I cleaned my carbs and replaced the air filter today.  My bike has new spark plugs (3 weeks old), and a new Yuasa Battery (also 3 weeks old).

But the damn thing will not start up!  It cranks and cranks with no success...

Any Ideas?

You can eliminate the carbs by shooting starter fluid into the engine and cranking..

If it fires on the starter fluid, then its a carb problem...
If it does not fire on the starter fluid, then its probably a spark issue..

Just dont shoot starter fluid *as* you crank.. If it backfires, the can of starter fluid can explode in your hand..

Just shoot some into the air intake on the carbs and crank and see if she fires..

Set to prime, make sure there's gas in the carbs...
Check the spark from the plugs...

:dunno:

...just did the spark test, and the plugs are good

is there something I am overlooking?

QuoteYou can eliminate the carbs by shooting starter flud into the engine and cranking..

EASY EASY EASY,   on the starter fluid. its very volitile, alittle goes along way. very easy to use too much and can be very painful to you, your bike and your wallet.

What do the plugs look like? Are they soggy after trying to start it?

Do you have a fuel filter spliced in the hose between the petcock and carbs? You could look in there to see if fuel is getting to the carbs.

plugs are new and look new...

no fuel filter here..

Pull them out after trying to start it a couple times. If they are still dry, there's no gas getting into the cylinder, and probably not into the carbs either. Sweet avatar, btw.

gonna try starting my bike again...

the engine is still cranking- but i dont want to kill the battery.  I'm not sure I trust the guys at my local suzuki dealers service either...

the third to last time I tried to start my bike today the engine cranked and fired for a half-second.  That was the best I heard from her today...  

did you put the vacuum line from the carbs to the petcock back on?  cause it really sounds like you are not getting fuel

Prime candidates are:

1. The valve on the bottom of the tank is in the off position - no gas will leave tank (Did this one myself)

2. Lines from tank to petcock hooked up incorrectly or kinked when you put on the tank - check them.  If you do a search Kerry has posted diagrams and directions a number of times.

3. Lines from petcock to carbs hooked up incorrectlly - most likely candidate is the vacuum line

4.  You are low on gas and /or not putting it in prime to fill the float bowls - check that there is gas reaching the bowls by loosening the drain plugs - gas leaks out fine - no gas, add a little gas to the tank - and fix the lines![/list:u]You said that you had spark so will skip all the clutch switch/sidestand switch/kill switch stuff.

IT STARTED!!!!!!!!!!!!!

After letting it sit for six hours (while I was at work), I came home, took a screwdriver to check the carb drain screws , and yes, there was gas in the carbs that leaked out.   Then I was able to start it!

I ran it for about ten minutes, but it was firing weird- making popping sounds at first, and when I took it for a spin around the block, it lacked throttle response unless I switched it to prime (for a few seconds) while riding.  Then It died, and wouldn't start again!!  :x

What is the problem?  Why can't this f-ing bike be reliable??

that definitely sounds like a clogged jet or improper jets all together...when I went into my shop I got the wrong jet type, still 125mm but had a different non-slotted head and my bike would start and run but then died and would not start again until it cooled off....88% sure this is your cause of frustration...While you got 5 minutes before ripping the carbs off again check the float heights

Double check for the o-ring seals atop the carbs and MAKE SURE THE LINES are not dry rotted...When I first got my 91 GS500E the lines were original and had been in storage for 9 years....needless to say something crawled up the gas line and restricted flow, or the lines shrinked

Ran it again a few minutes ago....

The engine is making popping sounds and several times while riding I was forced to switch it to prime in order to get throttle response and keep it from stalling...

I must have missed something.

So, if you leave it on PRIme does the bike run decently?

I have only been leaving it on prime for 30 seconds at a time.. Yes, it makes it run correctly.  But I don't want to leave it on prime; wouldn't that flood the engine?

No, it won't flood the engine - not while the engine is running anyway.

Using PRIme is just like having an old-style ON/OFF petcock set to the ON position.  The only real "danger" is leaving it set to PRIme when the engine is turned off, and only if one or both of your float needles are stuck open because they're worn out or because some grit got in there and won't let them close.

Now, since PRIme works OK ... how much gas did you say you have in the tank?  If you have plenty, then maybe the ON hose from the tank is blocked.  Does the engine run OK in the REServe position?  There is nothing wrong with the RES hose, because that is the one being used by the PRIme position.  If the engine doesn't run well in the REServe position then I suspect either a bad diaphragm in the ON/RES/PRI fuel switch, or a vacuum leak in the hose (or connections) between the switch and the carburetor.