Any idea what is causing these motorbike problems?

1. Loss of power
***Problem:
———-Bike loses power and begins to pull and jerk sporadically. On occasion the bike dies altogether. It feels as though the bike is lugging, only half the cylinders are firing.
***Symptoms:
———-Usually occurs when the bike is warm
———-Usually occurs at speeds above 110km/h
———-Sometimes happens during intense acceleration
***Remedy:
———-Riding at slower speeds (below 110km/h) seems to avoid the problem.
***My best guess:
———-Water in the carburetors
———-Water in my gas tank
———-Spark plugs /gap

2. Front tire shake/wobble
***Problem:
———-Front tire/forks shake violently
***Symptoms:
———-Front tire shakes most violently when decelerating from 80-70km/h
***Remedy:
———-No “Look! No Hands!” between 70-80km/h!
***My best guess:
———-Tire balance
———-Uneven wear

3. Front brake shake/wobble/pulse
***Problem:
———-Front brake pulses/surges when applied
***Symptoms:
———-Most noticeable at slower speeds with gradual braking
***Remedy:
———-None
***My best guess:
———-Related to tire balance
———-Uneven disc
———-Wheel alignment

4. Backfire – during deceleration and starting
***Problem:
———-Extremely powerful/loud backfires often on startup and always when decelerating on the highway.
***Symptoms:
———-Usually happens when decorating from 4th to 3rd and 3rd to 2nd (90-40km) range on the highway. Little burps, hiccups and big bangs.
***Remedy:
———-Working the clutch on deceleration – clutch in, clutch out, clutch in…
***My best guess:
———-Water in my carbs
———-Timing

5. Decreased gas mileage
***Problem:
———-Bike gets very low milage, an average of 14km per liter
***Symptoms:
———-Have tracked my milage for a year and it has decreased from close to 17km per liter in October 2007 to 14km per liter in September 2008.
———-According to other Hyosung GT 650R riders mileage should be closer to 19
***Remedy:
———-None
***My best guess:
———-Carbs
———-Timing

I know this next section is lengthy, but I think it has some key information.

Bike History:

I purchased my used Hyosung 650 privately about a year ago, it had less than a 1000km on it. It was on sale because the guys son had managed crash it after only a few weeks. I was concerned about buying a crashed bike so I test drove it extensively looking and feeling for anything that was out of alignment. I did have a few backfires during the ride but I attributed them to a bike that had been sitting for a while and a near empty fuel tank (I actually ran out of fuel on the test drive).

After purchasing the bike I rode it over 300km back to my town. During this ride I noticed the bike became harder to start as it got warmer. When the bike was cold it was never a problem, but after 40+ minutes of riding the starter really struggled to turn over and failed altogether at times. The problem got progressively worse with time. Near the end of the ride I started losing engine power, the bike would surge and stutter, go – stop – go – stop – go – stop until the engine cut out and I rolled to a stop. I had to wait for the bike to cool before it would start again (even push starting wouldn’t work) and then I could ride her until she warmed up. Shortly into the ride the power problems would start again. I found slowing down to about 20km/h, applying some choke, revving the engine and working clutch just barely allowed me to get into the next town where I was forced to park for the night.

Being a Canadian in Korea, I can’t communicate well with the mechanics here and while they are cheap, most are neither methodical nor proficient at isolating problems. After a few tries they managed to fix my problem. They changed out the battery, starter and, I believe, the regulator (a small electronic component, housed in a black plastic box, found under the seat towards the left side, it’s screwed into the frame and some wires clip into it). After this my bike was good to go, until last month that is.

Last month the mechanic insisted my starter was the problem while I tried to convince him, in broken Korean, that there was something else at play. My starter had again become weak at high temperatures, gotten progressively worse and then died altogether. This time however, my mechanic didn’t change the ‘regulator’ (little black box). The bike has been starting well for the past month but even now I think I’m noticing signs that starter is beginning to go, it’s still a little too soon to tell for sure. The loss of power problem appeared during this last month and just when I thought I had managed to associate the problem to speeds greater than 120km/h I somehow was able to cruise down to the bike shop yesterday at prolonged speeds between 140 an
and 160 with no problems. So now I’m a little confused, perhaps water isn’t the problem.

I wanna fix this problem for good and go out on a three day tour at the end of the month. I’ve included a list of all my current bike problems below, any information you may have would be really appreciated.

Thanks is advance for your help,
-Greg

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