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My 1980 XJ650 Project - Not Easy

Discussion in 'XJ Technical Chat' started by Palmer650#2, Mar 30, 2016.

  1. Palmer650#2

    Palmer650#2 Member

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    Hi Gurus,

    I am rebuilding the carburetor and ran into an issue that I need you to help shed some light on. I broke the rack and separated the carbs for shaft seal replacement. After removing the valves (look like silver coins) from the butterfly shaft I found that 3 of the 4 butterfly shafts would not come out. After using lots of WD-40 and a large punch and hammer I was able to knock them free of the car body. The shafts would no go back into the carb bodies without some sanding/polishing (1500-2000 wet or dry paper) of the shaft ends and carb body receiving holes. After the carbs were reassembled I found that the valves (silver coins) will not seat properly for bench synching. There is still light around the valves and I cant get them to seat tightly. The valve on carb #1 is rubbing badly against the inside throat of the carb body which is especially strange since there isn't any thing holding in the shaft but some shims and an E-clip. Please help!
     
  2. rocs82650

    rocs82650 Well-Known Member

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    I'm no guru but the shafts and throttle plates must be oriented and relocated the exact way they were removed.

    Gary H.
     
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  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    the shafts are sealed with throttle shaft seals. replace them.
    did you mark the butterflys as to the carbs they came from?
    they do not completly seal the carb throat you will see the light.
    disc #1 is probaly in the wrong hole



     
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  4. Palmer650#2

    Palmer650#2 Member

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    image.jpg
    Yes, I replaced the seals and made sure to put the correct valves back into the proper carb. I took apart the rack again and found that Carb #2, 3, & 4 are closing completely. #1 will not close completely no matter what valve/disc I install. Something is wrong and I cannot figure out what. Here is a pic above of what #1 looks like as opposed to the others below when light is on inside the carb body. image.jpg
     
  5. Palmer650#2

    Palmer650#2 Member

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    This is #1 carb fully closed. It's still open at the top and the little holes are visible. image.jpg image.jpg
    This is how carbs 2-4 look when in closed position. No holes visible.
     
  6. rocs82650

    rocs82650 Well-Known Member

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    Inspect the spring and linkage orientation. Loosen the screws and see if the plate will shift.

    Gary H.
     
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  7. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Loosen the throttle plate ("valves") screws so the plates can settle into place, then tighten them. Don't forget to use a medium strength thread locker.

    If they still don't close completely, mark them (use letters so you don't confuse them with the carb numbers) and move them around until they all fit. It's easy to mix them up if you did not mark them with the number carb they came off of (all I see is orientation arrows).

    Your pic for the #1 carb is how they should all look in regards to the idle byass hole (second hole) when they have been bench synched.
     
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  8. BigT

    BigT Active Member

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    It's been a couple of years since I replaced my throttle seals so my memory is a bit fuzzy, but I did have trouble with one of my throttle plates not closing properly. After much head scratching and reviewing pictures I had taken before disassembly, I believe I had the throttle shaft turned the wrong way. After turning the shaft and mounting the throttle plate to the other side everything lined up and it snapped shut properly.
    Hopefully I am remembering that correctly!
     
  9. Palmer650#2

    Palmer650#2 Member

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    The good news: I think I found and solved the issue. When I had to tap out the throttle shaft with a punch and hammer, I believe it slightly deformed the carb body so the valve wouldn't seat properly.

    Last night I loosened up the screws and actuated the throttle shaft multiple times to make sure the valve was seating properly. I tightened up the valve screws and actuated the throttle shaft a dozen times quickly to see where the valve was getting hung up. The valve left two pronounced dark marks where it was rubbing too close on both sides of the carb body, right near the shaft holes. I took out the shaft and valve again and lightly sanded with 1500 and WD-40 until the areas were smoothed out. I assembled, checked, marked high spots, disassembled and sanded multiple times until the valve closed all the way over both little holes in the top of the carb body (like 2,3,&4 do). Now the valve opens and closes smoothly and tightly not allowing tons of light through when I shined the flashlight thought the air intake side of the carb.

