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Bike almost blew up! HELP!!!

Discussion in 'XJ Technical Chat' started by vintagerice, Feb 22, 2010.

  1. vintagerice

    vintagerice Member

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    Ok... Putting the finishing touches on the bike today, siked to get the side covers and tank put back on etc. I get the idea to start her up since I had the carbs off earlier in the season to replace the carb joints.

    First attempts nothing.. just turns and turns til the battery grows weak. I get a low amp booster and keep trying. Turns over nice and quick but no fire.

    I take out a spark plug from each side of the motor and shoot a couple squirts of carb cleaner in the hole.

    Then Eureka! Fires right up but running about 4 k rpm and steadily increases, motor is getting hot starts smoking a bit. ( likely from the fresh paint this winter)
    It keeps gaining rpms up to about 7 k and then I cut the machine off.

    Goosing the throttle only made it climb more.

    I start it up again and starts right away and back to the high racing. Trying to figure what is going on.. it climbs again and I shut it off. This time it backfires BANG!

    I thought I better keep it off and see what the hay might be going on. Any thoughts? As I mentioned carbs were taken out but no adjustments made. They were running great before the winterization.

    I did replace the carb joints, I also replaced valve cover gasket,put on an inline fuel filter and replaced the tank on the machine. I put the valve on Pri to get the fuel to flow to the filter. Did not appear to be any obstructions.

    What could it be???

    Thanks
    Rob
     
  2. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    The most common cause: You trapped the throttle quadrant under the fins on the back of the head when you put the rack back on, and the throttles cannot close completely.

    Second most common: You mixed up the throttle and choke cable ends upon reassembly.

    I vote #1, and the hard start was because the throttles were being held open.
     
  3. rpgoerlich

    rpgoerlich Member

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    Or possibly caught the throttle on #2 or 3 carb boot clamp if it's turned up some.
     
  4. Lou627

    Lou627 Member

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    It might be from the residual card cleaner in the cylinder. Leave your spark plugs out and let that evaporate out. I would think that isn't the best method of starting your bike up... A little starting fluid sprayed in the airbox would be the way to go.

    Did you adjust your idle screw? Is the throttle hung up? Mabey you have an air leak. Did you cap you synch ports on the carb to engine boots? is your vacuum line to tank airtight?

    If all looks well, start it up again. If your not racing to the point of overheating, spray some of that starting fluid you picked up around your carb to engine area and see if your rpms increase. This will indicate and air leak somewhere. Let us know
     
  5. Chrish

    Chrish New Member

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    If you need to use starting fluid try WD40 instead. Ether washes away any oil on engine parts and WD40 adds it but is combustible to start your engine.
    Run your idle screw way down and look for a vacuum leak.
     
  6. mcrwt644

    mcrwt644 Member

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    I've had the exact same thing happen. It was one of four things

    1. throttle and choke cables mixed up

    2. throttle cable is binding

    3. Throttle cable is mis routed

    4. The idle is set WAY too high. Stick your hand in there when it is running up there and turn her to lower the idle. I'd check the other things first as they don't involve burning the heck out of the back of your hand. Try unwinding the idle screw a bit before start up, start it up, see if there is progress and go from there
     
  7. RickCoMatic

    RickCoMatic Well-Known Member

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    If you didn't "Tie-off" the Throttle Cable Connection to the Carb Linkage before you reinstalled the Rack ... the Cable Attachment slide up under the Head and holds the Throttles nearly wide open.

    Trying to save time and reinstalling the Intake Maniold Clamps upside-down or off centered will cause the Clamp to come into contact with the linkage.

    Installing the Manifold Clamp in the wrong position will also cause the Clamp to cut into the Manifold causing a severe Air Leak.

    Age. Deteriorates the Intake Manifold O-ring allowing Air to be drawn into the Intake.
     
  8. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    Yeah, good advise, but he said it sat at four grand, which is just off idle or so. It wouldn't be the misaligned throttle syndrome, or a massive air leak in 1 carb.
     
  9. vintagerice

    vintagerice Member

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    I will take another look at it tomorrow. I was wondering if the old carb joints had some leaks due to cracking the PO may have leaned out the screw to compensate. Now that the boots are new perhaps it is getting to much draw?

