need help with my GS.....

[Jarrod]

I was riding my 1977 GS 750 to work the other moring....
about 6 miles into my trip the bike started running really
ruff in the upper RPM range...it would idle at a stop but kinda
ruff...about 45 mph would all it go....it was popping and back firing some..
my bike only has 11,700 miles on it....
factory stock also...
it is getting fuel..any ideas anyone? I plan on tearing into it
tommorow and checking it out....

thanks for all the help

[mark]

Pull the plugs and tell us what color they are.
Make sure that you've got spark at all four plugs. You might have lost spark to a cylinder or two. Check your plug wires and plug caps for good connections. You can feel your exhaust at start up. All four pipes should warm up evenly.
Check your timing and point gap. Points shouldn't be too pitted and close evenly.
How's your battery? Should be fully charged. Check connections.
You're vacuum hose from the petcock could be drawing fuel and flooding your engine.
Air cleaner O.K.?
Air box sealed good?

[Jethro]

9 outta 10 times, a rough running condition that comes on suddenly is electric related. Check the charging system, coils, battery, everything.

[duaneage]

Fuel delivery problem. Check for bad petcock diaphram, dirty fuel filter, kinked fuel line, dirty screen in the petcock.

The loss of power coupled with backfiring might indicate a lack of fuel.

[gremlin]

clean out the carbs. check the air filter. i bet it has a hole in it or came disloged. one ay or a nother you have got some crud in the carb. i have had this happen a few times.

befor i sold by bike. the thought of making a brand new tank sealing it with a plastic liner and a new manule fuel tap. all just so i could seal it tight and have a filtered tank vent. lots of dust entering the tank would couse me to flush out carbs and tank twice a year.

[flyingace]

It can be either electrical or fuel. The first advice was best. Look at your plugs. If they are misfiring, they'll be wet, sooty, fouled. If it's fuel starvation, they'll be dryer and closer to normal appearance. An over-rich fuel condition could lead to sooty plugs, but my experience has been you notice that more at idle speeds.