Advice On Testing Regulator/Rectifier

Discussion in '2 smokers' started by Edmond Dantès, Jan 29, 2015.

  1. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    Hi everyone,
    My 1993 KDX250SR was not starting and kept backfiring so I:
    cleaned the carburetor, cleaned the air filter, installed a new top end; new piston / rings/ small end bearing / KIPS valves, new reed valves, repacked muffler, new spark plug.
    The bike starts and revs fine, but bogs down/loses power when I try to ride it.
    I had a similar problem many years back and a mechanic fixed it with a new reg/rec unit.

    I am trying to test the regulator/rectifier at the moment.
    My workshop manual doesn't have any information on how to test this unit, and youtube videos deal with units with one or two plugs.
    My unit has plugs:
    3 yellow wires in a plug
    1 red wire in a plug
    1 brown wire and 1 black and yellow wire in a plug

    Could anyone give me a heads up on how to go about testing the reg/rec with a digital multimeter?

    Any advice would be very much appreciated.
    Thank you in advance.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
    #1
  2. dtysdalx2

    dtysdalx2 Just glad to be here.

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    It's easier to test on the bike, running actually.

    All you can do off the bike is test the bridge rectifier and diodes.

    The 3 yellow wires are for the stator input. Not sure if it's a 3 phase stator though. Sounds overkill for a KDX.

    Hard to see the R/R as the problem for bogging too.
    #2
  3. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    D.T.,
    I have the bike running, albeit it's still a little boggy down low.
    I got to thinking that the new Boyesen reeds may have upset the jetting and so I moved the needle up a notch and fiddled with the pilot screw. It's revving crisp through the throttle, but feels a little sluggish down low and the revs hang a little when ticking over, that is, it takes a little while for the bike to tick over after slowing down.
    I pulled the exhaust valve shaft to make sure that it was operating, and it's doing its job.
    I am taking it easy for the first tank of gas, so I can't open up the bike fully as of yet.

    Anyways, I'll take this current situation over trying to troubleshoot an electrical fault any ole day of the week.

    Any advice on the revs hanging high on tick over (it does it intermittently) would be very welcome.
    #3
  4. third eye

    third eye back road loon Supporter

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    I'm doubting that's a fuel screw you are adjusting. If it's on the air box side of the carb, it's an airscrew and you might have it opened up too much. Try setting it at one turn out from lightly seated after you check your float level height. Your idle hanging up is a lean condition
    #4
  5. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    Thanks Third Eye.
    I'll check the float level and adjust the airscrew.
    #5
  6. third eye

    third eye back road loon Supporter

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    curious to see what happens
    #6
  7. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    Well, I had the float level checked and okayed.
    I spend a whole day trying to dial in the carb.
    I had the damn thing on and off more times than a cheap hoe's draws. It either bogged down low or stuttered on the pick up.
    I threw every bastard jet and needle combination in my repertoire at it, but to no avail.

    Out of desperation, I screwed on a carb which I had lying around from a KDX220.
    The bike is now picking up smooth throughout the throttle openings with a decent hit when the power valves open. Too early to ascertain if the power is down from the 250 carb, as I am still (trying) to run in the top end.

    The 220 carburetor is currently set at:
    Pilot:38
    Main:158
    Needle: 2nd from top
    Slide: #5 with 1 mm cut off

    Something must be amiss in the old carb.
    Terrible really! I had only 60,000 k/m on it without ever overhauling it!:lol3:lol3:lol3
    I'll get a repair kit for it, replace everything inside and see about having another bash.

    I need to have this little bike running well. It effects my standing in the universe; when the bike is running well I feel at one with everything, in equilibrium. When it is out of sorts, I feel pissed off!

    My wife keeps telling me to throw the damn thing in the river already. I retort with I was riding the bike when she was still playing with Barbie dolls, so put a sock in it sweetheart!
    #7
  8. PistonPants

    PistonPants Crankcase Scavenger

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    If you were riding this bike while the spouse was playing with Barbie, then obscure parts in the carb could be bad. 'Cleaning' carburetors with carb cleaner spray or soaking in solvent is also harmful, and this bit of rubber is prone to decay in old carbs. The jet block is held on with little tamper resistant screws. On the usual KDX Keihin PWK its an oval shaped seal with attached smaller o-rings on the sides. These things wear out and cause rich symptoms that are impossible to jet out. Old carb? Replace this $4.50 part.

