuilt carbs, mocked up the battery cables and ordered some up.

Prince is running so this is now priority #1

 

[mrfist9]

Carbs rebuilt
Went for a sort of tweaked stock specs off of frankly just a little experience at this point.

147.5 H stock
67.5 L stock
1.5 N/S stock
95g springs pop off ~35PSI stock was ~50
HS 1.25 (stock 1 +-0.25)
LS 0.75 (stock 0.5 +-0.25)

I figured without stock air box, I should atleast be at the richer end of the stock spectrum as a starting point. As well slightly lower pop off. Some research on the ole search feature I found 3 things.

1. Dropping Pop off helps a lot in this setup vs stock
2. Increasing to 72.5 or 75 Low jets helps. Factory pipe asks for a 75 low stock 147.5 high interestingly.
3. Epoxy the crossover...DOH

See what she do.

Got new battery cables in and installed.
Cut back the plug wires, both took 1/2-3/4in to get some copper back.

Close just need exhaust gaskets... Supposed to show up tomorrow.

 

[mrfist9]

Exhaust back on. Easy job.

Took some tinkering to get it happy idling. Old setup definitely flooded it out like a mad man, just spit out tons of disgusting fuel out the back.

.75 LS didn't work well, 0.5 was worse, landed at 1 turn on both carbs

Went up to 1.5 on the HS just out of security. Some more research sounds like the stock box on these is actually super restrictive... See how a test day goes but the answer may be those 75 low jets.

She's a runner though! Ready for testing.

 

[mrfist9]

So testing came and went.

Bad news. Ran like S**T.

It idles fairly well, but loaded up in the water it hits this weird idle > low/mid range transition bog/wall that nukes the plugs & stalls it out.

However. I got it ~3-4x on the trailer to skirt past that point and it sounds so healthy up top.

End of the day pulled it out. Wanted to see if I could get any different results on water while still had a buddy there to pull me out if needed. Tried some different plugs, tinkered a bit. In 10 minutes of putting around I got it out of the idle loop once! And it was a ripper!!!... For maybe 8 seconds and I had to slow down. oh well inspiration to fix it.

So got it home. Got some dinner.
Did some quick research.... Found an old post of a guy with similar symptoms who discovered a corroded up stop switch. Which reminded me of this guy.



Opened up the switches on the handlebars... Start switch was corroded a bit, plunger was trashed.. swapped the plunger for a freshie and did some new connectors. Unlikely fix, but checking off some boxes.



Next checked the stator & flywheel, first look inside for me on this 750. Checking another box. Not a 10/10 but she's atleast an 8.5 in there. Cleaned up the stator magnets with some elec contact cleaner and bolted it back up.




So let's get down to real business here.
My masterful carb tuning is probably the cause.

I decided f*CK it. Pulled the carbs. Changed my LS jets to 75s. Swapped out the 95g springs to 80g. Seems....
-plausible low 40s pop off is too high.
-pausible 67.5 pilot jets (stock) are too small when you don't have the pencil eraser sized air inlet of the stock airbox.





All back together. Redid the rear wire, I wasn't happiest with the wire cap. Unfortunately I've ran out of what I thought was an endless supply of those seadoo caps. Oh well.

If I find some more time before next attempt to test. I'd like to ohm out the ignition coil itself, I've had issues in the past with just old decayed plug wires.

Was late but started it up quickly. Seems kinda promising. It really doesn't illicit these terrible behaviors out of water. But minutes before pulling the carbs I had it idling and as quickly as I could yanked WOT and it was hesitating pretty bad. Doing this same test now rejet. It did NOT have that odd WAAAAMMP sound and revved out smoothly.

Fingers crossed

 

[mrfist9]

Okay so rode it today! It f**king worked.

Water still way too cold but did some good WOT rips on it, felt good, stable, little slow but hey progress.
Only really issue was it was pretty lazy on the bottom... like a kinda slump in the low to mid then explodes in the midrange.

Took it back, plugs a bit cooked, wash pretty rich looking.



So gonna drop down from 75 > 72.5 & turn in the HS from 1.5 on both to 1.
See what the next test session looks like.

 

[mrfist9]

Successfully swapped down to 72.5's hope it's enough. Got some 70s just in case. I've read a little how folks ran into dribbling and went up to 2.0N/S. Honestly just rather let it leak lol.

Wanted to inspect I had the correct 3738 CDI with the advanced curve higher limiter blah blah.


