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2 out of 4 aint bad.

Discussion in 'XJ Technical Chat' started by Greenbroke, May 17, 2021.

  1. Greenbroke

    Greenbroke New Member

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    Here I am with an 82 SJ650J Maxim. I know it's a 4 cyl machine but it insists on being a 325 2 cyl. I'm an old man who has pulled wrenches all my life...built street rods, rode a few 2 wheelers, worked on cars, bikes, cranes, dozers and everything in between. This Yamaha has me scratching my head. Bought it from the original owner in Jan this year with 4500 real miles. Last PA inspection is 93. Took some time and parts to get it cleaned up and running. Starts if you touch the button. A cold natured rig for sure it needs the fuel enrichment cycle. BUT it runs on #3 and #4. Therin lies the puzzle. Has spark. Has compression. Has fuel. Wore the carbs out R & R 'ing them. Have a spare set and no different. Replaced-- Plugs. Coils. Ign. unit. I'm in dire need of a genius. Anyone want to take a stab at it????
     
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  2. StahlMaster

    StahlMaster Active Member

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    Spark plug wires and plug caps?
     
  3. Jetfixer

    Jetfixer Well-Known Member

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    Check the grounds at the coils , the other item is the plug caps , you could have corrosion, unthread cap, snip off a 1/4" of plug wire and thread back in . The carbs a problem with the " choke" this is actually the fuel enrichment circuit, to clean you have to pull the carbs , pull the float bowls . At the forward edge there is a well at the bottom is the enrichment jet....to clean it out 0.20 thousands wire , and take a can of carb cleaner with the spray nozzle CAUTION point it away from you spray both directions on it. If it is clean will squirt about about five feet . While float bowls are removed spray the pilot and main jet is not a bad idea either.
     
  4. Greenbroke

    Greenbroke New Member

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    Plug wires are part of the coils and are new as are the plugs. Coil grounds are clean and tight. (FYI the original coils tested OK) Carbs were stripped, soaked, blown, "choke" circuit in the fuel bowls were cleaned and passing fuel. {It starts at the touch of the button and runs fine. Once warmed up ("choke" off) it responds to the throttle well, on both #3 & #4. Actually runs ok.} Carb primarys are at recommended 2 1/2 out, synced, the YICS blocking rod is in place. What else ? All the jets and ports are clean and passing (cleaner/)fuel. Floats are at specs. all the diaphragms are OK. Compression is at spec. I am of the opinion the carbs are at fault but after removing, stripping cleaning, assembling, checking and reinstalling, I pulled the spare set out and went thru the procedure and tried them (again and again and again...). Same result.
     
  5. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Interesting problem. I wish I had brilliant insight.

    My only advice is: DONT GIVE UP
     
  6. Greenbroke

    Greenbroke New Member

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    Thanks for the replies. I also have a 74 TX650A waiting to be repaired. It has about the same mileage, under 5,000. And an S40 Suzuki and my wife and I have a pair of Kawasaki Vulcans in case we want to take a trip!
     
  7. Minimutly

    Minimutly Well-Known Member

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    Are you sure you're getting spark with the middle two? Have you put a plug in one of the tops and held it on the head with the engine running? If not do it.
    If you have a confirmed spark, pull the coil feed, does it run differently?
    The odd thing is, if the middle two are dead all the time its not your idle mixture, IOW when you open the throttle you're up onto the idle jet, even the main jet if you blip it. And the middle two are still missing? Exhausts cold?
    Then you need to open the carb drain screws to check there's fuel in there - did you wet set them?
    Good luck
     
  8. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Vacuum leak on 1 and 2?

    And the plug caps were checked / replaced?
     
