Runs Great, Wont Start, Help!

[Scott Raznoff]

So I bought a 1982 GS650GL with 13k miles from a guy here in town about 2 weeks ago. This is my first bike, rookie story...
The thing runs and idles great, but after sitting for over an hour or so it just won't start. The starter spins, but no combustion sounds at all. I bought a trickle charger/tender to keep the battery fresh. The plugs look great, and have great spark.
I have no real experience working on bikes, but have ordered the manual (hope to get it in the mail any day), and wrenched around on it a bit.
I have managed to get it started by taking off the cover to the air filter and 'priming' it with butane. Once started, it runs awesome and even will restart easily if it is only off for a few minutes.
Originally I thought that I had Petcock problems, but i took it apart, and everything looks real healthy. The diaphragm moves when i suck on the vacuum tube, the filters are clear, rubber is shiny, ect.
Then i tried cranking it with the tank off. I held my thumb over the vacuum tube, and there is a very weak suction when starting. I compared this to when it runs, and the suction is much stronger when it runs.
I am thinking there could be a leak somewhere in between the engine and the carb, but I am not sure.
I would appreciate anyone who could help me troubleshoot this thing so I can get it on the road reliably.
I am really intimidated by taking the carbs off/apart to clean them, there are so many peices i am not sure if i would ever get them back together. but if it's the only way....

 

[zacheriaj]

The vacuum increases with engine rpm. The vacuum (just like in a car), is caused by air intake into the engine. So what you explained about that is normal. Check your airbox seal and intake boots though. The plugs may spark nice when outside of the engine, but in a compressed air environment, a spark that could normally jump a couple inches, can now only jump half a millimeter. So make sure the battery is good. Check your compression. When things warm up, they expand. which could cause you to lose or gain compression by a miniscule amount. There is actually another post a few topics down with the same problem. take a look at that one.

 

[Suzuki_Don]

Try this link and you will find the Suzuki Factory Manual for you model.

http://www.mtsac.edu/~cliff/storage/gs/GS650GManual.pdf

 

[Scott Raznoff]

Thanks!

Thanks!

Thank you for the resources, I have been able to coax it to life twice today without using the butane. I haven't exactly located the problem, but as soon as this snow clears up I will do some work and see what I see.