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  1. #1

    2019 RXT-X 300 Mod recommendations.

    I want to pre-req this with a request that we stay on topic of mod/gains and stay out of the weeds.
    I don't want this to derail into posts arguing about Speedo vs GPS and/or how air/water temps in one place are better than the other.
    I also don't want this to spread into other platforms and what worked there and why.
    I am trying to really hone in on what will work for this specific engine/ski combo and what is realistically possible.
    That being said I also know that there are a LOT of variables involved so I will try to provide as much information as possible.
    If anything is left you please prompt what information you would need and I will provide what I can.

    Current Locations is Long Island NY.
    Average Air temps: (according to google)
    Highs: Jun 79, Jul 84, Aug 83, Sept 77
    Lows: Jun 60, Jul 67, Aug 66, Sept 66
    Average Water Temps: (according to google)
    Highs: 75
    Lows: 70
    These temps are rough based on googling info... It's south shore long island.

    My current baseline is this:
    2019 RXT-X 300 -
    Only Mod currently is a SCOM installed.

    Bone stock, after she opened up a few hours into breakin, I would hit 72 on the dash in bursts, and settle down to the 68-69-70 flutter due to the SCM.
    After putting in the SCOM, On this mod alone I have seen up to 79 on the dash, and have hit it pretty reliably in flat water.

    It's been a lot of fun beating on my pal who has a GP1800R as hole-shot we are neck and neck, but hitting late 60's and beyond I just walk away like it's nothing.
    This year he is putting in a Stage 2+ kit from Riva to compensate and of course, I want to keep the pressure on...

    I do not want to get crazy here, but I would love to push into the mid 80's if possible.
    I also want to do what I need to in terms of protecting my investment.
    There are so many mixed messages around every single mod, It's exhausting trying to figure out who is right and who is wrong.
    I hope that on this thread people can offer up actual numbers, or pictures or first hand experience to help me sort though the muddy waters.

    What I have been considering is the following:

    Intake: Likely going with RIVA Power Filter setup because of fit/finish and it looks clean. I do not want to use the DIY style versions but if anyone knows any others that are as clean as a setup or that are better for some reason please chime in.

    Exhaust: Likely going with RIVA Rear Exhaust here as well because of lack of options. I know that this does very little for power but I also dig the sound.

    Upgraded Inter-cooler setup: (Looking for more info here) but thinking Fizzle SuperCooler + Tubing upgrade. One thing that is hotly debated is BOV vs no BOV... I have heard strong arguments on both sides and still don't know what is better. Is anyone running one way or the other? Or did run one and have issues? From what I understand if your running stock boost it's not needed.

    Water box: I don't really know much about this but seen them at the RIVA site, can anyone give some information on this? Not much out there on them being worth while?

    Intake Manifold Girdle: Precautionary? Is it worth the investment?

    Intake Manifold Upgrade Kit: RIVA's kit seems to add 1lb to boost if I understand this correctly... This seems like a great mod for the $

    Fuel Pressure Regulator: RIVA has the Rising Rate Fuel Pressure Regulator Kit, I am assuming this is only needed if your pushing up a good bit more boost?

    Catch Can/Breather: RIVA makes one, so do many others... Not sure if any of them are "better" than others but assuming after all even if it does very little, it's better than not having one?

    Impeller: The right spinnymabob for the job... Seems like Solas had a run of them that blew up and pissed everyone off, but now the SXX's are beefier? I also have heard people staying STICK WITH STOCK on the prop... I honestly don't understand the mechanics of it, and I don't want to manually be pitching an impeller. So I am hoping that there is a clear "this one" or "none" answer here.

    Lucky 13 Cones: This is likely the one part that escapes me on what it is, how it works, why anyone uses it and how the adjustments change anything. If anyone wants to explain that would be great.

    I realize this is a lot of requested information, and that some of this might seem like spoon feeding but honestly I have been poking around and trying to find clear answers and for this particular ski there isn't too much information that is concise. I am hoping I can learn more in one consolidated thread and that others can use this as a good knowledge pool as well.

    Lastly if anyone knows a good shop on LI or in NY/NJ I would love to speak with them as well.

    Thanks everyone for any help in advance, I really appreciate the sharing of information and hope my request to stay tight on topic doesn't make me seem like an uptight ass.

  2. #2
    prowler1k's Avatar
    Join Date
    May 2013
    Grand Lake, OK
    Mid 80's?
    It gets pretty spendy to make that happen.

    If you want to hit that number I would suggest a 142 wheel/injectors/tune and prop accordingly. If you want to do the cone, it sounds like people do get positive results but it requires a fair bit of patience to dial it in.

    Fizzle pipes and upgraded intercooler are on my to do list, and will help, but less so in your environment.

    Get more air into your hull (search) and that will help.

  3. #3
    Luck13 cone, intake manifold girdle, and fuel pressure regulator aren't really needed at that level either. Better off getting some springs and retainers. I doubt you'll see what you want without a supercharger upgrade though, but the 142 isn't needed for mid 80s. Probably a 135 wheel with injectors. But if you want mid 80s, you definitely want at least retainers at that point. Things start to get hairy for valve float above 8300-8400.

  4. #4
    You didn't mention a reflash (unless I missed it). Are you considering one? 79 mph, with just a SCOM, is excellent.

  5. +1 by:

  6. #5
    Bob 1tommygunner1927's Avatar
    Join Date
    Apr 2007
    Houston, Texas
    Buy a shop manual (brpmanuals)!

    Before doing any mods, my suggestion is to first check the alignment of the pumpshoe to the thur hull fitting to the engine. You will need all the proper tools to ensure proper alignment. The alignment also affects the alignment of the ride plate and in turn affects the intake grate alignment.

    Doing the above will enhance longer lasting carbon seal and get the most out of the mods you listed above.

  7. #6
    Subbed.. Just bought a 2019 RXTX 300 and looking for the same answers. Really just wanting better sound from exhaust and reliability. Looking to do some Hull Vents with frogzskin, Catch can, 3'' silicone intake elbow with K&N filter and pre filter, and DIY free flow exhaust kit, and Speed control module from RIVA. Hoping to see 75 - 80 MPH and just n all around dependable bike.

  8. #7

    Join Date
    Jun 2017
    Lake Lanier, GA
    I'm going all out with mine (, maybe at a slightly slower pace, but everyone's welcome to follow along

    I'd really like to see 90, but it doesn't seem likely without race gas which I'm not willing to do. Make sure you do the valve retainer upgrade at least for higher RPMs and the flywheel bolts. Those are mainly why I'm taking the slower approach - don't want to pull my engine out before I can ride this summer.

  9. #8
    Quote Originally Posted by Krystofer View Post
    Subbed.. Just bought a 2019 RXTX 300 and looking for the same answers. Really just wanting better sound from exhaust and reliability. Looking to do some Hull Vents with frogzskin, Catch can, 3'' silicone intake elbow with K&N filter and pre filter, and DIY free flow exhaust kit, and Speed control module from RIVA. Hoping to see 75 - 80 MPH and just n all around dependable bike.
    I would get the 4 inch RIVA velocity stack adapter and go 4 inch since you want to go the elbow route anyway.

  10. #9
    I went that route, but another option is a 4" to 3" elbow and just eliminate the stack adapter. Less parts, less cost.

  11. #10
    Do u have a pic. Can’t find anything on that

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