  9. Greenbroke

    Greenbroke New Member

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    Minimutly, this rig is running on 3 & 4 which are the two right hand cylinders under my throttle. Hot exhaust via Infrared unit. 1 & 2 are getting spark via spark tester and these exhaust are room temperature. Have not wet set the carbs. The plug caps are new with the coils and a tight fit. Fuel is present in all carbs every time I pull them or switch them out. #1 & 2 were in the beginning running OK. Last time I pulled the plugs #2 was wet. Haven't touched it for a couple days. The wheels are finished ready with new rubber. Just couldn't ride on 40 year old tires. Will pick them up tomorrow. I'll keep you informed. Okinawa Joes here in Harrisonburg (VA) specializes in vintage Japanese bike but he is a restorer and dealer,,,,not a repair shop. But full of great advice. And some beautiful bikes. He is my next stop!
     
  10. 50gary

    50gary Active Member

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    Cylinders 1 & 4 are run off the left side coil. Cylinders 2 & 3 are run off the right side coil. Check the wiring just to make double, extra, plus sure they are correct.
    Cheers, 50gary
     
  11. Minimutly

    Minimutly Well-Known Member

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    Ah poo, you see, I should really learn to read..
    So you have spark from both pickups, the coils are double ended, and unless leaking down on one side you must have spark both sides.
    Get some new plugs, check the fuel level (wet set). I once had a mate who had a suzuki pickup, two cylinder thing, delivering milk. It ran like poo, even after a rebuild. Running out of ideas we removed the exhaust manifold - it was clogged hard with carbon. You haven't got a critter in there have you?
    Tell you what, remove the whole exhaust - you might learn a lot?
     
  12. Jetfixer

    Jetfixer Well-Known Member

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    Okay just went through my Johnny Cash bike seaming to running on three cylinders, on mine had one cylinder with no gap on intake valves . And another the exhaust was almost out . So have you checked valve clearance?
     
  13. Franz

    Franz Well-Known Member

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    I was going to say valve clearances but didn't because of the 4500 miles if that is all the bike had done from new. Then again it is easy to check them.
     
  14. tabaka45

    tabaka45 Well-Known Member

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    If you go into the carbs again strip them down and put then in boiling water for 10-15 minutes and then blow them out with carb cleaner. The boiling water melts the varnish that might be in the very small passages. It sure helped mine by doing that.
    Also, as mentioned earlier, check for a vacuum leak. When I got my bike the #1 cylinder would only fire with the pilot screw open about 5 turns. It turned out that the intake gasket was torn and pulling a lot of air. Replaced the gasket and all was well. While you have it at idle open the pilot screw and see if that gets the cylinder firing.
     
  15. Greenbroke

    Greenbroke New Member

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    Visited Yokohama Joe's and got a little education on NGK plugs. Seems they don't like to get wet flooded and often never really recover. Did a cold compression check again on #1 & #2. Following good advice I also rechecked spark and the tester was bright while the plugs were NOT. Reinstalled original (NGK) 2 plugs in 1 & 2 and fired it up again. Surprise! Runs great on all 4. I replaced the glass tube fuses with a plug in unit and eliminated another occasional problem. Now if the YICS block off tube would just come out. Maybe after a night of rest and cool down it will extract easier.
    Really appreciate all the advice. Time to ride this ZJ650J and start on the 74 TX650A!!
     
  16. Jetfixer

    Jetfixer Well-Known Member

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    Autolite AP63 or 63 work great and are cheap as well ,these are direct cross reference to NGK . The YICS tool makes a nice door stop , I don't use it.
     
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  17. Greenbroke

    Greenbroke New Member

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    How do you sync the carbs when they are all interconnected thru the intake ports??
     
  18. StarGeneral

    StarGeneral Active Member

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    Yics tool
     
  19. Greenbroke

    Greenbroke New Member

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    Update.....My original May 17 post until the plug change was a puzzle! Afterwards I rode with an intermittent miss for a day or two and finally replaced all four of the NGK plugs with a brand I never heard of -E3, Recommended by the young man at our local Advanced. Immediate results! After a few hundred mile the bike starts instantly, Runs very well and will clock 10,000 RPM in a heart beat. It is a pleasure to ride! This Shenandoah Valley is a great place to ride with an abundance of roads worthy of exploration. Enjoy the years the Lord has granted you!
     
  20. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Or not. Mine is still sealed in the plastic that it came in 15yrs ago.
     

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