640 cuda/race build
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  1. #1
    PWCToday Regular daltonace's Avatar
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    640 cuda/race build

    custom cuda build
    modified pump 140mm to 146mm mod
    built 640 look for any old racing mods for 640 LOOK FOR a 7500 rpm box group k references
    some port work
    milled head off set fly wheel key going to lighten the fly wheel 185psi compression going to run 95 Daytona pipe and carbs
    black magic intake grate and ride plate

    I built this cuda with stock pump and modified motor got 2 years out of it then i twisted a crank so was going to put a 770 in when through my part collection i got enough parts for 3 complete 640 motors and some spare top ends past that so i decided to push my 640 harder since i cant mange to sell them to buy a new 770 crank and top end I will post my build as i go look for any 640 build info i dug around here forever got the big things covered look for any that push a 640 hard as it can go not above running race fuel have in the past I know what i have 640 is what it is one day i will go bigger motor down the road.IMG_20180502_184051.jpgIMG_20180502_184101.jpgIMG_20180502_184107.jpg

  2. #2
    PWCToday Regular daltonace's Avatar
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    Re: 640 cuda/race build

    pump build not installed yet half 1994 dead pump no oil ran until trashed by former owner and 97 Daytona pump IMG_20200201_190005[1].jpg
    Attached Images Attached Images
    Last edited by daltonace; 02-10-2020 at 10:12 PM.

  3. #3
    PWCToday Regular daltonace's Avatar
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    Re: 640 cuda/race build

    Last edited by daltonace; 02-10-2020 at 10:18 PM.

  4. #4
    PWCToday Regular daltonace's Avatar
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    Re: 640 cuda/race build


  5. #5
    PWCToday Guru GustoGuy's Avatar
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    Re: 640 cuda/race build

    Another mod I did was clean up the exhaust ports to remove some of the roughcasting and I also cleaned up the exhaust manifold with a fine sandpaper ball and polishing ball and and some polishing compound and I got it really smooth. Seems to help a little bit. A friend of mine has an old Kawasaki 750 and my 1999 modified TS640 absolutely kills his of the start and runs away from him. Fett Brothers sells flywheel advance keys which will fit your engine I bought one and it helps a bit plus at high rpms the CDI box tends to back off the advancement anyway so it will help a bit. Make sure to hog out the engine blocks water intake fitting a little bit since the engine will run hotter with advanced timing and more water flow will keep you safer. Basically the machine is really old and I would not spend lots of money other than some inexpensive fun mods to make it a little more enjoyable to ride.
    1999 TS 640
    Mods include Prok multifit with aluminum adapter
    Mukuni primer kit, 6 vein stainless steel delux Tigershark
    Jumbo Pump with 12/18 Polaris Skat Trak impeller from Impros. Group K flywheel mod (-0.7lbs) removed. Group-K Cylinder head mod milled for 91 octane 180psi compression, Group-K intake manifold mod, Lubrication: Amsoil Interceptor nonoxgenated 91 octane gasoline. Fett Brother 1.4 degree offset flywheel key.

  6. #6
    PWCToday Regular daltonace's Avatar
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    Re: 640 cuda/race build

    i have 8 jugs and 4 good cranks laying around so im just clean up my 640 motors had one other 640 that out run 96 daytona 770 i had no luck selling the stuff so im just going to push ever one until i kill them or run out of parts then putting in probably a 720 seadoo or 700 polaris just can find the info i want

  7. #7
    PWCToday Newbie YAMAHA 5000's Avatar
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    Re: 640 cuda/race build

    What do you think was the bottom line of performance improvement?

    How did you connect dual carbs to the PJ640?
    Did you also install dual tuned exhaust pipes?
    Do you have access to another Group K RPM Box?

  8. #8
    PWCToday Guru GustoGuy's Avatar
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    Re: 640 cuda/race build

    Since you have an older Tigershark I am not sure if you will be able to find any upgraded impellers. I have an Impros Polaris Stainless steel 12/18 Skat Trak impeller and the 6 veins stainless steel pump off a 770 Tigershark and it made a noticeable difference in the holeshot. But this was years ago and right now Tigershark parts are 20+ years old and much harder to find than when they were 10+ years ago when I upgraded my machine.

    Cheap proven engine upgrades are to mill head for 175 PSI compression. Lightened Flywheel for greater acceleration and an offset flywheel key for some advancement in the timing which will help the engine to produce a bit more horsepower. Make sure to enlarge the intake for the pump water cooling to the engine off the pump and where the fitting goes into the engine to allow for better water flow through the engine to keep temps down with the flywheel offset key. The higher RPM ignigtion module would also be a nice upgrade if you can find one. Another thing you can do is swap the 640 cc engine for a larger 770 engine and that would be a huge 10+ hp upgrade in power.
    Last edited by GustoGuy; 05-30-2020 at 04:54 PM.
    1999 TS 640
    Mods include Prok multifit with aluminum adapter
    Mukuni primer kit, 6 vein stainless steel delux Tigershark
    Jumbo Pump with 12/18 Polaris Skat Trak impeller from Impros. Group K flywheel mod (-0.7lbs) removed. Group-K Cylinder head mod milled for 91 octane 180psi compression, Group-K intake manifold mod, Lubrication: Amsoil Interceptor nonoxgenated 91 octane gasoline. Fett Brother 1.4 degree offset flywheel key.

  9. #9
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 640 cuda/race build

    Any chance one of you guys has the low performane stainless 640 exhaust around.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  10. #10
    PWCToday Guru GustoGuy's Avatar
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    Re: 640 cuda/race build

    Actually Group K tested both exhaust systems and found no significant difference between the two in horsepower. One area to improve the 640 is to clean up the casting flash in the exhaust ports and to smooth out the exhaust manifold and polish it on the inside with a foam ball mag wheel cleaner and some rubbing compound until its smooth as can be. I also smoothed out the welds in the stainless steel exhaust pipe and smoothed it out on the top of the pipe and the flange were it enters the water box. As to aftermarket water boxes they are just too expensive and tend to be much louder than stock and at best give an additional 1to 2hp at most.
    1999 TS 640
    Mods include Prok multifit with aluminum adapter
    Mukuni primer kit, 6 vein stainless steel delux Tigershark
    Jumbo Pump with 12/18 Polaris Skat Trak impeller from Impros. Group K flywheel mod (-0.7lbs) removed. Group-K Cylinder head mod milled for 91 octane 180psi compression, Group-K intake manifold mod, Lubrication: Amsoil Interceptor nonoxgenated 91 octane gasoline. Fett Brother 1.4 degree offset flywheel key.

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