Pimp My Superjet - MSRP Build

Got about 1.5 tanks through it now. Might play around with the pop-off pressure (go down from 115g to 95g spring) but I'm going to wait until I'm though this tank of 32:1 and go to the regular mixture. Pull from 1/4 to 1/2+ throttle is very strong. Pull from 1/8th-ish to 1/4 throttle occasionally has a very slight hesitation - it may be a rich hesitation though so I want to wait until I'm using the regular premix ratio.

Did a few full throttle blips and the speed during a busy lake day is a little too fast for my liking haha - it'll be fun to try and GPS to see what this thing does during a calm weekday evening - I have a feeling I won't be bored of the power this thing puts out.

Also might have to turn the idle down just a touch - had a friend try it out and bail, had the lanyard slip off his wrist and it idled like a tanker ship faster than I could race after it in my kayak. Looked like a bunch of fools and thankfully someone in their boat was kind enough to commandeer it and rip the lanyard out. That will be the last time I let someone try it if they don't have their own ski to offer as collateral! I think the idle is just a touch too high because I'm used to the skis turning circles - but I may also have an issue because the ski is very well balanced with the ETX12 battery, custom battery box (pushes the battery 1" closer to center of ski) and the generously proportioned dry pipe - so maybe a lightweight stainless spring on the turn plate? (or maybe just don't lend it out to n00bs?)
 
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Quinc

Buy a Superjet
Location
California
Hook the lanyard to the persons life vest buckle so you dont have to worry about it coming off. That exhaust doesn't make great low end power by itself. You will want to get msd water injection and/or lighten the flywheel and get a zeeltronics to give you that low end snap until the pipe takes over.
 
Hook the lanyard to the persons life vest buckle so you dont have to worry about it coming off. That exhaust doesn't make great low end power by itself. You will want to get msd water injection and/or lighten the flywheel and get a zeeltronics to give you that low end snap until the pipe takes over.

Yea I'm kinda excited to try water injection once I find a good used setup - most of the ones I've found are pretty knackered. Glad I went with this pipe because the hit of power up in the mid is exhilarating. I'll probably look into that Zeel setup this winter as well when I have some downtime.
 
Ski has been solid as a rock all summer! 15 or more jugs of gas through it and still lovin it.

Got to ride an 08+ hull last night and while that was possibly an interest of mine (transferring the driveline over), after riding it, it's just too race-style feeling and not as flickable in my opinion - horses for courses and that ain't my style.

I would love to get a 'super' superjet A/M Hull at some point - no idea which hull specifically to look for but basically I'd like to get something that does everything the pre-08 hull does well but is lighter and possibly +1 or +2 on the carving points.

Also found this today on Facebook - apparently my ski was infamous in it's previous life! That's my ski a few years ago. Though it was funny haha.

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Well Christmas came early! Placed my order for a B-Pipe on Aug 2nd and the pipe arrived about a week ago!

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I took some time after reading online to tune the water injection screws (I replaced these immediately with the Hot Products socket cap screw replacements to avoid the inevitable frozen/stripped screw issue - hopefully!). Basically I setup the head pipe and stinger water inlet to feed off my garden hose. I was able to get the bottom and mid screw setup to have the bottom with a fine mist and the mid screw with a slight trickle and fine mist at max pressure (60psi). The top screw was closed and confirmed to not leak even at 60psi. This was all enlightening and I recommend anyone who just got their first B-Pipe to play around with the screw adjustments off the ski like this to learn exactly how they work and behave with minute adjustments.

The pipe stinger inlet got a flow control valve - so at idle it has no flow but above idle it will allow water - no further flow restriction after that. I've had this dang flow control valve since I did my 550sx hull molestification project a decade ago so it was nice to finally use!

