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  1. #11
    I dream skis Wheelz22's Avatar
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    Re: Possible air leak in primer or primer plumbing ?

    Quote Originally Posted by johnlam940 View Post
    If the carb checks out, you might want to look at leaking crank seals. Original seals on an 1989"?
    They may be original.....I know I have personally never rebuilt the engine. But if the crank seals were suspect wouldn't that be more problematic when the engine was cold ?
    Northern fleet:
    85 550 (Power by PoM)
    86 550
    Southern fleet:
    89 550 (half owner, nice loaner ski)
    89 650
    92 550
    82 550 & 91 650 (don't own either, but do all the wrenching)

    (prop, plate, grate, bars on everything...and other assorted mods on the whole shootin' match)



    Member: SCCA, ALMS, IMSA Tudor Sports Car Series

  2. #12
    PWCToday Regular johnlam940's Avatar
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    Re: Possible air leak in primer or primer plumbing ?

    I had a blown out rear crank seal on my WB2 that gave me intermittent symptoms. It had me chasing my tail for a while.

    You should be able to get a good look at the rear seal by taking off the coupler shield and having a look with a mirror. For the front, pull the cover and check for oil/water sludge

  3. #13
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Possible air leak in primer or primer plumbing ?

    Meant genuine "Keihin"... And if memory serves Kawi didn't switch over to a 36mm Keihin until 1991 so your 28mm Keihin is the stock carburetor for 1988. You could try putting the stock PO spring back in, but if the boat ran good a few times after the rebuild that is probably not the problem.
    Anything that would cause the fuel/air mixture to be lean could cause a low rpm hesitation, so yes a leaking crankcase drain could be the problem. Or as someone else suggested, a leaking main seal could be it also. Or any number of other issues... Since your main seals may be 30 years old?
    Best to replace them and pressure test.

    Service manual doesn't say what weight spring or what pop off pressure, only that:
    main jet = 125
    pilot jet = 48
    low needle = 1 turn (below 1000' altitude)
    high needle = 5/8 turn (below 1000')

    Quote Originally Posted by Wheelz22 View Post
    Hey thanks for chiming in MCN.....I usually always use genuine Mikuni or in this case Keihin rebuild kits because it's the Keihin 28mm carb on the 89 650.....but this time I didn't. I replaced the needle with the one that came in the kit and it is the Viton tipped needle (rubber tip). I also used the spring that came with the kit. The kit did not come with a seat and I would not know how to remove it anyway...it look like it's pressed in...unlike a Mikuni BN38 whick screws in. From years of owning 550's with the BN38 round body, I know by memory that that carb takes a size 1.5 needle/seat and a 65-gram spring. I can't find any info on what weight spring the Keihin 28mm takes. The carb is stock and so is the engine. Do you happen to know ? However I did save the old needle and spring that was genuine Keihin. What's weird though was that the first few times I ran it after installing the rebuilt carb....all was normal. It's a head-scratcher. Shot in the dark on one more possibility....if the crankcase water drain became un-seasted or cracked and air was getting in when warm, would that cause my symptoms ?



    Home of Newmiller Machine

  4. #14
    I dream skis Wheelz22's Avatar
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    Re: Possible air leak in primer or primer plumbing ?

    Quote Originally Posted by mcn6 View Post
    Meant genuine "Keihin"... And if memory serves Kawi didn't switch over to a 36mm Keihin until 1991 so your 28mm Keihin is the stock carburetor for 1988. You could try putting the stock PO spring back in, but if the boat ran good a few times after the rebuild that is probably not the problem.
    Anything that would cause the fuel/air mixture to be lean could cause a low rpm hesitation, so yes a leaking crankcase drain could be the problem. Or as someone else suggested, a leaking main seal could be it also. Or any number of other issues... Since your main seals may be 30 years old?
    Best to replace them and pressure test.

