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Discussion Starter #1
Picked up this bike a month or so ago. Had trouble starting it and keeping the battery charged at first. Got a new battery and replaced the alternator rotor and that seemed to do the trick. Different problem now, though. It starts up ok but after getting warmed up, the bike seems to lose power or not being firing on all cylinders. Doesn't seem to matter what gear or what speed, it'll just lose power and shut off. Could be something to do with the regulator or the fuel filter? Any input appreciated.
 

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Troublemaker
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Could be the petcock is not allowing enough fuel to the carbs, could be gummed up. The symptoms sound like it is slowly starving for fuel. Once it sits, the carbs fill back up and it will run for a while until it runs out of fuel again. Could also be a fuel filter, if I remember right, there are screens on them, and they eventually just deteriorate and clog things up.
 

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Seconding the fuel line problem. Always replace the lines when you buy a bike since chances are they haven't been touched since manufacturing. There could be clogs or the line could be deteriorating.

How long does it take to die? Does it sputter and die? Can you rev it before it dies?
 

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Discussion Starter #4
I just took it out and after awhile it sputtered and died. I checked the fuel filter and it looked almost completely empty. Shouldn't it normally be full? What's involved in cleaning out the petcock?
 

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Fuel filter should never be empty...

Run it till it dies, if the fuel filter is empty, then it is either plugged or the flow to the filter is restricted.

Shut the valve off and pull the hose off the input to the fuel filter, Put the hose in a cup and open the valve, gas should flow easily...if not, there's a restriction..you can try blowing air back through the line (air hose, not with your lips lol) and see if that opens it up.

If the flow is good before the filter, then hook the filter back up and pull the line off the filter exit and see if fuel flows well through the filter.

I had a 550 and battery charging was ALWAYS an issue with that thing...below 1800 RPM and the battery was in a discharge state.
 

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Discussion Starter #7
Ok I replaced the fuel line from the petcock to the carburetors and put in a different, smaller filter. It seemed to be ok. I rode it about a mile to the gas station to fill up. After filling up it wouldnt start. Also, gas was dripping out of the (carburetor overflow?) line under the body at a decent rate. Why/when does gas flow out of that line? It took the carburetors out and to try and find anything, with my limited knowledge. They looked pretty clean and in working order as far as I could tell, the floats werent stuck or anything. Put everything back together and started it up, rode it around for 10 mins, everything seemed fine. Didnt seem to be any leaks. Go to look at it this morning and plenty of gas had leaked out of the overflow tube overnight. Any thoughts? I would just take it to a repair shop but it took them about a month to get it back to me and I still had issues with it.
 

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Gas out of the overflow hole is most likely a stuck/defective float. There is a float inside the carb...when the gas is low, the float allows fuel in, as gas comes in, the float rises to a point where it shuts off the flow. When that mech doesn't work properly, 3 things can happen:

1. Stuck up, bike will not start as there's no gas in the carb.
2. Stuck down, gas will pour out the overflow tube and into cylinders.
3. Intermittent stuck up/down...drives you nuts with dying and gas coming out the overflow plus wet plugs.

Some bikes have a spring/vacuum mechanism inside the petcock. If you have a hose from the petcock to the carb, then your bike has that mech and gas should not flow with the engine off. Be sure that vacuum hose in there and in good shape. If it is, and gas still flows with the engine off, then it's defective, easiest fix is to just add an inline fuel switch; that way you're in total control of when gas should flow.

Search YouTube for this video; guy does a great job of explaining your carb:

How Motorcycle Carburetors work and how to tune and clean them
 
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