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The installation was pretty straight forward. This is a Mod pipe - so a little shorter than the Limited pipe. I did experience contact between the pipe and the reinforcement ribs on the hull - this was not a surprise. I attempted to dent the pipe where it was rubbing but this happened to be right on a weld on the pipe. After 'massaging' it with a hammer I managed to get the 1/8" clearance I was after but I did put a slight crack in the weld (verified with a few PSI pressure test and soapy water). So off to the TIG welder again... this time it was a lot easier since the pipe was still brand new (no carbon contamination). Hopefully this weld holds up just fine - it was only about 1/2" long and I tired to keep the heat down. I stuffed a piece of gym floor mat between the pipe and hull then zip tied it to a mount at the top of the hood seal. DONE!

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Here's my water routing - if anyone wants to re-circulate it to maybe help or more likely provide confusion to the 99 other water routing diagrams out there lol.

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Water screw adjustments to start with:
A = closed
B = 1/4 - 1/2 turn open
C = 1/2 - 3/4 turn open

My final question was on jetting / popoff going from the big Type4 dry pipe to this Mod B-Pipe. After consulting with JetManiac he suggested simply sticking with the jetting that worked on the Type 4 for the initial run and adjusting the H/L screws to get things to idle/perform after that.

Good thing I listened! The pipe absolutely rips everywhere. There's the inevitable loss of top end and over-rev that only a super gigantic dry pipe can provide but DAMN! the bottom to mid response is just awesome. I'm a convert for sure - the power delivery from my setup now is basically perfect for playing around - it's like a new ski all over again!

I pulled the ski over to the shore a few times to check pipe / water box temps - water splashed onto both never sizzled, if anything they may both be too cold - but for how well it performs I'm just gonna leave it as-is until next season.

The water was around 61 today up here in Denver, Colorado - perfect day for a rip and absolutely stoked at how well the ski is running now. Gonna look into a lowered hood / cowl setup this winter with a hand hold to further fine tune my classic freestyle skillz!

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About the lanyard thing. I've seen too many close calls I don't even bother with them on my personal ski. On my friend/gf ski I make them strap it to their life jacket.

Me? I zip tie the switch open and set the idle to almost nothing so it won't run without my finger on the throttle. I also keep a broken lanyard hanging on my life jacket so, in the event I get harassed by water cops, the zip tie was a one time deal. Too many failures from cheap lanyards breaking I just said enough's enough
 
New Engine Time...

After many hours and 3 seasons on the JM 718 motor (it's about 754cc now, not by choice) I have started to find a niche in riding preference. The JM is undeniably a solid arm ripper, but I've started to adopt a more adventure jet skiing (ADVSKI - I trademarked it, jk) style of riding which involves 40-50 mile group rides packed with following high mountain/desert lake coast lines, finding remote coves, jumping boat wake, plenty of old skewl trickery and the occasional buoy session. I started to get curious about what a 760 would feel like... I also really like making stuff, almost to a masochist extent some time. Let me preface this build with this realization - Jetmaniac could easily charge a lot more for his motors and it would still be an amazing deal - this is not easy stuff and there are so many opportunities to instantly turn a motor into garbage, potentially costing you hundreds if not thousands.

Over the last year and a half, I've compiled a hodgepodge of 760 parts and started the process of making a motor out of them this summer. After many hours on the water I had a very good idea of what type of power curve I wanted and I knew that being able to hold it WOT, and having a mid rpm pipe hit were high up there - but most importantly I wanted to keep the excellent throttle response I'm used to with a ported motor. I did a lot of research on the 760 builds on here, what people like and don't like about them, and started to compile a list of what I would do if I built a 760.

I knew that an excessively wide exhaust port would not allow me to have WOT fun. I studied exhaust port shapes in general and decided on trying the yamanube template combined with careful intake port matching, intake side sleeve trimming and then finished with media blasted transfer tunnels. I didn't go wider like a lot recommend given the 701 vs 760 bore diameter, etc. I wanted to keep this ski around the safe limit of exhaust port width for rec riding. I did all the porting / blasting and then had it bored 0.5mm over (84.5mm).