    Service manual doesn't say what weight spring or what pop off pressure, only that:
    main jet = 125
    pilot jet = 48
    low needle = 1 turn (below 1000' altitude)
    high needle = 5/8 turn (below 1000')
    Thanks MCN....and thanks johnlam940....yeah, I'm gonna put it in the water tomorrow for some real testing with a load on it. When I reinstalled the carb last week, I put some dry-gas in it and filled the tank with new pre-mix....so the dry-gas has had several days to work (if there was water in the tank) . The oil pump was deleted long ago, so I use pre-mix.

    Yeah, the 28mm Keihin that featured the remote fuel pump was found on 87-90 650SX. In 1991 Kaw went to the Keihin 38mm carb....my buddy has a great running stock 91 650 with that carb. I was looking through some old notes of mine from when I first rebuilt the carb in 2008....that note had all the info you just gave me and also that the spring is 70 grams...but I don't know where I got that info from at the time. But 70 grams would make sense for a stock 28mm carb on a stock engine. Either way, I found a guy selling some NOS (new old stock) parts on the internet and he has the OE spring with original Kawi packaging. So I got that in case the one that came with the knock-off kit I bought is not correct.
    Northern fleet:
    85 550 (Power by PoM)
    86 550
    Southern fleet:
    89 550 (half owner, nice loaner ski)
    89 650
    92 550
    82 550 & 91 650 (don't own either, but do all the wrenching)

    (prop, plate, grate, bars on everything...and other assorted mods on the whole shootin' match)



    Member: SCCA, ALMS, IMSA Tudor Sports Car Series

  5. #15
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Possible air leak in primer or primer plumbing ?

    1991 and newer CDK38 has a 36mm venturi so it is actually a 36mm carburetor. Your carb (CDK34) has a 28mm venturi.

    If it were me and if the re-build kit you used is AM I would put the original spring back in there and see what happens.



    Home of Newmiller Machine

  6. #16
    I dream skis Wheelz22's Avatar
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    Re: Possible air leak in primer or primer plumbing ?

    Quote Originally Posted by mcn6 View Post
    1991 and newer CDK38 has a 36mm venturi so it is actually a 36mm carburetor. Your carb (CDK34) has a 28mm venturi.

    If it were me and if the re-build kit you used is AM I would put the original spring back in there and see what happens.
    Yeah, I heard that info about where carbs are measured years ago. on the body of my carb in the casting it just says CDK, not CDK34....just some info.

    Anyway....can't thank you enough for your advice. Problem resolved and rode that baby for three hours today without a hitch. Got to the beach early...and brought the old spring with me. Started it up in his back yard....held a perfect idle.....but it was dying out when throttle was advanced past idle. So pulled the carb real quick, re-installed the old genuine Keihin spring from 10 years ago and boom.....purring like a kitten and snappy throttle response and quick starts all day long on the water. Funny....I'm a genuine parts guy when it comes to rebuild kits.....but I strayed this time to save a few bucks....foolish move. I asked my buddy for a second opinion....he checked both springs between his thumb and fore-finger and said that the spring that came in the aftermarket kit was stronger than genuine Keihin. I thought that too when I did the same test last week...but I foolishly installed it anyway. The one in the aftermarket kid had a few more coils and looked goldish rather than silver. So I guess it was pop-off pressure that was causing the dieing-out problem ? If you had to guess what do you thing the stock pop-off psi is on that carb ? Just curious. Also.....the carb no longer drips fuel into the throat when engine is off.....but it wasn't dripping with the wrong spring this morning. What do you figure was causing that ? Thank you my brother for your guidance.
    Northern fleet:
    85 550 (Power by PoM)
    86 550
    Southern fleet:
    89 550 (half owner, nice loaner ski)
    89 650
    92 550
    82 550 & 91 650 (don't own either, but do all the wrenching)

    (prop, plate, grate, bars on everything...and other assorted mods on the whole shootin' match)



    Member: SCCA, ALMS, IMSA Tudor Sports Car Series

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