550 ran awesome yesterday, today, won't start. any ideas?

[chuckycheese]

Yeah

Here today and gone tomorrow is usually electrical. Points, coils or connections.

Yeah....I'm constantly amazed at how quickly things can turn to sh*t on these bikes!

[Nessism]

Yeah....I'm constantly amazed at how quickly things can turn to sh*t on these bikes!

Things turn to sh*t because most people don't do maintenance.

What amazes me is when people buy and old bike and then scratch their head when it doesn't run right. What are these people thinking?

These GS bikes are OLD - 30 years old in some cases. The carburetor o-rings are hard and dried out, the valves need to be adjusted (many GS bikes have never had a valve adjustment), the brake system is full of sludge (which can NOT be flushed out by just changing the fluid), wiring harness has corrosion and needs to be cleaned, etc.

Do the basic maintenance when you first get the bike and it will be reliable. Do the bare minimum and the bike will continue to break down all the time. Pretty simple.

[Sick Steve]

Eh...Hate to burst your bubble on your carb/spark quest, but when's the last time you adjusted the valves? If its been as long as its been since you tore the carbs apart, you are WAY WAY past the adjustment interval, and THIS ALONE would cause all of the symptoms you describe. As these motors get older, the valves receed INTO the head, making the clearance TIGHTER, thus, eventually the valves will NOT close all the way. Lean conditions then result, and no amount of fiddling with carbs or spark will correct it. In fact, the more you mess with the carbs, the worse off you're going to be when you get the valves adjusted, because now the air/fuel ratio will be completely different. This is NOT an optional maintanence issue if you want the bike to run. If you continue to run the bike without adjusting the valves, eventually, it wont start at all, and worse your're going to burn all of your valves and torch your pistons/rings/cylinder walls. The valves should at LEAST be checked every 3000 miles, and maybe or maybe not they would need a couple shims changed out. The tollerance for clearance is .03-.08 mm. Thats not alot of headroom. I suggest that you check into the clearances before you do anything more with your spark or carbs.

that figures.... how does one do this?

[chuckycheese]

That too

Things turn to sh*t because most people don't do maintenance.

Well, that too, but things just plain go wrong with these old bikes. Old people can take very good care of themselves....but they still, inevitably, develop health problems. The concept is pretty simple and undeniable. You've just gotta do the best you can!

[brand new bike zealot]

almost 2 month follow up

Just thought I'd give the answer (so far) to my engine issues. Turns out that the plugs were very fouled, combined with spent points and condensors. After fresh plugs, new points and condensors, she's back to running like an absolute dream, well as absolute as can be expected for a 30 year old machine..... Had the carbs synched at the same time, but they really weren't too far out so I don't think it had much to do with the original problem.

It's been 1000k since the fix, and when I pull the plugs, they are light brownish, about right as far as I can tell. Yippee!

I also got a new to me back tire put on, so I feel a little more confident on anything other than jet black blacktop on a sunny day!!

Back in love with my GS!