So, I have been trying to get my wife's 1994 GS500 in running order the last few weeks.  Got a new job over the summer so the project took a back seat (much to her dismay).  But now I've got it all back together.  Everything is looking really good but I am having a carb issue that I think I have figured out but want some other opinions.

Currently bike is running on 1 cylinder only (right side).  The left side plug is sooty and wet with gas when checked.

I ruled out ignition by checking spark, and swapping coils and plugs.  The dead cylinder (and fouling/running rich) always remianed on the right.  I even checked balance with carb sticks and it seemed spot on.

So, I decided it was time to admit defeat and remove the carbs from the bike to get a better look at them.  So I started up the bike to run it out of gas (makes it less messy to remove them) and proceeded to clean up the tools I had out.  While it sat there and idled it started running better and better and soon I could tell the left side was running great.  I could unplug either spark plug and bike would run on 1 or the other cyclinder meaning the left side had corrected itself!

So, my idea is that the float height is set too high such that when the carb bowls are filling with gas the left side gets too much (fills to high) and it is fouling out the plug and basically just delivering too much gas to the left cylinder.  However, once I remove the gas supply, as the fuel level drops to the appropriate level the carb functions as it is supposed to and I get great running.

Does that make sense?  Or am I missing something else about the carb circuits and what would be working in the low gas condition? 

I will check the float heights before removing the carbs (which means filling them up with gas again!!) with the tube attached to the drain trick but wanted to see if someone could second my opinion or add one of their own.

Thanks for the help.

Kyle

+1 on the U-tube drain float check.  That will give you direction.  Because of how/when it happened, I would be inclined to think along the same terms as you did.

As a side: What made you drain the remaining gas by 'running it dry' rather than the carb drains?  I mean, you would have to use them anyway to check the float height right? ... Regardless, it gave you light at the end of the tunnel when it started running on both cylinder I'm sure!

- Bboy

I guess I like the feeling sucking in exhaust fumes gives me? 

Seriously though, I am not sure why I did it that way other than I didn't have the drain hoses easily at hand and it was already idling away so I just let it go.  Plus, I didn't have a clue about what the problem might be at that time.  The drains  do work as I had opened them to check if float bowls were filling with gas (they are).  Just wish I had had the idea of it being float height before I had done it.  It came to me later when I was thinking about the problem.

Not sure if I will get to it until the weekend so if anyone else has any ideas let me know.

I had the issue that one of my cylinders would not run when the bike was on choke.  I then realized that the little jet that is inside the bottom of the plastic float was completely blocked.  Once I cleaned it out with a guitar string, everything worked perfectly.  At least it's something to check.

Float height sounds like it's your main issue though.  If you can't get it worked out by adjusting the tab on the float, then I would suggest buying new needle valve sets.  OEM sets work great, K&L aftermarket sets do not work well.  I suggest buying from ronayers.com.

Quote from: mankyle on October 02, 2012, 10:20:15 AM
I guess I like the feeling sucking in exhaust fumes gives me? 

Seriously though, I am not sure why I did it that way other than I didn't have the drain hoses easily at hand and it was already idling away so I just let it go.  Plus, I didn't have a clue about what the problem might be at that time.  The drains  do work as I had opened them to check if float bowls were filling with gas (they are).  Just wish I had had the idea of it being float height before I had done it.  It came to me later when I was thinking about the problem.

Not sure if I will get to it until the weekend so if anyone else has any ideas let me know.

Check your floats, that they do not leak, and that the metal tabs where the needle valve metal spring loaded tip rides, are not worn (you'll see it with a strong magnifying glass ) - bending the metal tab any appreciable amount to compensate for wear will put a side load on the needle valve, and may cause it to not seal like it should.

I have a '95 gs 15000 mi. - couple weeks ago it developed a minor flooding problem, drain/clear tube method indicated high fuel level both carbs, caused in part by worn float tabs.