    Piston
    #8
  9. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    Aye, I see those two tamper-proof puppies Mr. Keihin put in there. Am I to remove them, and where on God's green earth can I find the replacement seals?
    #9
  10. PistonPants

    PistonPants Crankcase Scavenger

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    #10
  11. third eye

    third eye back road loon Supporter

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    ^^^^^^^ glad somebody knows what their doing^^^^^^^^^
    #11
  12. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    Mr. Piston,
    thanks for the heads up bro.
    #12
  13. dtysdalx2

    dtysdalx2 Just glad to be here.

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    :bow

    This is what these forums are all about. I was about to give up hope.
    #13
  14. PistonPants

    PistonPants Crankcase Scavenger

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    No guarantees on that, but a $4.50 part can rule out that problem. I learned of this bit over on KTMTalk (the best technical forum). Let me know how it works.

    Piston
    #14
  15. PistonPants

    PistonPants Crankcase Scavenger

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    OK, in case you haven't made it this deep yet, I'll show you what I found. This is the PWK carb. The consensus that I've researched says don't monkey with jets 'til the jet block o-ring is known to be good.

    Here it is, the jet block held on by tamper resistant screws:
    [​IMG]

    I had to borrow Tardy Mike's security bit set to undo the screws. Get a bit. Don't kludge it. The screws have blue loctite on them. Vibe-proof.
    [​IMG]

    Off with the jet block. You'll find something like this. Easy to imagine leakage on this gnarly old seal.
    [​IMG]

    [​IMG]

    The old o-ring scraped out in flattened dry-rotted pieces, along side the new o-ring:
    [​IMG]

    Now the jet block and the carb body can be cleaned out good with lacquer thinner, toothbrush, compressed air without messing up this internal o-ring. Carefully re-assemble and your carb should no longer be getting crossed signals form leakage. Hope this helps!

    Peace

    Piston
    #15
  16. third eye

    third eye back road loon Supporter

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    I took one of those apart couple years ago while trouble shooting a KDX250. O-ring was OK, ended up being a worn out choke plunger being the culprit
    :puke1
    #16
  17. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    Awesome post Piston.
    #17
  18. Edmond Dantès

    Edmond Dantès The Kanto Pain

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    I thought this could be the culprit, too.
    I took the choke plunger off and it seemed fine.

    Piston's advice about not further trying to setup the carburetor without taking off and replacing the o-ring sounds solid.

    -apparently the 91' KDX250 has a different carburetor than the 92-94 versions.
    -the overseas export bikes are different from the domestic Japan bikes.
    -the general word around the campfire to get the jetting in the ballpark is:

    38/158 , R1367H needle 3rd clip from top, #6 slide
    (This is with U.S. bikes)

    I couldn't find the R1367H needle nor a #6 slide (the slide I received from JD Jetting was too big)
    I finally found a company here in Japan that makes a jet kit for the bike with a needle close to the R1367H.
    I had 1 mm machined off the slide to approximate the #6.

    I followed jetting lore to the T, with tuning the pilot and air screw, then the needle, and then the main with the plug chop.
    I got the bike to run real good in the spring and summer months, and slightly off, but livable for the cold, dry months of Jan, Feb.

    Prior to the recent top end rebuild the bike started bogging down, so I thought it a opportune time to redo the top end. So with a new top end, cleaned air filter, new Boyesen reeds, new carburetor manifold I am still in the 'bog house'.

    Out of interest, what carburetors do the '91 and then the '92-'94 250s have in the US?

    My bike is a 1993 F3 (D3) SR version.
    Stock Settings:
    Keihin 35mm
    148 main
    42 pilot
    #5 slide
    #18
  19. PistonPants

    PistonPants Crankcase Scavenger

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    Anything to help your KDX and your standing in the Universe.

    Piston
    #19
  20. third eye

    third eye back road loon Supporter

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    I verified the choke plunger being bad by spraying brake cleaner into the choke port and watching it ooze/drain past the plunger.
    Just an fyi
    Two strokes can be tricky to work the bugs out sometimes.
    Where in Japan are you? I was in Yokosuka in the Navy years ago. Totally miss riding there.
    Crashed my FZ600 on Mt. Fuji :lol3
    #20