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New to Me: Modded 97 SPX

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Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#1
I recently picked up a 97 SPX with several performance mods.​
It has a TDR water box, Mikuni remote fuel pump setup (improperly mounted to the engine) with a Team Butch block-off plate, Novi MaxFlow intake and flame arrestors, and maybe a different Pipe? It's purple.​
Compression on both cylinders is 125 psi and the engine appears to have been rebuilt at some time.​
I'm currently replacing and cleaning the fuel system and I'm looking for advice on a good starting point for jetting, pop-off, spring weight, N&S size. Thanks in advance!​
 
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mikidymac

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#3
That’s a stock pipe and probably too much carb for a stock pipe. I am sure that thing had a aftermarket pipe at some point.
@Matt Braley will have info on the carbs and intake.

If your compression tester is accurate that top end is done. At 125 psi it will be hard to start and barely run.
 
Messages
25
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0
Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#4
Yep compression has me concerned, but they're even. I'm going to retest with a different tester.

Just took the carbs off. Here's what's in them:

Main 120

Pilot 130

N&S 1.5

Pop-off: mag 30 pto 34

Pop-off tested with needle exposed and cavity filled with fuel
 

Matt Braley

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#5
Sounds like too much fuel and too much pop off. I'd like to see down the throats of those carbs and then I would know who modified them. Is that intake manifold cracked across the top?
 
Messages
25
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0
Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#6
Is that intake manifold cracked across the top?
I noticed that too when I pulled the carbs. There isn't anything continuing down the sides of the manifold, but I'm going to pull it and check it. Hope I can come across one if I need a new one...

Here's some pictures of the carbs. @Matt Braley can you give me any info on these? They're stock carbs, with the bases modified?


(vacuum caps were for pop-off test only, not being run)





 
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Matt Braley

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I can't keep up with it anymore. I've got some really cool skis!!
#7
The carbs start life as Mikuni Super BN44's and are modified from there. These went through someone's carb shop but I'm not sure who, probably Team Butch who was one of Seadoo's top race teams. It was an early job like late 94 or 95. You can see that they polished them up on the inside and they may have been bored to 46mm, you will have to measure the opening on the bottom. If they are 46mm then the "fat" jetting would make more sense to me. Normally 44's have a total jetting of 235-245 and you are at 250.
 
Messages
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Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#8
I'll mic them tonight. Sounds like I'm getting closer to some initial settings, barring a horrendous vacuum leak, or truly low compression. Tool truck comes this week with a new compression tester for me. I used a cheap one for the test
 
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Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#9
Took the intake manifold off to check for a crack. Once I got it in better lighting I was relieved to see that the suspected crack is just CNC paths. You can see them in a couple other spots on it too.

I mic'd my carbs, they're 45mm on the intake side. The intake plenums are 47 at their widest point and taper down to 41mm.

Still waiting on my new compression tester, but assuming the engine is actually healthy, does anybody have a suggestion on where to start for jetting?
 
Messages
25
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Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#11
I tried it when I first cleaned the carbs. The setup they had was dumping fuel and immediately fouling the spark plugs. That was with 2.0 n&s. The 1.5 is way too lean
 

Matt Braley

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I can't keep up with it anymore. I've got some really cool skis!!
#14
You can just leave it right there if your going to run smaller low speed jets.
 
Messages
25
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Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#15
Ok cool. Last question for now, I'm going to change out my exhaust pipe and water box. Any recommendations on the water box? I'm eyeballing a certain Neptune pipe that's currently for sale...
 

Matt Braley

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I can't keep up with it anymore. I've got some really cool skis!!
#16
I LOVE a Neptune pipe! Chester is a first class guy also so nobody more solid to be getting your goodies from. The 97SPX waterbox flows better then the rest. I sell them for $100 shipped but if you keep an eye out you can find them sneaking through eBay cheaper. It must be out of a 97 SPX, others look almost the same but are different.
 
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Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#18
After more research, I'm going to stick with a wet pipe for this season.

The tool truck finally came by the shop with my new compression tester. I had originally been using a cheap Amazon special.

With the new tester, my averaged numbers are 170psi mag 168psi pto with the intake manifold off the motor.

Would those numbers indicate engine modifications?
 

mikidymac

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#19
Yes, stock is 150 psi. The head in your picture looks stock so it was probably just milled for a little more compression.
 
Messages
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Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#20
I've been riding the SPX for a couple weeks now. The thing rips!

My final jetting wound up being

pilot 125
main 120
N&S 2.0
pop off 25

Since I had time while it was down, I went through the ski and fixed a few other issues I'm glad I found. Replaced fuel lines, the rotary valve was off one tooth to the right, leaking rave gaskets, leaking water regulator, a hole in the exhaust hose between pipe and muffler. I switched to an OEM muffler while I was there. The previous owner replaced the VTS system with a manual trim and an R&D nozzle so I pulled the rest of the (hacked and cut) wiring harness out of the hull, ordered an GTX start/stop switch to delete the VTS switch, and I ordered an OEM tachometer to replace the VTS gauge. I'll post pictures of how that turns out.

I wouldn't say its quite as fun as the stand-up but I'm absolutely keeping it and making it mine. I have found the 787 engine to be pretty neat and fun to work on and learn about. Thanks to mikidymac and Matt for the help!


Where is the most widely accepted location to mount a remote fuel pump in these hulls?
 

Matt Braley

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Location
Niceville, Fl
Water Crafts
I can't keep up with it anymore. I've got some really cool skis!!
#21
Happy to hear your enjoying it. A lot of the old race skis mounted the fuel pump on the deck just forward of the space the flame arrestors occupy. I like the impulse line to be shorter then that though. You can epoxy a mount down in the hull.
 
Messages
25
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0
Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#22
So I noticed my rave valves were leaking around the base gaskets. Earlier this summer I replaced the caps and bellows with oem parts but didnt remove the bodies.

While disassembling the valves to replace the base gaskets I found that both of the bellows had slipped off the plastic caps and that's what was leaking. After some examination I found that the springs can be adjusted by being screwed into the ends. I clipped 3/8" off each spring and reinstalled the bellows with a tighter fit. I'll reinspect them after I run it again. Zip ties I guess would be next if that doesn't work.

Pulling the guillatines I found the mag side was damaged (pic). What is that kind of wear telling me?



 

Matt Braley

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Messages
6,957
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Location
Niceville, Fl
Water Crafts
I can't keep up with it anymore. I've got some really cool skis!!
#23
The problem is the shaft your fingers are touching. It starts at 10mm but wears thinner as the housing hole gets larger. Eventually the clearance is too great and too much exhaust heat gets by it kicking the bellows off and running black exhaust juice down the side of the cylinder.
 
Messages
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0
Location
Eagle Mountain
Water Crafts
1997 SPX
1997 GSX
1986 JS550
#24
I see. So I'll replace both housings and slides. I still have at least a couple more weeks of riding left, hopefully. If it stops raining.

Sounds like I need to do a leak test also. Can my pop-off gauge handle that?
 

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