It's time that we got some "hard data" on the whole "Don't leave your petcock in the PRI position" ... position. :roll: I wonder if we're all being held hostage by a problem that existed mostly in bikes from the 70's and earlier....
I've tried to think back over 2 years of GStwin.com history: hundreds of contributors, tens of thousands of posts. I've had a hard time pulling up very many (any?) "confirmed kills" on this problem, but of course my mental filing system isn't foolproof....
How many of you have personal experience with the float valves on a GS500 sticking open and draining some portion of the fuel from the tank?
If this has happened to YOU, please describe the situation. Did the fuel exit the carbs via the airbox, and glug out through the airbox drain hose? Perhaps it drained forward rather than back, and filled in a cylinder that had come to rest on the intake stroke? Maybe it went both routes?
Details! We need details!
If sticky float valves ARE a real problem, then it's good for us to know about it. But I'm betting that the percentage of GS500s that have leaked fuel on the PRI position is lower than ... what ... the percentage of Americans with (diagnosed!) cancer.
Maybe that's not saying much anymore? :dunno:
I had that problem on my left carb and it's all because of O-rings. They had deteriorated to the point of not holding the valve seat in place, and as you can imagine, the float just can't push the needle valve AND the valve seat back up to stop the gas flow. The excess gas did exit thru the airbox drain but one time when I forgot the bike on PRI there was gas everywhere. And of course this gas got ignited somehow and made quite a mess on the left carb (<=understatement).
The way I see it, if your bike is working perfectly (namely the O-rings are good and holding) there's no reason why you couldn't leave it on PRI all the time. But that might be just asking for trouble...
Quote from: KerryI wonder if we're all being held hostage by a problem that existed mostly in bikes from the 70's and earlier....
In 30+ years of riding and more than a few bikes, I had one personal experience with stuck floats - on a two week old 1975 Yamaha RD350 that had about 1000 miles on it - filled the crankcases up with gas and ended up stuck in the middle of nowhere until a dealer came and picked up the bike - Never did figure out what caused it - did not happen in the following 20,000 miles on the bike - it takes a long time to get that much gas out of a two stroke crankcase.
On the three suzuki bikes that I have had with the vacum petcock I have never had a reason to leave the bike in prime.
Hi guys, my first post , but I have already had the benefit of reading the tech details of this board and appreciate the insight that I have recieved.
I don't know if it was from stuck float valves (am going to try the float level test shortly...) but I once rode my bike in the PRI position, shut the bike off, and worked for 8 hours. I started my bike while standing to the right of it, and a blast of fuel hit my leg from the right cylinder head gasket area!! After this, the bike passed a leakdown and compression test, but I do believe that there is truth to the problems created by leaving the petcock in the prime position.
Just an update to this olllld thread, my GS (after hibernating for a few months) drained it's gas tank on me over the past week or so, and started puking oily gas onto the freeway as I was headed out of town for a ride this morning. It has never given me any problems after pulling the stock frame petcock almost right away (when I got it new, it struggled on the open road).
I'm adding a simple on/off valve in between the carb inlet and the prime out on the tank.