Hi All,
I have a 1991 GS500 that I have been trying to get running for my wife and I am stuck. I have cleaned the carbs, adjusted the floats multiple times (and verified level with tubing on the bike). However, the bike only wants to run on 1 cylinder until it is almost out of gas. I know this because I currently have a funnel as a gas tank so I can get to the carbs easier and as luck would have it this may have revealed a clue to the problem (I think).
When the funnel is full up (and the carbs too, at least by tubing on the drain) the bike will run on only 1 cylinder. However, once about 75-80% of the gas is gone (my best guess), all of a sudden the other cylinder roars to life and the bike runs great until it runs out of gas. I have tried cleaning the carbs a couple of times and all passages seem clear (at least I can spray carb cleaner into them and it comes out somewhere else. I can't find an issue with the carbs but maybe someone here has a better idea of what I should check. My thought is that a passage is blocked somewhere but which one? Or, maybe my float level is wrong but again it looks OK both by measuring off the bike and by tubing on the bike.
I have swapped coils, plugs, etc and the problem stays on the left side so I am convinced it is carb related. Also, its been a while since I worked on it but I don't remember the plug being soaked with gas so I really think it is lack of gas getting to the cylinder, not a flooding issue but that is a guess and I suppose it could be either.
I have had these carbs apart numerous times and everything seems OK. I did open up the mixture screws so they have been both set at 3 turns out and messing with them doesn't seem to help. Would this be the symptoms if the float height was too high?
Any ideas?
Thanks
Since you don't have the tank on, do you have the vacuum line from the carbs capped off?
And when were the valves checked last?
Yes float too high could do this.
Cool.
Buddha.
Good question about the vacuum line. I am not sure I did when first testing (I think I went right from funnel to carb fuel hose) but I know for some of the testing I added the petcock to the mix and it would have then been connected. I did also try it with the tank on a few times but when everything was hooked up and gas in the tank it only ever ran on one cylinder until I shut of the gas at the petcock and let it run dry. Then for the last minute or so it would run on two cylinders like it did with the funnel.
As for valves, I am pretty sure they were checked 4 or 5 years ago when the bike was last running. It is on my to do list but how would valve clearances affect the running at different fuel levels? I agree they need to be checked but not sure that is my issue since the bike will run absolutely great when the gas is low.
I guess my next step is trying to lower the float height but I seem to remember that the tang was bent pretty far already and not sure I can move it much more. Any tricks?
Thanks.
Kyle
Seemed to have fixed my problem. I am guessing I just didn't clean the carbs well enough the first time or maybe got something in them after cleaning.
Anyways, this weekend I took the carbs off the bike and opened up the one that wasn't working (I thought) and cleaned it all out including running a small brass wire though all the ports etc. Put it all back together, and it was still running on one cylinder. That is when I realized it was the the side with the carb I just cleaned! I cleaned the wrong one! Where it had been parked for the last 3 years I knew it was the outside carb that wasn't working. However, at some point I had turned the bike around!! :cookoo: Never fired it up before removing carb because didn't want them full of gas.
After some cursing and nice long break I took the carbs off and cleaned the other one. Checked both float heights and they were fine so I buttoned them back up, put them back on the bike and it fired up and ran ON BOTH CYLINDERS!!! After alot of smoke and a little backfiring I even got to run it up and down the road a bit and it seems to run well. Guess I need to re-line the tank now and hopefully have it on the road for my wife next spring.
One question. It idles awesome and has good throttle response. However, when idling, if it starts to run out of gas (I am using a funnel on the gas line as a tank right now), the revs jump up really high (like 3,000 or so) and nothing can be done except to shut it off. Is this an issue with a cause and fix or just a good reason to keep gas in it?
Thanks,
Kyle