    I don't know.. Other than that I will check to see if anything is getting hung up. I looked prior to starting and the throttle moved nice and free and I was able to see the linkage open and close quite nicely.

    Thanks for some pointers.

    I don't think it has any bearing but I also changed my grips on the bike.

    Rob
     
  10. KrS14

    KrS14 Active Member

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    Sounding like a vac leak to me, interested to see what this resolves to :)
     
  11. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    Just reviewed this, and no one said to leave a little slack in the throttle cable- - an obvious blunder.
    Does it idle down if you press the linkage closed?? Adjust idle screw??

    A single sync screw way out of adjustment can do it also.
     
  12. vintagerice

    vintagerice Member

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    Went out and tried again. Same thing. No start. then shot some starting fluid in the airbox. After several attemps it fired right up and was reving up around 7k rpm and climbing. I shut it off and tried again. Started up immediately and at a high rpm. Thing would have redlined if I didn't shut it off.

    Then from the left side of the bike I reached in and tried to adjust the center idle screw. Started and still reved like crazy, turned the screw all the way tight(to the right) and no difference. still was a rocket ship ready for take off.

    I copied everyones suggestions and went out and examined.

    *Appears to be no binding of the linkage, it moves freely with the twist of the throttle and snaps back to position with ease.

    *Choke and throttle are in the right places, I know this because I replaced the choke when I got the bike it was snapped.

    *As best as I can see the carb boot clamps are not interfearing with the movement of the cable

    *Not sure if there is an air of vac leak? Not sure how to figure that out but seems to me that the bike would run rough with a vac leak. Other than the fact the bike is near the redline it runs strong and smooth as if you were blazing along the highway at a 100mph.

    What else can I do?

    Very discouraging.

    Thanks,
    Rob

    Oh and now that I filled the gas tank I am affraid to take it off. Is there a way to shut off the fuel so that the gas doesnt piss all over my freshly painted engine?

    I have pri, on and res no off.. I know this have been discussed to adnausem but my brain is frozen.
     
  13. vintagerice

    vintagerice Member

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    Time2

    I never adjusted any sync screws. And how does one leave some slack in the throttle cable? I do recall forgetting to put the cable on the rack prior to installation and I fought to get it on. really had to stretch and pull the cable and just barely made it. I was affraid I would snap but it didn't

    Rob
     
  14. vintagerice

    vintagerice Member

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    Bigfitz,

    What is the throttle quadrant? And where is it located. Can't find it in the Haynes.


    Rob
     
  15. Krashen

    Krashen Member

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    On my 550 I think the petcock works the same way on your 650. But when you have the petcock on res or on it does not let gas out of the tank without vacuum.
    also have you tryed sdjusting the cable up by the bars there should be some nuts up there you can use for adjsutment.
    Krashen
     
  16. vintagerice

    vintagerice Member

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    Good point, I'll go take a look.

    Thanks
     
  17. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    You may need to pull your tank to more efficiently route your throttle cable, then you'll be able to figure out how to leave about 2MM of loose slack. There's an adjuster at the grip also.

    I'm bettin' $5 bux that's the problem !

    (I think the "quadrant" is the term for the hinged part of the throttle linkage where the cable connects)
     
  18. iwingameover

    iwingameover Active Member

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    Try turning it loose (left). That'll let the throttle blades close.

    Did you bench synch the carbs? Maybe a butterfly is hanging up inside a carb.
     
  19. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    You seem to be describing RAISING the idle- - go counter-clockwise

    You should leave it on "ON" and pull the fuel line. It should not drip (much)
    If it pours out, you make up a plug using an inch of fuel line and a bolt. Throw a plastic bag and a towel over your engine.
     
  20. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    I think TIME has hit the nail on the head; if you were "tightening" the screw you were turning the idle UP.

    You should be able to introduce some slack into the cable with the adjusters at the handlebar end;

    And yes, I was referring to the thing the cable attaches to/wraps around, at the rack.
     
