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  1. #1

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    Realistic Expectations - a bit long

    Since the exposition of the 2007 Kawasaki Ultra 250 PWC, many of our customers have been asking us about our thoughts regarding this machine…. And the potential of all 4cycle PWCs as a whole. The attached document below attempts to address “some” of those customer questions.

    Happy Reading, Respectfully, Harry Klemm
    Attached Files Attached Files


  2. #2
    Very nice and informative article, thank you.

  3. #3
    Phil's Avatar
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    Great article harry. Thank you. Wow 3.38 hp/cid is incredible! I had a 250hp @ 8,450 rpms (on the dyno) 2003 Sea Doo GTX and put 140 hours on it without any significant problems. Now we have increased it to over 300hp @ 8,750 rpms with an EMS system. I hope I get as many hours. Most of my riding is at around 40mph with an infrequent burst to 72mph. I have been using Castrol GTX oil do to the SC clutch slippage problem with synthetics. Although the engine does burn quite a bit of oil (about 1 pint every 4 hours - probably because of blow by) it just keeps on running. I am buying a red 250. I told my wife I will keep it stock and just use the GTX for grudge racing, but we all know that I can't pass up a good speed mod. I think my stock GTX pump is the limiting factor on my top speed.
    What do you thinkg about the 250's pump? How much better is it than the Sea Doo pump?

  4. #4
    ....back from the dead.... J-ME's Avatar
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    Great read!

    Being and auto tech., I had to "reverse learn" when it came to working on my first 2 stroke PWC. I have to admit I love them and will probably never own a 4 stroke PWC.

    Not that long a ago Greg Anderson and his engine builders found that raising the red line and still keeping a productive power curve (of his 500 cid NHRA Pro Stock engine) they could get more engine power pulses in during a given run for a lower ET. Now everyone is building 10000 RPM engines in that class.

    Gotta love that (power pulse) ability of the old 2 stroke.

  5. #5
    way2fast's Avatar
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    The artical is informative but at the same time has more holes in it than a target at a pistol range. Regardless of what the "table" shows, in real life NO two stroke engine will have as much useful life as a 4 stroke. One of the primary reasons is lubrication. All the moving parts of a 4 stroke get superior lubrication compared to an engine where the only lube comes from oil mixed with fuel and burnt up in the combustion process. Stock for stock any 4 stroke PWC engine will out live a 2 stroke many times over. When heavy mods are added, both types of engines will have shorter times before maintenance is required.....that is a fact of life...but the 4 stroke will still have the longer life. The artical mentions 150-200 hours use on a PWC 2 stroke (in 10 years). How can anyone consider that a "long life" ? At an average speed of 45mph that is only 9000 miles. Even at 60mph it only equals 12,000 miles. I know of 4 strokes that have racked up well over 1000 hours.

    Richard

  6. #6

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    Richard,
    Please know that I didn't (and still don't) expect these words to be the last words on the subject.... just the starting point for the thoughtline.
    While I admire your un-dieing belief in the indestructability of high output 4cycle engines (being exposed to a PWC style operation cycle).... no part of physics supports your faith. The mere fact that PWC 4strokes have a power robbing valve train that requires lubrication puts 4cycles at a mathamatical disadvantage that needs to made up with super/turbo chargers. There is already volumes of data indicating that 2cycles have the mathamatical and physics advantage .... that is not (and never will) be in question. What is in question is the longevity of PWC 4cycles that are pressed beyond 3hp/CID while being used in normal PWC operational cycles.... and, for now, that is not known by anyone (short of IRL engine shops). That said, there is certainly enough good mathimatical examples to make some general predictions ..... and none of those examples infer that the longevity of a 3hp/cid 4stroke will have anywhewre near the longevity of a garden variety 2cycle platform. There is no doubt that a 3hp/cid 4stroke will be very very fast ... the only question is under what kind of maintainence interval ... none of us know that yet.

    Another huge variable that I chose to ommit from my article is that PWC engine longity is dramaticly challanged by the frequent intake of air laden with high humidity or even water itself .... something no other high output 4cycle platform has to contend with .... and two cycles have had a very "decent" reliability factor despite this exposure ....

    BTW... I've seen plenty of high hours 4strokes too ... but none were supercharged PWCs .... and I can absoluetly assure you that none where the new generation of 4stroke MX engines either.... on this subject it's very easy to make apples to oranges comparisons.
    Respectfully, Harry Klemm


    Quote Originally Posted by way2fast View Post
    The artical is informative but at the same time has more holes in it than a target at a pistol range. Regardless of what the "table" shows, in real life NO two stroke engine will have as much useful life as a 4 stroke. One of the primary reasons is lubrication. All the moving parts of a 4 stroke get superior lubrication compared to an engine where the only lube comes from oil mixed with fuel and burnt up in the combustion process. Stock for stock any 4 stroke PWC engine will out live a 2 stroke many times over. When heavy mods are added, both types of engines will have shorter times before maintenance is required.....that is a fact of life...but the 4 stroke will still have the longer life. The artical mentions 150-200 hours use on a PWC 2 stroke (in 10 years). How can anyone consider that a "long life" ? At an average speed of 45mph that is only 9000 miles. Even at 60mph it only equals 12,000 miles. I know of 4 strokes that have racked up well over 1000 hours.

    Richard

  7. #7

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    Phil,
    You bring up an excellent point. High output platforms are only at great risk when they are being asked to generate their full output (or close to it) for a big percentage of operating time. You certainly bought your GTX lots of extra engine life by reducing that amount of high output time.... no doubt a modified Ultra 250 would get the same benifit from your riding style. Sadly, very few owners of high output PWCs are as judicious as you are. Among engine builders it's called the "Toyota mentality" .... many owners think that simply because it's a 4stroke, it will always have Corrolla reliability... no matter how modified it is.

    The Ultra Pump is very likely going to be the new standard... by what margin... no one can say yet.
    Respectfully, Harry Klemm


    Quote Originally Posted by Phil View Post
    Great article harry. Thank you. Wow 3.38 hp/cid is incredible! I had a 250hp @ 8,450 rpms (on the dyno) 2003 Sea Doo GTX and put 140 hours on it without any significant problems. Now we have increased it to over 300hp @ 8,750 rpms with an EMS system. I hope I get as many hours. Most of my riding is at around 40mph with an infrequent burst to 72mph. I have been using Castrol GTX oil do to the SC clutch slippage problem with synthetics. Although the engine does burn quite a bit of oil (about 1 pint every 4 hours - probably because of blow by) it just keeps on running. I am buying a red 250. I told my wife I will keep it stock and just use the GTX for grudge racing, but we all know that I can't pass up a good speed mod. I think my stock GTX pump is the limiting factor on my top speed.
    What do you thinkg about the 250's pump? How much better is it than the Sea Doo pump?

  8. #8
    Moderator OsideBill's Avatar
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    Great to hear from you Harry. Welcome back

  9. #9
    EZ Dock of Long Island Shibby1485's Avatar
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    i think a rotary engine might be more reliable in a high performance PWC than these 4-stroke forced induction motors


    great article... these machines in stock form will run a long time... but with the power we WANT and we continue to squeeze out of them there's no denying the sacrifice in reliability we're making REGARDLESS of brand

  10. #10
    SpeedJunky's Avatar
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    Thanks for the article Harry. I found it to be informative.

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