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  1. #1

    1990 waverunner III 650

    whats up everyone, im new to the site.

    so i just bought a 1990 650 and my question is what can i do to get some more performance and power out of it?

    i already blew the engine so i have a cylinder exchange kit on the way with new heads.

  2. #2
    This is how I run a jetski shop in the desert nmpeter's Avatar
    Join Date
    May 2008
    Elephant Butte New Mexico
    my stock answer to this question( which I get almost every day at the shop)

    "you can see immediate performance and health gains by dropping 20-50 pounds" too!

    Trying to squeeze more power out of a 20 year old engine is a questionable endevor.

    Oh yeah..welcome to GH

  3. #3
    thanks, but wouldnt a new pipe or carb do somethin?

  4. #4
    cmgww's Avatar
    Join Date
    Jun 2010
    Indianapolis, IN
    How much you want to spend? In the mid 90s we had a 1990 WR3 that was modded by GroupK, 685 kit, Riva pipe (the old red one), 180 psi...That thing went 53 mph! Probably the fastest WR3 of all time if not close. However, this was before my dad was really experienced with Yamaha 2 stroke engines and we quickly realized that 180psi is was too high for pump gas. We blew that engine sky high later that summer. We re-did the heads, backed off the compression and it ran pretty great, would beat Sea Doo XPs, Raiders, etc out of the hole (big pump)...It was a blast!

    Anyway, I suggest you ship that cylinder kit out to GroupK the minute you get it, have them do the 685 kit (you can't bore a 633cc engine out to a 701 b/c the cylinder walls would be too thin, so they bore it to 685). In addition they have a couple other kits that will give you a nice boost in performance. They will mill the stock heads for more compression, port the intake/exhaust, etc... Of course it won't run with today's machines, but it would be enough to be fun and faster (maybe 45 mph or better, stock was around 35 mph)

    We've had a lot of good results from the guys at GroupK...and they still work on the older engines so you are in luck there.

    here's a link for your particular engine, they have a ton of great information on their site, esp. for the older skis...

  5. #5
    cmgww's Avatar
    Join Date
    Jun 2010
    Indianapolis, IN
    You can leave the engine stock and just put a pipe on, not too sure that any of them make pipes for the 650 engine anymore...well pro-tec does last i checked

    these guys make a great pipe that I have on my super jet. Plus they sell the 650 manifold so you can bolt it right on. you can't put a 701 pipe on a 650 b/c the exhaust ports are different sizes, if I recall correctly

    these guys have a WR3 pipe but it's for the 701 and see if they still make the 650 manifold...

    hope that helps

  6. #6
    cool thanks i'll have to check all this stuff out

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