My 1989 gs500e was starting to run a little rough so I decided to perform a simple carb cleaning.  I recently had gotten a half helmet which allowed me to smell gasoline; my full helmet did not allow this to happen.  I thought that any leaking gas might be taken care of by checking the fuel lines upon reassembly thus fixing the smell and the rough running.  I disassembled everything needed to pull the carburetor and did a thorough cleaning.  I measured the float height as described in my manual and saw that they were out of spec so I adjusted them slightly.  I reassembled the carb and put the bike back together as the sun was going down, and my light was therefore dwindling.  Apparently, something between a puddle and a pool of gasoline had poured from one of the loosely fitting fuel lines onto the crankcase, because when I went to start her up she burst into flames.  By the time I got the pin pulled from the fire extinguisher and was running back toward the bike, the flames were lapping up all around the tank and were head high.  Thankfully I was able to halt the fire before it exploded. 

In the brief yet rapid fire, all of the fuel lines were toasted and the breather box was malformed.   I replaced the fuel hoses with new ones and attached hose clamps to each of the ends to prevent any further leaking.  As a temporary fix I put some pieces of old t-shirt and coffee filters on the carb intakes in place of the now missing breather box.  My motorcycle is my only mode of transportation and I am a student meaning have no money to pay anyone else to fix it.  I have disassembled and reassembled several carbs in my day and once did a complete engine rebuild on a yamaha xs850.  I am as embarrassed about setting this bike on fire as I am grateful to be alive to tell the tale. 

So here's the thing, now when I try to start it up, it sounds like there is no gas.  Yes, I checked the fuel tank and I added another gallon and a half.  Yes, the fuel valve is open.  And yes, I am pretty sure that the fuel and vacuum lines got replaced in the correct configuration.   It makes the jjza jjza jjza sound like it is eager to start, but it sounds just like how other bikes have sounded on the road side when you run out of your reserve tank.  Then it backfires, sounding like a pistol shot.  My neighbors are as over this as I am by now.  Could the jerry rigged air filter be causing this non-starting, backfiring problem?  Or should I reexamine the float adjustment I made?  Or is there something else that I should check?  I didn't make any other adjustments to the carb beyond cleaning it and adjusting the float tang a tiny bit.  Before this whole cleaning, burning, air filter ordeal this bike started pretty easily.  I hope for some useful insight and am willing to take a bit of ribbing for catching my bike on fire as well.  Thank you for your help. 

Appropriate emoticon inserted here. 

I would check to see if petrol has got into the crank case first. Did it sit for awhile before you tried to start it?

Here is your emoticon -

Don't feel bad, I nearly set a car on fire just last week ... if your fire was that bad, to toast lines/airbox, it may have damaged the  electrical harness. Double check , cuz sounds to me like hinky spark, if you've covered all the other things.

I just disassembled the carb again this afternoon, and found the diaphrams to be buckled and warped out of shape.  The floats and all the other plastic appear to be fine, but the diaphrams will absolutely not fit back inside the metal trench where they are intended to rest.  I can't find any on ebay.  My new question is regarding where to look for these things.  Is there some insider shop for buying mikuni carb parts?  Please advise.

Those are good suggestions about the gas in the crank case, and the weak spark.  I plan to do an oil change while she is up on blocks, so to speak.  And it won't hurt to check the juice pulsing through the plug wires.  Oh, and great emoticon.  That is sort of how I looked while running around the fire. 

Also, is it an okay idea to find some aftermarket air filters that fit on the carb intakes to replace the breather box?  I know that the combustion emissions won't  get dealt with in a happy way, but will that affect the performance of the engine?  Will the air filters affect the performance also?  I have never made modifications like that before, usually I strictly do what the books say to do.  Please advise.  Gratitude.

Some non-professional advice, to a non-professional:

at this point, your bike is a mess, because you didnt know what you were doing the first time.
You still dont really know what you are doing, but you have a much, much tougher job now, than you started with.

If you want to fix it yourself (which at this point does not sound like a good idea)
doesnt it make sense to limit "things that could go wrong" to an absolute minimum?
With that goal in mind, it wouldnt make sense to me to put anything on it, except for 100% conformant parts.
That means "stock".

Get it running properly, (if you dare) FIRST.  Then experiment with non-standard parts.