So I went down the rabbit hole of getting a 1/4 straight rotary tool and a 1/8" right angle rotary tool. I used a VEVOR 500W 1/4" and a no-name pneumatic right angle as the pneumatic right angles are way cheaper than any right angle tool head for the electric rotary machines. Both worked great. I got aluminum and double cut carbine burr sets both in 1/8" and 1/4" shank for all the work. aluminum = wider single cut style for hogging work, double cut = steel work (can do aluminum as well but clogs up way easier). Get a steel brush to clean your burrs every few minutes and spray them with WD40 to help with material adhesion.


Below is the Cylinder porting work. Note - I did not raise the exhaust port even a micron. I read enough about this porting mistake on 760s to know better. The top profile in the pic below is actually more rounded than it appears - it's just the angle and it's more of a squished octagon.

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I filled the 760 intake manifold crossover after cutting a 'lock in' groove with a ball burr to keep the JB Weld from shifting. - simple enough.

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I haagen daz cases out by finger porting (filled the intake side top case voids as well as the flywheel side wth JB weld - again using the lock in groove method, not pictured, as these are where you mill into for finger porting)

1) Initial grinding - basically have no idea what I'm doing here. Just jamming a big 1/4" aluminum burr into the edges trying to get a finger groove going.
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2) Getting a little better - still not finished - but much bigger reliefs now and can see the JB weld so you know you've done some work.
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3) After masking all seal and bearing areas with T-Rex tape, I media blasted most of the contact surfaces to get a relatively uniform finish. I used 80grit aluminum oxide on both cylinder transfer tunnels and the top case halves.
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I didn't do lower epoxy feed ramps / stuffers like you see in a lot of case work.

Slapped it all back together. I'm using an older non-girdled RIVA head with 84mm 38cc domes. Might try and either remove the base gasket or find 35cc/36cc domes this winter - base gasket removal seems like a win/win and it's "Free". The Riva head got all new o-rings.
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The carbs are the cursed OEM SBN 44s. I thoroughly cleaned them and rebuilt them. Made a custom throttle cable mount for flywheel side mounting as well as drilled and tapped 2 new threaded holes to put it on that side - since most 760 intakes are the wrong side.

I'm too crafty and cheap to buy t-handle adjusters. So I made my own with some 3/32 316L tig filler rod. For the low speed screws I just did a 25amp fusion zap with the tig. For the brass I used a 45T (high silver content) brazing rod - worked amazingly well.
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Dual fuel lines, dual fuel pickups.
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Tossed it in, with some fresh hose.
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The carbs hit my lowered hood. Simple enough to fix... cut out a football shape and utilized my underwater basket weaving skillz.

Some other tidbits on the engine include some NOS Boyesen reeds I found, 1 screen in the flame arrestors and a stock 760 intake box.

Ride Report

I started with the following jetting - with the presumption that it would likely be rich (I'm at 5280ft). This was after looking at way too many jetting posts on similar engines. Wax says repeatedly - aim for around a 240 combined count for main and pilot - this is obviously bigger. This is also slightly richer than what factory pipe says for the blaster 2 pipe.

  • Mains: 132.5
  • Pilots: 117.5
  • NS: 1.5
  • Spring: 80gr
  • Popoff (measured): 40psi
  • LSS: 2
  • HSS: 1
I primed the fuel system, hit the primer a few times and it started right up!

Took it to the loading dock, did a quick strap down test and it was idling and moving through the RPMs pretty well - I know by now that neither of these will really tell you how a motor runs while moving in the water though...

Took it out and after a brief no wake zone crawl it was so loaded it wouldn't get on pipe. I hit the beach quick and turned LSS in 1 turn, HSS in .5 turns. BRAAAP. It now runs and can climb in RPMs to hit the pipe. Ran the rest of the 32:1 break in tank through and noticed it does indeed drink fuel. I knew this was going to be the case - so I'm just going to order the slightly oversized Wax tank and get some more volume. Like I said - adventure jet skiing. For those of you that ride dirt bikes with oversized tanks like I do - same idea.

