I honestly cant remember if I've even posted here yet (been reading a lot though) so I'll do a quick intro post too... If you just want to get to the trouble shooting skip down to *the bad*

I bought a 01 gs500 with 17,000mi at the beginning of the summer for $1300. It was owned my a honda motorcycle mechanic and was running great when I got it. However he had restored it - it had sat outside under a tree for several years. Gas tank has been kremed, carbs re-jetted (or at least tuned - there are spacers under the top of the needle), and it has some very strange AL canister exhaust. I added a kat rear shock, ebc pads, and sport demon tires. Everything was going great all summer...



Then about a bit more than a month ago I went down - lowside at 20-25. Scratched up the muffler, engine case(little black suzuki plate came off), and cracked the plastic around the gauges some how. But I was ok, and everything still ran/road normal.

Two weekends ago I had some friends come in town and we road a total of 17 hrs in two days (dragon and devil's triangle area). The day before the ride I went out to my GS to start it and as soon as I hit the start button, it just killed the electrical system as if the bat was getting a bad connection. The battery was so dead it couldn't keep the bike running after being jumped?! What's really weird is that I had road it just a few days before and it never even hesitated to start?? After a bunch of trouble shooting I through a new bat in it and it never gave me another problem through the weekend...

*the bad*
Until the last 3 hrs of the ride. We stopped at an overlook for about 15min and when I got back on the bike started right up, but as I was riding off it backfired into the airbox - at the time i didn't know what happened, it almost sounded like some thing broke. But it seemed to be riding ok so I continued on till the next time we came to a stop, the bike idled really ruff and would die after about 10 sec. Free reving it caused it to back fire on decel. This kinda concerned me so we stopped and let it cool down. It seemed slightly better, so we continued on - and it ran fine under normal driving conditions, but the idle got worse and worse till by the end of the ride every time I clutched in it would die. It was dark when I got home so I just parked it and went in.

About a week later I decided to go ride again. First thing I noticed was a crack on the end of the muffler where the exit is?! I didn't think it back fires THAT hard! But anyway it took a while to start - ~15 seconds on the starter (not normal). I road down the street to get gas, and it seemed to be running worse, backfiring a lot on decel and it died at the pump. I put gas in it, and it seemed to get WAY worse. I drove down the highway for a minute and it wouldn't go faster than 70! Different throttle positions didn't seem to make much difference. So I immediately headed home.

First thing I did was pull the plugs. Left one looked ok, right was black but pretty dry. I drained the fuel bowl and opened opened the manual fuel chicken trying to freeup anything that might not be letting the needle seat. I pulled the tank and carbs and took the right one apart. Everything looked pretty clean except for some sediment/rust in the bottom of the fuel bowl. I put it all back together - replaced the fuel lines and filter. - It runs slightly better (i think) Still won't idle, still backfires a lot - at low speed in the intake, high speed decel in the exhaust. When I accelerate through first it seems to go in and out of power. And even while cruising I can feel it surging. That crack in the exhaust is turning into a hole...

So i have no idea what is going on. This is my first bike and first carb vehicle - I'm good with cars, but I know very little about bikes... Help!

Thanks,

-Matt

(sorry this post is soooo long, I wasn't sure what details are important and what might be related...)

any ideas? I'm getting desperate..

Originally I would have said the Kreemed tank was flaking off and clogged the carb. But you did say they were cleaned...... Could the float bowl be sticking? And have you checked for spark in the right side?  Maybe something got bumped loose around the ignition on the right side (unlikely though).

When you let off the throttle after hard acceleration, does the bike go:
(1)   "Rrrrrr*pop*pop*pop*rrrrrrrrr*pop*pop*pop*...etc"?
or
(2)    "RRRRRrrrrrrrrrrrrrrrr......*ka-POW!*"?
or
(3)     "*ka-POW!*rrrrrrrrrrrrrr....."?

number 2 haha.

I don't know much about carbs - but it should be pretty obvious if there was junk in there causing issues right? I didn't have a can of carb cleaner to blow through all the passages, but there wasn't any thing where the needle seats. How would I know if the fuel bowl was sticking? It seemed to operate smoothly. Although the float seal did have a slight divit where the rubber seal meats the seat- didn't look bad though. I guess if its not seating fuel bowl over fills and floods that cyl?

