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  1. #1
    Highlifeking's Avatar
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    Riva head and Flat Top piston question

    I have a fully ported Tim Judge 1200r engine that was setup for tripple pipes with 175 PSI, Im wanting to convert to single pipe rec use. It has a Riva Pro series head with girdle kit and is using ART flat top pistons with a 50 on top, which meens its .50 overbore right? Im wanting to get the compresson down to 155psi so i can run 93 octane fuel, I plan on switching heads to a ADA set i have which are making 155 on stock pistons. Can i use these flat top pistons with a regular head like this? I know this Riva head is ment to run with flat top pistons but im wondering if i can keep these pistons, or will i have to get new regular pistons? The flat tops would change the compression and squish maybe? Any thoughts, Thanks


  2. #2
    88kawi5fiddy's Avatar
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    The flat tops make way more power and it will run funny with a non flat head with flat tops. The huge squish band would promote power loss and probably induce detonation.

    The best option IMO would be to contact a builder that does machining and get the current dome volume increased to run the way you plan. Only problem is once they are machined bigger, those heads won't ever be able to run the pipes or compression that TJ set em up for

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  4. #3
    Prism's Avatar
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    The porting is set for the triple pipe RPM range as well. If the compression concern were to be addressed, the porting is not optimized for the single pipe set up. You might be able to sell the setup you have for enough to buy a good used stock or single pipe ported set up. This race fuel triple pipe very high end 2 stroke stuff is getting tougher to sell imho though.

  5. #4
    88kawi5fiddy's Avatar
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    I would trade you, but then I would have to run open class and I wouldn't wanna run open class, or buy race fuel for two boats. Have to have a huge budget to run a boat like that just for fun.

  6. #5
    Highlifeking's Avatar
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    Ive talked to TJ and he said i need to keep the flat top pistons, I plan on using an ADA head and he recommended i send my old Riva dome to ADA so they could match it and get the compression down for Pump fuel 93- around 155psi- ADA will make me three new domes for this setup.

  7. #6
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    Can you drop the compression and keep the triples? That would still be a lot of fun.

  8. #7
    Highlifeking's Avatar
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    My buddy got this engine for cheap to replace his old blow engine- Were doing a rec. build with single pipe, vf3's, protec ignition, 155 compression and HO pump. I understand it was ported for a particular setup, but were going to use it for recreational purposes and see what it can do. The guy we bought if from said a single pipe was fine, and TJ just recommended that i use the flat top pistons with the proper domes-

  9. #8
    Mpeavler's Avatar
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    I had a 155psi TJ built flat top...single pipe.....dam it ripped !! The downfall to mine was even at 150 PSI ...I had to run Race fuel to keep it from blowing up.

  10. #9
    Highlifeking's Avatar
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    How did you know it needed race fuel? And was the engine built for the single pipe?

  11. #10
    Mpeavler's Avatar
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    Yes it was build for a single pipe from day one... the porting was just too hot to run pump fuel on....I had Detno and killed the pistons x 2 before I narrowed it down....and figured it out. I was running both a Riva CDI at the time and thought the timing curve was too tall for it . I went to stock ECU...fried a second time and finally running 110 in it....it lived for another 50 hours before I sold it. It sent my Raider to over 70mph .....and got there in a dam hurry. It was a wicked set up. When I got it ...

    TJ ported Cylinder
    TJ expox cases
    TJ true/welded crank
    I added:
    VF's 3's
    46 Mukuni's
    Riva CDI
    150 PSI head and 175 PSI ADA girdled head
    Pro-tec port matched intake

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