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  1. #11
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 657 vs. 657x engine comparison

    They did turn out looking pretty clean after everything was installed.





    Rotary valve on the 657 was 147 degrees.
    On tthe 657x it was 159 degrees.
    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

  2. #12
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 657 vs. 657x engine comparison

    Something else I thought of.......I've never seen a single carb 657x. So I'm betting if it's all original single carb it's a standard 657.
    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

  3. #13
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 657 vs. 657x engine comparison

    No 657 ever came with single carb,they were all duals.

  4. #14
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 657 vs. 657x engine comparison

    Well there ya go! For some reason I was thinking the SPI was available with 657 lol.
    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

  5. #15
    PWCToday.com Is My Home Away From Home Mr. Bill's Avatar
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    Re: 657 vs. 657x engine comparison

    WOW! I built a show and go XP for a guy in 1993. It was featured on two pages , the center fold, of a Splash Magizine.
    IT had the exact same colored cases, and the same color of purple on the exhaust manifold and polished then chromed complete oem pipe. The head was first polished, then chromed, then powder coated green with the Rotax and other raised features of the head shell still in chrome. All colors on the motor were powder coated and the paint used was some very expensive and durable chip resistant military grade paint.
    The hull was a ligther colored green with tiny flakes in it, many coats of clear over it. It had all handmade matching mats and seat cover, with UMI polished steering, bars and switch holders. It had WATERCRAFT MAGIC hand painted in a contrasting color on the hull sides below the bumpers in bold letters as big as the large Sea Doo decals used on the side of some oem hulls. They were painted on and color sanded along with the rest of the paint before clear coating went on. The paint job for the hull, deck, and engine cost well over $2500.00, not counting polishing, powder coating costs and chroming.

    The jetpump was also purple with chrome nozzels. I still have a few pieces of that motor on my shelf as I eventually ended up with the engine and pipe years later.

    If there is a 1mm difference in the two clyinders hieghts, you are mixed up about something. The pistons in the 1993 motor came to the top of the bores, thus the recessed squish bands in '93 heads. the '94 motor, the X, had pistons lowered by 1mm in the bores, and no cut into the chamber squish bands to even out the compression ratio of the two 657 motors.

    Also, do not tell people that you can use a 657X head to raise compression on any non X 657. It will only last minutes in an engine with piston crowns at the very top of the bores before it melts the aluminum on the piston crown and if run lng enough, either blow a hole in the center of the piston, or detonate the rings and edges of the piston crowns so badly that they break off. It will for sure overheat and sieze. You cannot run a two stroke motor without minimum squish clearances for the quality and octane fuel that is being run through it.

    And like Dan pointed out, you got your X crank mixed up with your 657 crank if both came from the correct model years of XP's, 1993 and 1994.
    In an effort to make a lighter full circle crank, Rotax needed to put large holes in the counterbalancer full circle weights, and make them thin and light as possible while still maintaing some reasonable amount of harmonics in the engine so it would not crack the engine cases, rotary valve surfaces above the top case, and shatter the intake manifolds. In doing so, the 1993 657 crankshafts were weaked to the point when they got hot from hard running, and were put under the shocking stresses of an impellor losing and regaining bite as the hull was sometimes in the air and other times in the water, it would twist the crankshafts in a heartbeat. I never checked index on a used 1993 crank without finding it way out of spec, sometimes twisted a quarter of the way around. Because the counterblancer flywheels on the '93 crankshafts were made the way they made them, the pins in them would loosen in their holes as the crankshaft flywheels expanded with heat. One good yank on the impeller would twist a crankshaft out of index. Imagine the twist on a driveline and crankshaft when an XP came down from jumping a wave with the rider still pinned on the throttle to rev limiter hieghts. That was the cheezeist crank that Rotax ever put into a Sea Doo hull. Good idea, bad results.

    If you closely inspect the two PTO's, they are quite different too. One is heavier than the other. And that effects the absorbtion of engine harmonics, a terrible problem for a two clyinder motor. Seems to me, the 1994 PTO was shaped much differently than the two in your pictures. It was shaped more like the 720 pto. with the majority of the weight further away from the centerline of the crankshaft which is a big factor in torque production.

