New Owner 1986 Kawasaki JS300-B1 . Hello!
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Results 1 to 5 of 5
  1. #1
    PWCToday Regular Pb300's Avatar
    Join Date
    Mar 2018
    Location
    East Side Michigan
    Age
    25
    Posts
    110

    New Owner 1986 Kawasaki JS300-B1 . Hello!

    Greetings from the southeast side of Michigan. I recently fulfilled my wish to obtain a stand up. I found a local 1986 JS300-B1 for $150 bucks. I have read through "The Official JS300 - 300SX Bible" but there are some things that are still a little unclear to me or that I missed. I do go back to the bible to try to answer my questions so forgive me if I missed something. That is a very knowledgeable threat and I appreciate that it exists.

    So I purchased that JS300. I am still on a student loan budget but I am happy to spend some time to work on it and put some money into that for now. I checked it out before I purchased it and everything seemed to be in proper order. The psi was around 145 psi but it had a weak spark which eventually appeared to be inconsistent too after I purchased it and began diagnosing it. I did rebuild the carburetor for good measure. I bought a used set of electrical box components and I am hoping that it is just the igniter coil that is bad. I will test it out this weekend. I hope everything else is in working order. If so, I plan to replace some fuel lines and take it for a spin the on the river to make sure everything else is functioning properly, then I will begin some cosmetic stuff. I have a Js300-B1 service manual so if you have any inquires I will try to answer them. I also have a .pdf version of the 1988 Js300-B3 owner's manual.

    From my understanding and thread 'research', it seems that the JS300 and 300sx engines are the same. They used the same engine in the JS300 as in the 300sx, but there is a difference in some other components such as the shaft coupler, exhaust, and the mounts, maybe something else too. The JS300, JS440, and JS550 have the same hulls, right? Or is the 650/440 conversion I've read about refer to putting a 650 into a 440 hull which is an sx hull? I am honestly a little confused on the hull designs and nomenclature.


    Other notes:

    I found a 1990 300sx for cheap that is also local. Cosmetically it looks good and I will be taking a look at that in person. Since the JS300 and 300sx have the same engine, I should be able to interchange and swap components such as the electrical boxes for each engine. Which could be a good thing. I just have to make sure they both run and if not I have other spare parts to sell or keep.


    I found a Kawasaki 650 engine for cheap. I do not know which year. Not sure if it works but I will check that out this weekend to make sure the pistons and the case are clean and that it is not seized. It has been removed from the hull. It still has the carburetor and muffler attached so I hope those have helped keep matter out of the engine. It comes with the coupler and I believe the pump as well. I am thinking about scooping that up for future iterations of my JS300 or 300sx if that is possible.

    I have read about JS300 conversions to 440 and 550, but not much on 650. Does anyone know for certain whether a JS300 hull or a 300sx hull can be fitted with a 650 and the proper brackets? If both, which would be best considering both operate just fine?

    Is the 650sx hull the same as the 300sx hull?

    Any help is appreciated! Thank you.

  2. #2
    PWCToday Guru
    Join Date
    Mar 2003
    Location
    Shiocton, Wisconsin
    Age
    41
    Posts
    487

    Re: New Owner 1986 Kawasaki JS300-B1 . Hello!

    Hi, the JS300 shares the same hull designe as the 440/550. The JS300 uses a 440 pump. The 550 uses a different style pump. I'm pretty sure the 1990-1995 550 pumps are different
    than the previous model 550 pumps also.

    The 300SX is a hull all its own, it is not the same as the JS300/440/550 or the 650SX. The 300SX
    uses a 440 style pump.

    The JS300 and the 300SX share similar engine components. I know the engine mounts are different, the starter shaft and starter idler gear are different, and I think the drive coupler
    length is different.

    Yes, you can install a 650 engine into a JS300. You will need 440/550 motor mounts, a 440/550 engine bed plate and a conversion adapter plate, not to mention the 650 electronics, a properly pitched impeller, a modified 440/550 drive coupler to fit the 650 output shaft and
    there will be other items that need to be custom made along with some fab work. It's not
    an extremely hard swap, but to do it right it won't be cheap or free. Its definitely not a bolt in and ride project.

    Installing a 650 into a 300SX will require more custom work since the 440/550 engine mount plate will not work, and the waterbox is located at the rear of the engine compartment.

    Another thing to consider is the over-all condition of all
    of the jet-skis/engines in question. Good cranking compression numbers
    are just the start. All of these 30 year old skis are ready for new crank seals, a very
    important aspect of a properly tuned and running engine.
    Last edited by ACP; 03-24-2018 at 02:34 PM.
    2001 Superjet; R&D, Blowsion, UMI, Riva, Wetwolf, Ocean Pro.

    1987 650sx: Mariner, UMI, Neo Designes, R&D, Jetsports, Renthal, Hydro-Turf, Skat-Trak, Reworked stock pipe, 40mm carb, Wetwolf F/S cone.

    1986 JS300; lots of mods, fast for a 300...I think

    1987 X2: Rips pretty good and has some 80's flare.

  3. #3
    PWCToday Regular Pb300's Avatar
    Join Date
    Mar 2018
    Location
    East Side Michigan
    Age
    25
    Posts
    110

    Re: New Owner 1986 Kawasaki JS300-B1 . Hello!

    Thanks for the info. Not planning on doing a 650 conversion for a while. I need to enjoy this 300 first (once I get it running).

  4. #4
    PWCToday.com Is My Home Away From Home john zigler's Avatar
    Join Date
    Mar 2003
    Location
    wisconsin
    Age
    51
    Posts
    8,247

    Re: New Owner 1986 Kawasaki JS300-B1 . Hello!

    Welcome to the addiction....
    RCJS also doing business as WATCON
    608-743-1305 9am to 5pm CST m-f
    email watcon@watcon.com

    Please visit our web sites

    new parts / products / services www.watcon.com
    used parts www.rockcountyjetski.webs.com
    thank you

    Please check out and like WATCON on Facebook

  5. #5
    PWCToday Regular Pb300's Avatar
    Join Date
    Mar 2018
    Location
    East Side Michigan
    Age
    25
    Posts
    110

    Re: New Owner 1986 Kawasaki JS300-B1 . Hello!

    Thank you!

    I've come across a 1996 Kawasaki 750ss with a pump on it. Would it be worth my while to strap my 650 engine in there for the time being? I am thinking I could use the 750 pump later if I ever do the conversion of the 300 hull too.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0