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Thread: '77 gs750 fuel mixture screw is screwed

  1. #1
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    Default '77 gs750 fuel mixture screw is screwed

    I bought a '77 gs750b not running with a spare carb set. Went through the set that was on it and it was pretty gunky. I need bowl gaskets to reassemble. (Partzilla?). So onto the spare set which appears to have been cleaned up but just checking the air and fuel mixture screw settings, I found #1 fuel mixture screw has been broken and some work done trying to get it out (see pic). Any suggestions on getting it out or should I try to spray the correct passage and cross my fingers?
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  2. #2
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    Whoops, its the adjustable air screw on the side

  3. #3
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    Use the EARLY 8 VALVE service manual here. And in the right margin youll see some carb rebuilding tutorials. VM tutorial is what you want to use. If you havent dipped them and done a full tear down and rebuild then dont even bother trying to get the bike running right until you do so.

    http://members.dslextreme.com/users/bikecliff/

    And here is the place for the oring kit. 1 kit does the full rack. also see page 3 and get the intake manifold orings as well.

    http://cycleorings.com/
    MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
    1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

    NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


    I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

  4. #4
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    Thanks on the rebuild advice but I need help removing a buggered up adjustable air screw on the side. I tried turning a well fitted straight slot while tapping on the screw driver to get an impact driver of sorts but I'm just mauling it more.0

  5. #5
    fasteddie313 Guest

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    How about a real impact driver?

    Or put a flathead screwdriver bit in a 1/4 socket on a 1/4 breaker bar and clamp through the whole carb onto the head of that breaker with the bit in the slot in a vice or with a C clamp to hold it down.. Sometimes I like using a ratchet or channellocks on a screwdriver so you can really put pressure with one hand and turn with leverage with your other hand..

    Try applying some heat maybe.. let a mix of 50/50 acetone and tranny fluid sit on it over night.. Try turning it to the right and to the left to get it moving..

  6. #6
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    Is that an Ez Out or drill bit broken off in the center?
    Alan


    Weaned on a '74 450 Honda
    Graduated to an '82 GS850GL
    Now riding an '83 GS1100GL
    Added an '82 GS1100GL

  7. #7
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    Its gonna look like crap, but your best try would be to use a dremel and cut a slot down the tower and make a new slot into the screw. DONT hit at it with an impact...the threads arent strong enough to take that kinda hit!!!

    Once its reslotted, heat it good and soak oil to it and heat it again to help wick the oil in. Add more oil and let it set to seep the oil in real good. When it moves a little work it in and out..in and out..in and out to work more oil in and grind up the corrosion. Back it out a little more each time and eventually you may be able to work it out. NEVER use EZ outs on a bike ..anywhere!! They suck and break off easier than they extract bolts and once they are broke off in nthe hole your headed for a machine shop.
    MY BIKES..1977 GS 750 B, 1978 GS 1000 C (X2)
    1978 GS 1000 E, 1979 GS 1000 S, 1973 Yamaha TX 750, 1977 Kawasaki KZ 650B1, 1975 Honda GL1000 Goldwing, 1983 CB 650SC Nighthawk, 1972 Honda CB 350K4, 74 Honda CB550

    NEVER SNEAK UP ON A SLEEPING DOG..NOT EVEN YOUR OWN.


    I would rather trust my bike to a "QUACK" that KNOWS how to fix it rather than a book worm that THINKS HE KNOWS how to fix it.

  8. #8
    Nessism's Avatar
    Nessism is offline Forum LongTimer GSResource Superstar
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    First thing to do is clean some of the crud out of that hole so you can see the slot. If the slot is beyond help then your options are to do as chuck suggests and cut a new slot or to drill out the screw. There was a nice thread here recently where guys offered suggestions on how to get such buggered screws out. A good suggestion was to drill a hole in the screw and then drive a torx bit into the hole to get a better grip on the screw. Use lots of heat and PB Blaster or similar to try to get the old screw to loosen up.

    Good luck

  9. #9
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    Thanks everyone.. I'm loving this site (I 've been riding and wrenching for 46 years using manuals and enlisting some friends but now with the internet I've gotten so much help on forums for my old bikes - cb750, xj550, xvz1200, and now these two gs). I know there is limited thread length and used wd40 but was looking for the best solvent to attack that crud. Yes I thought heat but wanted to confirm that would not bind up the brass and aluminum. And I've done the torx trick, that will be last (was hoping someone might make an oversized thread mixture screw if I get to drilling). Yes I tried working it in And out. And yes I've done the dremel slotting before and that will be next after some solvent and heat and a few more tappy turns And hand pressure using a wrench to turn the screwdriver. And no not an easy out or drill bit broke in there. Can anyone point me to that one thread on buffered mixture screws?

  10. #10
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    Haha, I couldn't wait till the morning and went downstairs. I tried to look close with a magnifier and that screw is buggered deep into the recess. And it actually looks like the factory scribe Mark impinged on the threadbare perhaps causing some of the resistance.. I used a dental pic trying to clear it and left it with a drop of chem dip mixed with nitro oil (ancient product for cleaning guns). Yesterday I could see the screw tip through the air intake bore... Comparable to the others and I was able to shoot some carb cleaner though like the others so it may well be close enough and I'm gonna try running it before drilling or dremmel. Part of my post was to see if there are ways to compensate for that mixture screw being slightly off.

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