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Why are my carbs running over?

  • Thread starter Thread starter dadgummit
  • Start date Start date
D

dadgummit

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'82 gs650 shaft drive. My carbs are dripping fuel into the airbox on all carbs. I've put in new needle valves and seats and have obviously got the float setting wrong somehow. My clymer manual is kind of vague on float setting adjustments. It says 21.4-23.4 mm (.84-.92 in) without the gasket. There is one fuzzy picture of a guy holding a caliper towards the end of the metal on the flat part of the float. My needles are spring loaded and the weight of the floats push the spring down it seems. Do I just let the spring compress by the weight of the float and then measure to the end of the metal bracket that holds the float? In other words just measure it however it sits? Thanks for any advise.
 
dadgummit said:
'82 gs650 shaft drive. My carbs are dripping fuel into the airbox on all carbs. I've put in new needle valves and seats and have obviously got the float setting wrong somehow. My clymer manual is kind of vague on float setting adjustments. It says 21.4-23.4 mm (.84-.92 in) without the gasket. There is one fuzzy picture of a guy holding a caliper towards the end of the metal on the flat part of the float. My needles are spring loaded and the weight of the floats push the spring down it seems. Do I just let the spring compress by the weight of the float and then measure to the end of the metal bracket that holds the float? In other words just measure it however it sits? Thanks for any advise.
Click to expand...
Are you measuring right before the bend in the float metal,the straight part that the pin connects to? It needs to be at eye level and resting on the needle valve.Make sure your needle valve springs are working properly and the float pins are in right.Let it rest however it sits.The picture is difficult to see. Hope this helps.
 
yeah thats were I was measuring. I'll go back through them again. It seems like I had to bend the float tab quite a bit just to get the right? float height. I would guess about 35* down. Is that normal?
 
NewPicture.jpg
 
dadgummit said:
yeah thats were I was measuring. I'll go back through them again. It seems like I had to bend the float tab quite a bit just to get the right? float height. I would guess about 35* down. Is that normal?
Click to expand...

You did something wrong, the tab should be pretty close to straight.

Sometimes the springs in the needles are a little weak. Lower the float until it just starts to contact the needle - don't expect the spring to hold up the float.
 
so, I need to actually measure right before the step on the flat spot? With no gasket? Hey thanks for the picture with the dimension lines!
 
there is something wrong because I can't even get close to that measurement. I can get that much measuring to the flat of the float but not to the step. To get that much I would have to bend the tab even more and I'm at the limits of the tab. I'd hate to think that I got the wrong needle and seat kit. If you can see the picture is this were I need to measure to?
 
dadgummit said:
there is something wrong because I can't even get close to that measurement. I can get that much measuring to the flat of the float but not to the step. To get that much I would have to bend the tab even more and I'm at the limits of the tab. I'd hate to think that I got the wrong needle and seat kit. If you can see the picture is this were I need to measure to?
Click to expand...

Yes, to the step. Seems like you got the wrong needle/seat.

Many of use reuse the original needle/seat unless there is noticeable wear. You might want to try installing some of the old parts to see if there is a difference.
 
I just found this from bwringer:


A couple of things I'd add:

1) Watch out for crappy aftermarket float needles. There's a little spring-loaded nubbin in the center of each float needle where the float tang contacts the needle. On GS carbs, this spring should be strong enough to hold the floats up when the carbs are upside-down without compressing at all.

I've encountered shoddy aftermarket needles that have weak springs, making it nearly impossible to set float height. Just imagine how long it took me to sort out exactly why the &^%$##!!!! my bike wasn't running quite right. Just imagine how far I threw the stupid things once I figured this out. And imagine how I felt when I realized that the only usable parts in $100 worth of rebuild kits were the float bowl gaskets ($4 each at CRC2).

There are some aftermarket needles that are OK, but it's hard to tell until you get them in your hands. (I got a set of high-quality new needles on eBay from a guy in New Zealand, supposedly from the OEM manufacturer.)

If yours have squishy springs, you could try propping the carbs up at an angle so the full weight of the floats isn't pushing down on the springs -- with some bikes this is the normal procedure anyway. I'm not sure how well this would work on a GS.

2) Make sure both halves of each float are set to the same height. This takes a little time and care to get right.

3) If you can find a small sensitive scale (measures 1/10 grams), weigh each float to make sure the foam hasn't deteriorated and soaked up gas. The floats should all weigh the same within a few tenths of a gram. You can also put a little gas in a jar and make sure each float floats at the same height and angle. I've encountered this problem on a car, but not a GS yet. It's worth checking, I think. I used an electronic postage scale.


I've got the squishy spring needles. They compress by half with the weight of the float. I think I tossed the old ones. crap.
 
Hold the float with your hand and don't let it compress the spring.
 
do all bikes have spring loaded needle valves? What is that for anyway? I wonder if I could rework these needles without the spring?
 
I don't know all bikes (I feel like I barely know my own), so I don't know if they all have spring based needle valves.

What needle valves: In conjunction with the float they meter the fuel from the fuel tank into the carbs. When the bowls are full, the floats rise and push the needle valves closed which stops the flow of additional fuel which keeps the carbs from overflowing. As the fuel in the bowls is used, the floats lower, the valves open and fuel flows in until the bowls are full again. This cycle repeats.
 
vents

vents

Mine was doing exactly the same thing. It drove me crazy taking the carbs off and measuring float heights, then watching the fuel gush out again.

Finally, after realizing the flotats worked perfectly on the bench, yet poured fuel out once installed, that I had the float bowl vent hoses connected incorrectly. I had one vent connected to the other.

Took the vent hose right off, as many others here have recommended - end of problem. Pretty easy fix to try!

Later added some routed overtop the airbox as per original, still works well too.
 
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