I've since bumped it down to 115 pilot - the 115 pilot is very good and with the LSS set at 2.5 turns out - it's idling like a dream but not loading up. Keep in mind the weird yamaha oem SBNs use the fine threaded low speed screw - so 2.5 turns is like 1.25 regular turns - or something like that I'm imagining. My understanding is that if your less than 1 turn out on the LSS - go down a pilot size so you can fine tune better. If your over 3 turns out, go up, etc.

So for now:
  • Mains: 132.5
  • Pilots: 115
  • NS: 1.5
  • Spring: 80gr
  • Popoff (measured): 40psi
  • LSS: 2.5
  • HSS: 0.5
There's a slight mid RPM flutter/burble and it doesn't climb in RPMs as high as I would imagine it could - both making me think the main is still a little rich. Don't get me wrong - it revs up but I feel like there might be a little more on the table. I gotta do a zero HSS turns test next but I'll likely go for a 130 main next. It really isn't much of an issue as I'm usually not cruising at the exact throttle position to cause the issue, so I can totally live with it. Another rich indications is black plugs with a slight oil left on them. The pistons are also a wet black with no real visible piston wash pattern. It never falls on it's face with a WOT stab and climbs very nice in the RPMs so I'm probably just in-between jets.

I know a lot of guys do the reverse jetting but I'm just trying to get this thing to run good for mid to top fun with enough low end to pull myself out of the hole and recover from a slide out. It's there at this point.

In the end - the power is very strong and linear. I'm very happy with the result given I've never done this type of build before. When sliding/slashing the ski remains hooked up the whole time - sort of like it has more traction now. I'm not sure why this is but It's actually fun and in the last few hours I've been able to really enjoy this new riding style knowing that I can really get slashy and grab throttle and jet off again. There's still enough bottom end that if I'm at least moving a tiny bit I'm going to be able to jump out of the water without issue. Definitely a different powerband vs the 61x cylinder but I'm enjoying every bit of it.
 
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Put another hour on the motor with the following settings:
  • Mains: 132.5
  • Pilots: 115
  • NS: 1.5
  • Spring: 80gr
  • Popoff (measured): 40psi
  • LSS: 2.5 (2-1/2)
  • HSS: 0.125 (1/8)
Got rid of the mid RPM flutter and it pulls much more cleanly up to the moon now without burning up. I'm thinking 130 mains might be good as my riding usually only increases in elevation with the occasional ride at 4000-4500 feet (Grand Junction) and hopefully, yearly trip to Havasu - basically sea level for me. My plugs are still solid black and have a slight oil residue on them as well.

I can always throw these 132.5 mains back in for sea level and it might even benefit from going to the 117.5 pilots as well - but to get my peak performance I think I'll try 130 mains and open it up another half turn on the high speeds to compensate and give me more adjustment for higher elation rides (8000-11,000 feet).
 
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Big Kahuna

Administrator
Location
Tuscaloosa, AL
Awesome update!!!!!!!!! Got an idea, you mentioned the fuel mileage. Why not throw on some OEM 38's? Years ago, Last year I actively competed got to ride competitors (Friends) ski. This was build by Wamiltons, it was a 760 Big Bore like yours with OEM 38's. I was shocked as hell to the hit and power it had. Just a thought!
 
Awesome update!!!!!!!!! Got an idea, you mentioned the fuel mileage. Why not throw on some OEM 38's? Years ago, Last year I actively competed got to ride competitors (Friends) ski. This was build by Wamiltons, it was a 760 Big Bore like yours with OEM 38's. I was shocked as hell to the hit and power it had. Just a thought!

I do have a set of 38s on my other motor I could try. I think I'm going to go the Wax 5.8gal extended tank route to see if it gets me back up to similar range. With the power this combination makes I'd rather just have a bigger tank - it's too fun haha. At my current cranking pressure I can run lower octane gas too which is nice - so 5.8 gallons of cheap gas is pretty much on par with 4.8gal of premium that I was running.
 
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