Thanks for the replies 

I think, and I could be wrong about this, but I think you have an air leak somewhere. Hard starting, won't hold an idle, but your carbs look clean on the inside. And, from what you've said, no fuel starvation.

Here's a video how to check for air leaks.

http://www.youtube.com/watch?v=XzjSEYB9RDU

And patch that hole in your exhaust.

.... and get a manual ....

i've got a manual  Or at least a pdf of it. With out it I wouldn't have touched the carb haha - but it didn't tell me a whole lot on troubleshooting besides naming all the parts and telling me how it worked.

It was only hard to start once, and I would have thought pulling the carbs and re-seating all the couplers after would eliminate leaks. Also I would think an airleak would make it run lean right? The plug seems to indicate it running very rich (being black)...

but I'll test let you guys know anyway, its worth a shot.

well fwiw if my bike gets a dead dead battery, it wont idle very well until ive ridden about 5 min or so, and takes a little bit to charge back up. you may also of turned the bike off to far that one time and left park lights on for a couple of days (thats how i know how my bike behaves when the batterie is dead)....if its a spark related problem and not fuel. maybee you damaged a bit of the wiring so its not making a good connection or have bent or something the rotor behind that black suzuki cover that came off when the bike was dropped (3 bolts holds that cover on), you could pull it off and look for a frayed or broken wire, and trace it back up the bike a bit to make sure its not broken elsewhere

i'll have to check that out too, what IS behind that cover?

That's where the ignition components are. A couple wires, a sensor, etc are on the end of the crank.

Did you happen to change spark plugs post crash?
If so put the old ones back in and try it.
Cool.
Buddha.

Nope, they're the same. But I prob will change them once I sort this out, that plug on the bad cyl looks pretty bad..

detonation is a common issue in 2 strokes and can cause similar issues to what you describe regarding the cracked header, although I don't think it's that common in 4 strokes....just a thought.  The cracked header is the cause of your backfiring for sure.....cold outside air mixing with hot ex gasses before the endpipe will definitely cause backfiring.  Bad/old gas will sometimes cause blowback from the carbs back into the airbox......is your airbox full of gas?

-Craig

Didn't get a chance to even look at the GS yesterday, hopefully today though.

The crack isn't in the header, its actualy on the very end of the muffler can right next to the outlet - I'll have to take a picture, it kinda impressive - although the muffler looks like its already been fixed once before. Its AL.

The airbox seemed pretty dry. Although it had some pellets in it that looked like rate poison, I'm sure it would be pretty hard to do, but it would suck if one of those bounced up and got sucked into the engine!

Right side drop? After you assure yourself it's not in the carbs (that they are clean and manifolds are tight to the block) I'd double check your ignition system for damage. Something loose that's moving around and causing intermittent issues.

I didn't do much, but I pulled the case cover. The wires/pickups looked fine, I just managed to pick up  a few pebbles in there.

Here's a pic of the crack:


I rode it a bit, seems to run well while choked and cold, as it warms up it gets worse until it won't idle with out constant throttle. Or with out the choke.

Hopefully I'll get to check more this afternoon...

So the ignition side had rocks and trash in it after the low side? And it's been in there until just now? 

I assume that you've replaced this cover now. If not, Buddha sells a nice thick replacement cover. The OEM cover is garbage, IMHO.

I'd check the ignition side carefully. You're looking for either loose / broken wires or pickups. I'd actually remove the ignition components from the bike and visually inspect them for obvious damage (cracks and such).

The sudden onset of your problem, plus the backfiring, makes me think you have an ignition issue, not a carb issue. Carbs tend to just get worse over time, but I've never had one just go "bad" on me while riding.

There were two pebbles sitting in the bottom and a little bit of sand/dirt. I checked them pretty well, but I'll look again.

I did ride  for a good 20 hrs post crash before noticing any issues though. And the conditions did get worse over the last 3 hrs of riding but I see what you're saying. I wonder why it would vary with engine temp though...