‘93 stock GS carb setup/testing

[FirstGS500E]

Hey riders!

Columbus, Ohio ~900' elevation.

Just getting around to sprucing up an old 93 GS I picked up a while back.
Details of bike:
-1993 GS500E
-fully stock (no intake/exhaust mods at all)
-carbs are stock jetting (30 and 122.5 I think?)
-Floats set to 14.6mm
-mixture screws set to 2 1/4 turns out.
-bench synced using smallest needle gauge I have.
So, I removed the carbs cleaned them thoroughly and new gaskets/orings. Drained/cleaned tank and used fresh gas. I inspected the petcock and seems to be working properly but will get to that in a minute. When I put the bike back together I turn the key and it would not fire. If I open the gas cap and stick a paper towel tube(perfect fit)in and pressurize the tank by blowing on the tube it will start to fire until I remove pressure from the tank then it dies.

What's is a sure test for frame petcock?
Any suggestions on what my next step is?

Thanks guys!

[The Buddha]

You route the hoses right ? Looks like your carb vent is plugged up - upper rear T in the carbs needs to be open to atmosphere.
Cool.
Buddha.

[FirstGS500E]

Thanks for chiming in! Not sure I have another upper "T". Thought the upper T is for the vacuum to petcock. I pulled the carbs off again. Checked everything out. Running a bottle and line straight to carbs it fired up, idled for a bit but wouldn't go over 4K without dying. Put my hands over the carbs to restrict some air (air box was removed for working on it) seemed to idle better and then it would rev up to higher revs. Little rough but better. Hoping it was due to no restriction from sonic. Thought all was good so put her back together. Once again, won't start without adding pressure via paper towel tube.

Thanks for any assistance with this ol girl.

[mr72]

If you have connected a vacuum line from the overflow vent to the petcock then that is your problem. Vac port is on the side of the left carb. That vent needs to be open and not facing the front of the bike.

[FirstGS500E]

I think I may know what you're saying. (An example pic would be cool though)

I will pull tank off and look at mine again after I get home from work.

Thanks again!

[FirstGS500E]

Sonovabiscuit! It just dawned on me! Really looking forward to getting in the garage!

[mr72]

Real quick:

- there's a hose routing diagram that is posted about 10,000 times on this forum. You need that.
- If you put the petcock on PRI like you should to get fuel into the carbs to start, then it should start and run fine regardless of the health of the petcock or fuel flow.
- If you have effectively plugged the carb overflow vent, this will prevent fuel from flowing into the carbs. put hoses right and you should at least have a chance of it running.
- stock jets are 37.5/122.5 . it should run just fine on these jets, maybe idle a little bit lean, but 2-1/4 turns should work ok.
- go read the blog post in my signature.

[FirstGS500E]

Thank you for that write up. Bike wasn't fully assembled when I began. RTFM is real! Great info in the link! Hoses are correct now. Started at high idle then settle, died soon after. Fuel is in the floats. Still working at it as I scratch my head.

[The Buddha]

If it dies as its warming up and will start back up when cold you may have
1. Tight valves. Revving it will keep it running and once warm it will run. But adjust them to spec.
2. Be super rich. Revving it will keep it going, but once warm still will want to drop lower lower and stall when throttle is blipped. And look for white smoke once it clears all the plugged up soot. However this is unlikely with floats set at correct and air screws at 3 turns out. Because that idle-low throttle is controlled by pilot jet and a 37.5 or even a 40 is too small to let it get rich enough to stall.
3. Have a ignition crank trigger go bad, usually it will lose spark in 1 cyl. Hitting that part with cold air spray will revive it a few seconds and it will die again.

Cool.
Buddha.