I just got 98, F3 couple of weeks before. Bike was riding real nice for around 100 miles. Previous owner put only 3K miles....so I assume bike is sitting in the garage most of the time. It came to reserve couple of days before and I rode it for may be 4 miles after that. All of a sudden when I tried to start yesterday, it's cranking...but not able to start. Backfiring a lot....with real loud POP sounds....my neighbour came over to see...if some put a bullet on my head :-). Too much backfiring.....fouling plugs.
My guess is: Gas in tank might be very old with some junk in there...when it came to reserve...all the junk went to carbs.
Or the plugs needs to be changed???

I checked the plugs and they are black oily, smells like gas. I think it's running real rich and might be over flooded. I cleaned the plugs and tried...it's trying to start but again same problem. Checked the spark of the plugs...they are not bright blue...but little lean (all of them). Thinking to change all plugs today. I don't know what's wrong at this point.
This is the sequence I want to do....
1. Clean plugs -> Done & failed
2. Replace plugs -> need to do
3. Check spark of new plugs , if still weak then might be coils
4. Plugs fine..then dump the gas from tank
5. Don't want to touch the carbs...it's so tight there...and never dealt with carbs. (last option)

Please advise...if I need to look somewhere else. And also under the tank I found 3 connections going out. Petcock, Over flow black hose and other hose....what is that other hose. Can I just pull them to take the tank out and reconnect the tubes.

Please advise......too bad after riding for two weaks...I have to deal with all this stuff.

 

I'd start by dumping the old fuel and filling up with fresh gas. Also, replace your fuel filter while you've got the tank off. It's a 10 minute job.

Before you replace the plugs, make sure you have fresh gas in the carbs, or they'll just foul again. You can drain the float bowls and let them refill, then drain them again to make sure it's fresh gas.

 

I never took the tank off. I found 2 hoses going out other than petcock. One is not connected anywhere and I don't know about the other one. Can I just pull it off. And also is there any online pic's or manuals available.

 

Finally able to make it start. I cleaned the plugs, took the tank off and dumped all gas, drained gas from float bowls, Put new gas...that's it. It started right away. I can return the plugs now...save some green....these are pretty expensive.

This is real cool site shows how to clean carbs ....
http://thegsresources.com/gs_carbrebuild.htm