    The cases are different for other reasons, mainly to make X cases stronger. The thickness of the aluminum in most all areas is thicker. When we were cutting cases for 4mm stroker cranks to fit into them, we had to add alot of aluminum to the lower part of the cases right at the bottom of the cases, by welding layers of aluminum onto the bottom of the cases, before we flycut the cases to clear the longer stroked crankshafts in 1993 cases. But no extra aluminum is needed in 1994 cases, until we tried as much as 8mm strokers...........
    The area right where the rotary valve surface is above the upper case half, if you look at the two closely, you will notice reinforcment webs supporting that thin aluminum rotary surface above the cases where 1993 cases allways crack but not on 1994 X cases.

    The two intake manifolds have totally different stud alignment as they are inline with short studs on a 1993 inatake manifold, and non existant studs, and replaced with threaded holes that are both angled on the manifold and not inline with each other at all. I series carbs use long hex bolts to hold the carbs on. '93's use nuts on studs that are frustrating and difficult to remove or even access with conventional SBN carb flanges on inline shaft to shaft carb sets.

    They probably eliminated the case drain plugs because nobody ever really used them. They are extremely difficut to access when that motor is in a Sea Doo hull. Kinda like the drain plug in a 787 case, it is accessable if you know it is there, and not in an XP model, but a screw-in cap above the counterbalance drive gear is so much easier to remove and then suck the water out.

    The two motors share only a few parts that were not changed. the head cover, the rods are the same specs I believe. I am not even sure if the bearings on the crank were exactly the same spec, but they are interchangeable on either crank. I think the 1994 bedplate may even be stronger, not sure though. I believe they used the same oil pumps on both motors. And maybe the woodruff keys in the crank snouts. Pistons fit either motor.

    I am sure I forgot more than I remember.
    Last edited by Mr. Bill; 03-09-2010 at 07:42 PM.

  6. #16
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 657 vs. 657x engine comparison

    Great! Lots of good info Mr. Bill. As I stated earlier this information was from my personal observation. I machined .039" off the bottom of a 657 cylinder and put it on a 657X It ran great.

    ATTENTION: TAKE MR. BILL'S ADVICE ABOUT THE HEADS!!

    He knows more about it than me. It's been a while since I've done that project. I must be mixed up about the heads.Or maybe the cylinders.Got the two confused.
    Obviously the intake bolt pattern are arranged different to accept the I series carbs. Apparently my brain siezed up. But the intake openings and volume seemed to be the same. PTO's might be different in the XP. These two I did were from a '94 and '95 GTX. I probably should have noted that in the first post.
    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

  7. #17
    PWCToday Guru rupertmja's Avatar
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    Re: 657 vs. 657x engine comparison

    My SPX 657x blew up. I have a replacement 657 ready to go. Will it fit in as a straight swap?

  8. #18
    PWCToday Regular
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    Re: 657 vs. 657x engine comparison

    So I was trying to use this as a reference to figure out some cases and I learned some info. I have a 1994 Speedster n the cases have the tag that states the motors are 657x motors but when looking at the cases they aren't. In 1994 they used 657 cases and changed out the cylinders n heads. IDK about the crank shaft but I learned this by pulling the numbers off my cases n things. My motors are 657 cases with everything up being 657x. I've already mailed my cranks out to be rebuilt so I can't look to see if that's the same or if it had changed at that point. But if you are in doubt...find the casting numbers and look here.

    UPPER LOWER

    6810050 6810060 587

    6810058 6810062 657 pulse nipple right side.

    6810640 6810630 657 X pulse nipple left side.

    6810650 6810660 717

  9. #19
    PWCToday.com Is My Home Away From Home Mr. Bill's Avatar
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    Re: 657 vs. 657x engine comparison

    Can you say for a fact that someone has not swapped the cases or swapped the mag housings ?

    Does your stator have 4 wires or 5 wires ?
    Bill O'Neal
    www.watercraftmagic.net
    For repairs and/or parts and appointments only:
    626 914 9509 M-F 10 am to 5 pm PST, ask for Chris.

    Always speak your mind because those who mind don't matter and those who matter don't mind.

  10. #20
    PWCToday.com Is My Home Away From Home Mr. Bill's Avatar
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    Re: 657 vs. 657x engine comparison

    Quote Originally Posted by rupertmja View Post
    My SPX 657x blew up. I have a replacement 657 ready to go. Will it fit in as a straight swap?
    Yes if you use the stator and flywheel from the old engine.
    Bill O'Neal
    www.watercraftmagic.net
    For repairs and/or parts and appointments only:
    626 914 9509 M-F 10 am to 5 pm PST, ask for Chris.

    Always speak your mind because those who mind don't matter and those who matter don't mind.

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