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1978 Suzuki GS750

This is a discussion on 1978 Suzuki GS750 within the Technical forums, part of the Caferacer.net Forums category; So this is a second post about my bike that I just picked up. The first was in my original post when I mentioned it ...

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  1. #1
    Senior Member The Chief's Avatar
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    1978 Suzuki GS750

    So this is a second post about my bike that I just picked up. The first was in my original post when I mentioned it and it just kinda of took off from there with everyone trying to help me troubleshoot it. Im just moving it to this section so that its correctly posted.

    So I picked up this Suzuki GS 750 for 300 bucks. What you see is the way it came, I havent done anything yet to it. The seat in the pic is for a Ducati monster, that I had laying around from another build and I just through it on to see what it looked like. The bike didnt come with a seat. I snagged it up cause the tank and fender are in show room condition, no dents, dings or scratches. It wouldnt start and had no spark. I since have replaced the coils, plugs, and plug wires and now have spark. The bike still wont start, its trying but its just popping and chugging. So now im going to move to the carburetor tomorrow and clean it out completely. I fixed a couple vacuum leaks on it which gave it a little more encouragement to start but not enough. On the bottom of each of the carbs is a hose fitting, is anyone familiar with this particular carb? Should those be capped or left open?Name:  photo(5).jpg
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    Last edited by The Chief; 02-16-2014 at 08:27 PM.

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  3. #2
    Senior Member hillsy's Avatar
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    The fittings on the underside of the float bowls are overflows. From the factory they had hoses on them that ran down between the swingarm pivot and the gearbox.

    You don't need to plug them, but putting some hoses back on them would be a good idea.

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    Senior Member The Chief's Avatar
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    Aaah Ok that makes sense! Thanks! My yamaha didnt have those so I was curious.

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    Senior Member The Chief's Avatar
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    Ok I pulled the carbs and they look like they have recently been gone through. They were very clean. I did notice that it was re-jetted, so at some point someone was thinking when they put the air pods on. They put 105 Mains versus the stock 102s and they put in 17.5 slow versus the 15 stock slows. I really stumped...these carbs are very clean, no clogged jets or anything......Ideas??Name:  1.JPG
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    Senior Member hillsy's Avatar
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    Depends on your definition of clean - they look quite dirty to me. Look at all the slime that's on the floats.

    And the biggest problem is the areas you can't see - all the passages behind the jets easily fill with gunk and the bike will never run right.

    Carb cleaner and compressed air are your friends here - you also need to remove ALL the jets (including the idle jet - the one inside the float bowl gasket at the front of each carb. Be careful as it has a tiny spring, washer and o ring behind it). Pretty much everything brass comes out.

    But the brass tube that sticks out of the carb base doesn't come out - you need to make sure it is clear as well as the corresponding passage it goes into in the float bowl. A piece of wire off a wire brush pushed into the end of a matchstick makes a handy tool for these places.

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    Senior Member nicebikemate's Avatar
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    Lol, i'm a grotty bastard and I still wouldn't call those clean. Careful with the carb cleaner as it's pretty nasty stuff and while i'm not sure if it'll damage the floats or not, i wouldn't risk it.

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    Senior Member hillsy's Avatar
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    Also, this $20 thingy is great - a bit of vinegar and a few minutes…..






  9. #8
    Senior Member The Chief's Avatar
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    Quote Originally Posted by hillsy View Post
    Also, this $20 thingy is great - a bit of vinegar and a few minutes…..





    Im not getting any combustion at all. I can get a little bump if I give it a shot of starting fluid but it wasnt much. Im going to pull all brass like you said and clean them as I didnt do that yet. Whats that thing you have there?

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    Senior Member nicebikemate's Avatar
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    [QUOTE=The Chief;285492]Im not getting any combustion at all. I can get a little bump if I give it a shot of starting fluid but it wasnt much. Im going to pull all brass like you said and clean them as I didnt do that yet. Whats that thing you have there?[/Q

    Ultrasonic cleaner.

  11. #10
    Senior Member The Chief's Avatar
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    Hillsy,

    I just pulled all the jets and brass fittings. I tried that trick with the copper wire, that works really well. No clogged ports on anything, no corrosion or any discolored pieces. I can see light through all the ports on everything. Cleaned the grime off the floats with Sea Foam. Which direction should I go in now? Should I put stock jets in?
    Last edited by The Chief; 02-17-2014 at 05:26 PM.

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