    The bad news: I destroyed one of the new throttle shaft seals with all the dissembling. It got pinched and a little piece tore off. But that's not too bad, i also have to order a new pilot o-ring too since it dropped out during the installation and I can't find it anywhere.

    I replaced float needles, and needle seats, pilot o-rings, throttle shaft seals and screws. I also rebuilt the caliper, new pads, got a new master cylinder, brake lines (Although I'm in the process of getting a test fit line made for flatter bars.) I got new manifolds, air boots, air filter, fuel line and 90 degree filter, plus color tune and 4 column synch gauge. Plus tires; I got Bridgestone Trail Master. I love how they look and hopefully will serve me well in the farm land and mtns of Western MD. I also need some shims, but first I had to buy the metric feeler gauges to zero in on the correct sizes. Man this free bike is costing some money. I hope it pays off with some exciting future rides in the hill country!
     
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  10. Palmer650#2

    Palmer650#2 Member

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    Today was a good day! I got a nice Birthday present in the mail, shims from Hogfiddles have arrived. I installed them and rechecked all clearances - all in spec!!

    What is the best way to remove the old valve cover gasket? This thing doesn't wanna come off, it's like it's deep fried crispy!!
     
  11. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Plastic putty knife or a bit of hardwood cut into a wedge. Scrape, scrape, scrape, but don't gouge the cover.
    This stuff helps a lot.
    [​IMG]
     
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  12. a100man

    a100man Well-Known Member

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    If its still on the cover try dipping in a tray of brake fluid to soften it up. might also take teh paint off though so make it shallow..
     
  13. Palmer650#2

    Palmer650#2 Member

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    Thanks guys! I ended up using Permatex Foaming Gasket Remover. It worked ok, but it was the best I could find. Next time I will either soak the gasket for a day or two or get something stronger.

    The good news I got the new gasket installed and Valve cover is back in place and looking very clean. Underneath that cover are 8 very happy clearances! I gapped and installed new spark plugs too.

    Next step: install new carb boots and carb rack which is zestfully clean with all new o-rings, float seats, needles, & bowl gaskets thanks to Xj4ever! Carbs are bench synched, wet float heights set, and ready to fire up.
     
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  14. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Brakes. Rebuild them if you haven't already done so. Stopping > going.
     
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  15. Palmer650#2

    Palmer650#2 Member

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    Thanks K-moe! I took you's guys advise and am currently waiting for my custom fit brake line - Xj4ever sent me a test fit which I mailed back for crimping. I swapped bars for straighter bars and needed to shorten brake line for the flatter replacement MC to the union joint. Brake caliper rebuild complete and the rear pads don't show any signs of delamination.
     
  16. Palmer650#2

    Palmer650#2 Member

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    I installed new carb boots and gaskets last night and am ready to hook up carb rack and new air box boots. Before I get into synching and color tune I have a few questions.

    1. I set my pilot air mixture screws to 2 1/2 turns out. Do they need to be different for a non-YICS 1980 xj650?

    2. Do I Colortune or do a running synch at the first start up? Fingers crossed it starts right up without any high or hanging idle!
     
  17. Palmer650#2

    Palmer650#2 Member

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    Did you find that in a store or did you have to purchase online?
     
  18. rocs82650

    rocs82650 Well-Known Member

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    No. between 2 and 2.5 turns out from soft bottom is the starting point for all xj's.
    Synch first.

    Gary H.
     
  19. waldreps

    waldreps Active Member

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    Actually, according to Len's information (which I've been reading through a lot cause I've got carbs to go through soon) the 1980-81 XJ650's used coarse thread screws for the idle mixture screws and should be set to 1.5 to 2 turns out to start. The 1982 and up XJ650's switched to fine thread screws and should be set at 2.5 to 3 turns out to start. That's assuming the bike has the original carbs and the correct thread screws on it.
     
  20. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    My local NAPA carries it.
     

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