  21. vintagerice

    vintagerice Member

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    Good stuff guys.. thank you. i will give it another shot tomorrow. I am hoping rerooting the cable will do the trick (fingers crossed)

    Just really bummed, the bike looks great and hoping it will run just as good as it looks. I have dropped more cash into it then I paid and it truly is a labor of love.

    More later...

    Rob
     
  22. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    I hope you don't think you're alone in that... did you see what I named my '83?
     
  23. RickCoMatic

    RickCoMatic Well-Known Member

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    If we all got paid for the time we spent and spend working on our Bikes, at anything close to the prevailing fee for labor, ... we'd all be rich and entertaining guests on our boats.

    (I'd like to have back ... just the money I've spent on Tires, Batteries, Brakes and Clutches.)
     
  24. Robert

    Robert Active Member

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    I'll also mention that a few of us (come on, you know you've done it too) have hung the end of the throttle cable ferrule on the throttle cable stop locating shoulder, leading to high rpm at start-up.
     
  25. mcrwt644

    mcrwt644 Member

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    x100, you raised the throttle vs lowering it.

    labor of love is an understatement. I've got 3500 into my maxim x
     
  26. vintagerice

    vintagerice Member

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    Ok so what does this mean? two cables?? I only noticed one but could this be the reason my throttle is sticking wide open?

    Below is something I found on ebay while looking for a new cable

    Here is a THROTTLE 'PULL' cable that will fit Yamaha XJ650 models from 80 to 83.

    PULL vs PUSH - Which cable do you need? Just to clarify, if your bike uses a single cable, this PULL cable is the one you need. If your bike has two cables the one that does the work when you twist the throttle to rev the bike is the 'PULL' cable (sometimes called the 'A' cable). The 'PUSH' cable (sometimes called the 'B' cable) is the secondary cable that makes sure that the carb can't stick in the full throttle position. The pull cable usually wears faster than the push cable because it works harder.

    This cable is made by Motion Pro so you know that it's good quality and it's going to last. You can find cheaper cables on eBay but why take a chance on buying some imported junk just to save a buck?

    We have great deals on other important stuff that you need like filters, levers, bearings and seals. Check out our eBay store:
     
  27. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    You're reading E-Bay blabber that vendors put in every ad to cover their butts. You have a single "pull" cable.

    My Venture Royale has 5 (FIVE) throttle cables !! Jeez !

    Buy from Chacal- - he'll get you the right part.
     
  28. vintagerice

    vintagerice Member

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    That is true. I was just oput there looking for info and came across the site on the bay.

    Thanks..

    Rob
     
  29. vintagerice

    vintagerice Member

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    Well, went out there today to try and get things right.

    Started the bike after loosening the adjustment on the throttle cable. Still revving high. I shut it down, dialed the carb adjustment way to the left and tried again. Still high but better. I then reached in the throttle mount on the carb rack and was able to push it down further than the throttle was apparently bringing it with a twist.

    This brought the idle down to an acceptable level. YEAH! except obviously there is something making the cable not retract enough. Problem found but still no explaination?

    I then noticed the cable was noisy at the grip and sounded gritty like there were sand in the throttle grip. I sprayed some silacone in it and began to twist onle to have the throttle break free. Free enough that I realized the cable snapped.

    So needless to say I have contacted Len for a new cable but in the meantime could a frayed / stretched cable have been causing the high throttle and rpm's and not returning the throttle to the normal position on the carb rack?

    Or will I likely still be plagued with this problem when I install the new cable?

    By the way my valve cover was pissing oil fromn the new gasket I applied earlier this winter. Seems there was a spot where it was pinched so I loosened all the doughnuts fixed the pinch and reinstalled.

    I then managed to overtighten one of the bolts and snap my newly refurbished valve cover. Talk about a crappy day on the bike today. Can't wait till riding season so I keep my hands off the bike :roll:

    Rob
     
  30. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    Maybe some of it, but the carbs would want to return to a positive stop and would shove a stuck cable.
    Try running it with the throttle cable off, and the idle set screw all the way out. Then the only thing else holding your throttle open is a mal-adjusted butterfly.

    Really !! Damn your bad luck !!! Where's the JB Weld !!
     

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