The stock foam pad was a solid rock at this point and had this ugly turf stacked on top.



Finally got around to a hydroturf order so replaced with a new HT one and a piece of leftover turf. Looks way better and makes me feel better about the pole slamming down on it.

 

[mrfist9]

Alrighty tuning this has been a pain. So much so I'm going to attempt a fresh start. I need to carve out a day to just sit there at the ramp and figure it out.

Grabbed my words from another thread:


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.

So I wanna restart with this thing.
Some things I know
-Stock Total jetting = 147.5 + 67.5 = 215
-Looking at any ski I've ever done something similar I seem to land around 2 points overall higher than stock so lets target 220 and work our way back
-Basically anything I can find of anyone having success with this setup lands around ~32PSI
-Many mention dribbling as an issue with these so 2.0 vs 1.5 seems like a step in the right direction.

So I'm gonna set myself up to tough it out for a tuning day.

Going to start with
147.5
72.5
2.0 115g (32psi)

Same as my best setup to date, except slightly lower popoff that setup was 1.5 80g

@Storbeck mentioned running a looser nozzle for testing... I like that gonna check my stash
@WFO Speedracer mentioned the stator, I'm gonna at minimum hit it with the book test.


Also planning to bring more 701 screens to shove in my arrestors as a hail mary if I'm desperate

 

[WFO Speedracer]

You say it is a hail Mary but I was trying to fix a XLT 800 that someone had removed the choke shafts on, (this is an absolute no no on an 800 Yamaha BTW )

It had a serious low end bog and took about a mile to plane out , once it planed out it ran really well , till you went back to idle again .

The fix turned out to be stacking two of the stainless flame arrestor plates on top of each other, since they are stamped from a sheet of perforated stock no two are exactly alike which means the holes don't quite line up, it was just enough restriction to fix the low end bog issue.

 

[mrfist9]

You say it is a hail Mary but I was trying to fix a XLT 800 that someone had removed the choke shafts on, (this is an absolute no no on an 800 Yamaha BTW )

It had a serious low end bog and took about a mile to plane out , once it planed out it ran really well , till you went back to idle again .

The fix turned out to be stacking two of the stainless flame arrestor plates on top of each other, since they are stamped from a sheet of perforated stock no two are exactly alike which means the holes don't quite line up, it was just enough restriction to fix the low end bog issue.

Yeah seems like a real possible deal. The more I think about the way they made this thing work stock, with the increased air velocity, reed stuffers and a tighter intake tract, of course it's a pain.

 

[WFO Speedracer]

My basic rule of thumb is high restriction , high popoff, low restriction , low popoff required , it has more to do with vacuum signal than anything else , think how a vacuum cleaner works, it produces a set amount of vacuum with a given nozzle size, make the nozzle smaller the vacuum goes up, make it larger like just the end of the hose the vacuum signal is much less.

When you are dealing with I body carbs, all I body carbs are EPA carbs , they are all set up with high restriction, that means more vacuum signal and it breaks up the fuel droplets more readily allowing a lean mixture that satisfies the EPA requirements , they were never really designed for performance applications.

 

[mrfist9]

My basic rule of thumb is high restriction , high popoff, low restriction , low popoff required , it has more to do with vacuum signal than anything else , think how a vacuum cleaner works, it produces a set amount of vacuum with a given nozzle size, make the nozzle smaller the vacuum goes up, make it larger like just the end of the hose the vacuum signal is much less.

When you are dealing with I body carbs, all I body carbs are EPA carbs , they are all set up with high restriction, that means more vacuum signal and it breaks up the fuel droplets more readily allowing a lean mixture that satisfies the EPA requirements , they were never really designed for performance applications.

So the dirty of this ski is frankly I don't like riding it. I had the idea in the back of my head.. get it dialed in here, drag it over to the JS440. Tons of people swear by these carbs but I frankly wonder if I'd be happier with some setup ported/geared towards twin SBN44's. Dump this thing entirely.

The statement alone "not designed for performance applications" just feel like I'm barking up the wrong tree I'll jump off anyway.

 

[Storbeck]

I've heard people say they are epa carbs and such, I have no idea where they are getting that idea.

I've ridden multiple skis with those carbs that run great, including my own.

Just don't see what's wrong with them.

I guess I should be happy if other people don't want them then the price will go down for me.

In the entire time you've been trying to tune this thing have you ever had it lean enough to hesitate?

Have you made any attempt to tune pump?