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78 GS550 fuel in engine

  • Thread starter Thread starter DumbGenius49
  • Start date Start date
D

DumbGenius49

Guest
Hey all,

My carbs are definitely having a problem as the fuel is making its way into the engine, quickly. I removed the carbs, checked everything withing the float bowls, all of the jets are clear and the valve needles look good. The need valves are the problem I'm thinking. They don't look worn at all but the springs seem very weak when the floats come into contact with them. I came here for a second opinion. Do you also think that it's the needle valves?

For reference, I put the carbs back on and placed the petcock on prime for a minute, and after that minute fuel started to come out of the bottom of the engine because I had all of the oil drained and the oil pan bolt off.
 
Could be the float needles but it could also be that the floats aren't floating anymore. Easy way to verify that is to drop the floats in a jar of fuel and observe. Another thing is the o rings on the float valve seats could be letting fuel past.

Main thing is to make sure you have everything clean - remove the float valve seats, inspect the o rings, check the floats, etc and try it again.
 
I went through the exact same thing. Left my petcock in "prime" position one night, and in the morning woke to find my entire tank flowed through my carbs and filled my crankcase, ultimately spilling gas all over the shed floor. It had filled the engine to the brim with gas. Make sure your floats aren't stuck, NEVER leave it parked with the petcock in "Prime" position. Of course, you'll need to do an oil change now, which is stating the obvious I know.
 
The '77 has VM carbs, if a bad petcock causes the carbs to overflow it should come out the float bowl overflow tubes under the engine, it should NOT go into the crankcase like the later CV carbs with their EPA mandated lack of overflow tubes.

Either way you need to do something about the petcock.
 
I had fuel leaking from my carbs into the motor without much if any coming out the bowl overflow. I believe the bike was parked on a slight hill with the front end lower than the rear.

When I checked the float valve needles, I couldn't see any marks on them. I could feel a slight groove where they sit in the valve seats. Swapped out the valve needles for these from Z1 and it fixed my overflow issues. Well, except for one carb until I discovered I hadn't fully tightened the valve seat down.
 
How long have those Z1 needles lasted you so far? I seem to have the same problem as you, I can't really see anything on them but i can feel a groove where they seat, so I would like to get needles that are worth while.
 
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