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  1. #1

    1997 Yamaha Gp1200 Riva Questions

    I have a 97 GP1200 witha Riva Pro series head, and Riva carb plate, independent fuel feed to each carb and it is bored out to 85mm, and is producing 145psi in all 3 cylinders. Also has a ride plate and intake grate, but unsure about anything I cannot see a name on. The motor was supposedly send to and built by RIVA. It is running premix with Yamalube. Also has a primer installed running off one of the main fuel lines.

    It has about 1/2 an hour on a fresh rebuild, melted down 2 pistons last summer, One of the domes was damaged when I took it apart, from a previously gernaded piston from previous owner, as well the mating ring that sits on the cylinder was beat up, presumably from the previous "mechanic". I had a stalling at WOT issue and didn't think anything of it when the engine lost compression, figured I only had a bad head gasket issues that pressurized the cooling chamber (one end of the cooling chamber was black inside the head).

    I have done some searching and haven't found much other then to check/rebuild the carbs and fuel system.

    The ski also has NGK Iridium plugs in it, BR8EIX, which I need to replace now that i Have had it out to break it in.

    So first I am looking for some recommendations:

    1) What plugs should I run in that ski with that set up?

    2) Riva Told me when I ordered the gasket kit for the head that configuration running at 145psi requires 93 octane fuel, which is a problem, I only have access to 91, any recommendations on what to do? Run the 91? stay off WOT? is there a 2-stroke friendly octane booster?

    3)What is a high quality 2-stroke oil to run with that set up?

    Anyone have experience with the WOT stalling? After reading around and having it happen once on the break in runs, I have a feeling that it is a fuel issue, and that is what was the original cause of the engine failure before I rebuilt it. Anything to look for other then replace filters, check vents, dismantle carbs?

  2. #2
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    Pretty easy. A WOT stall means its lean and seizing. Which means the carbs aren't jetted properly or they is some other restriction (or air bubbles) in the fuel system. And that restriction would be the primer kit installed on the fuel feed. The tee fittings have a smaller ID and cause a restriction. Or if they are a full sized ID, the fuel system can suck air bubbles through the primer.
    So move the primer to the return line. Or install a full size ID tee and a check valve to prevent a fuel restriction and air bubbles.

    The other concern I have is going WOT on such a fresh rebuild. Most people recommend not going over 3/4 for the first tank full which could take 2 to 4 hours of run time. A meltdown in the first 1/2 hour means you're hammering on it too early, IMHO.

    91 octane is fine.

    There are lots of high quality 2 stroke PWC oils out there. I run Amsoil. Some people say there are better oils, but nobody says Amsoil is a bad oil. Start searching through the RECENT oil threads, read people's advice, and decide for yourself what oil you want. All the "high" quality oils will work just fine for you.

  3. #3
    Awesome, Thanks for the advice. I am going to go over the fuel system and put in new filters, and check the carbs to make sure they aren't gummed up. I have been just tooling around on calm water at all different speeds, and did one stint of wot and it stalled and that was the end of the 2 nights of 20 mins each. I will keep it dialed back a bit longer though.

    Any recommendations on plugs?

  4. #4
    Yamaha artisan Cutlass's Avatar
    Join Date
    Oct 2010
    Madison, WI, USA
    I think most people just use the stock plugs

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