The X4 Thread

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Stunnerable said:
Are you planning on doing any racing? For fun?

The engine needs to be 100% to even consider any power mods so I'm not going to even talk about that.

As for handling, get some 3 degree trim tabs, worx or JD #6 grate, and a good set of sponsons. Thing will turn on a dime. Then you can think about maybe a swirl impeller for bottom end and maybe a steering system which does wonders to the feel depending on who you ask. Obvious mods like mats and a sticky seat cover can be done relatively easily. If you REALLY want to get serious have your hull trued and blueprinted. It actually does make a difference but now we are getting into actual racing mods.

Some of the mods mentioned can be tweaked for the conditions you ride in. Flat vs rough water, etc.


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Cool, so I already have the Beach House sponsons, I would love the steering but I can't believe how much it is! I'm thinking the JD grate and maybe do up the carbs then tune it real nice. I ordered TTO tach and under plug temp gauge, that should allow me to get it dialed pretty good. I figure remove the chokes, and install a primer kit and the ocean pro flame arrestors I got with the boat. What do you think? I figure I better get it running its best stock before putting much on it. The Engine seems real solid, 150# on both cylinders checked cold. I think it'll take a little bit of modding. If I get it running good and want more I was thinking a good but mild pipe would be a Rossier, I found one I think I can get pretty cheap.. What do you think?
 
As far as pipes go, you'll find several opinions but one constant is that no pipe works as well as a factory pipe. No other pipe is even worth it as far as I'm concerned. Spec 2 has more potential but requires a pretty good level of tuning skill to run on pump gas. Spec 1 gives really good gains and is more "forgiving" to the lower octane operation but seriously, you better know what your doing setting up the motor or you'll hate your life.

A properly set up piped 787 feels like a huge jump in power. But you have to get it right. The reason I said your engine needs to be 100% is because when you start modding one of these any weak link is going to rear its head and very quickly.

Remember, modding skis is a domino effect. If you change one thing, something else most likely needs to be upgraded or tuned. Well, if you want to do it right at least.


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Oh yes, believe me I know all about "the mod chain" lol! I mostly was looking for SeaDoo specific things, I have quite a bit of tuning experience, I raced a FULLY modded, Stroked, MRD fuel injected, ported to the hilt, piped Kawaski 750 standup so I know the basics. It sounds like the Doos are pretty much the same animal. I wasn't sure if my sponsons were good ones, and I've been out of the game for a long time so I'm sure I'll be rusty, lol! Like I had no idea they had impellors with the swirl design!
 
Pipe with electronics, milled head, and flame arrestors with rejected carbs are a great place to start...if you can swing carbs too even better.

At this point the aftermarket parts are only going to increase in value unless people quit riding xps... Which I never see happening.

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Haha! I hope people never stop riding them Nick! Greatest ski ever made as far as I'm concerned. Blaster is a very VERY close second. (Sit downs only) Greatest "ski" would have to be the original JS. Got the whole ball rolling.

Whiplash, please forgive my seeming distrust in your mechanical know how. Hell for all my know you could teach Bill O a thing or two. It's just being in this sport for so many years I've seen sooooo many horror stories from people modding skis. But man, if you get it right.. freaking awesome ski it can be!


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Yep.. I know the Neptune dry pipe very well. I remember how much success Bo had using that pipe. I almost bought one from him back in 98. Those things are rare as hens teeth now, at least near me.


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It was heavy tho! After 20 yrs of tweaking these x4 boats the best bang for the buck is the 951 swap. These stock mtrs pull nearly as hard as full built limited and outrun them by at least 4mph safely in pump gas all day long. Maintaining a 7400rpm 787 mtr is overwhelming for a rec rider. No replacement for displacement! Imhop
 
Any links to decent build threads for the 951 swap in our hulls?

Oh here's today's major HP injection! Lol.
 

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It'll look better with the sweeping point to the nose just below it and the aftermarket bars coming soon.. Also I'll be removing most of the stock decals soon too..
 
Whiplash said:
It'll look better with the sweeping point to the nose just below it and the aftermarket bars coming soon.. Also I'll be removing most of the stock decals soon too..
Click to expand...



Those decals look mint, The colors are still really vivid and I do not see any tears. I have a hard time peeling off good graphics now. I use to be a strip the decals guy until I realized the resale value is more when the decals are left on. Do not get me wrong I will still strip them if they are faded or torn but those are perfect.
 
Now we're talking! A properly set up 951 can push over 170hp on pump gas. You're talking extreme acceleration and over 70mph on top.

Start a thread! lol


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Maybe after this season if I can find a good doner engine. That sounds like the best possible setup for sure! Even if only mildly built, I think 150ish horse is likely obtainable reliably with an engine like that no? That's only a 20hp gain really over stock?!!
 
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Riding a 951 X4 is like riding a CRF450 dirt bike. Super torque even at high speed. 787 mod can be bit more snappy on throttle response. Running these hulls in 70mph range takes big ballz of steel. (:
 
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