Mysterious Problem

[ColinClayton]

I have an 83 550L that was running great, when it ran into a charging problem. I narrowed it down to a bad stator, and considering rewinding it myself, but ended up finding a good deal online. The bike sat about a month, and after swapping the stator it won't start. I have a good spark on all four plugs, compression of around 125 on each cylinder, a new air filter, no vacuum leaks, and fresh gas in the tank. I thought it was a fuel problem but after soaking the carbs and cleaning them thoroughly, there was no luck. If anyone can think of a solution, it would be much appreciated.

 

[loud et]

Maybe the carbs aren't primed yet...aka bowls not filled. Faulty petcock, prime function not working.

 

[ColinClayton]

There is a clear inline fuel filter where I can see gas entering the carbs, but I drained the float bowls to double check.
If the starter clutch pin or washers were installed incorrectly, could they cause this problem?

 

[tom203]

?..
If the starter clutch pin or washers were installed incorrectly, could they cause this problem?

If it cranks over, this is not the problem. Crank a bit with choke "on " and see if spark plugs are slightly wet - to make sure you have some fuel.
Double check spark plug wires on correct plugs: left ignition coil (as you sit on bike) fires 1 and 4- easy to mix up!

 

[TxGSrider]

Have you tried starting fluid?

 

[Steve]

Have you tried starting fluid?

Please don't suggest starting fluid. It is just a Band-Aid that is far too easy to mis-use, causing a LOT of damage.

ColinClayton, when is the last time you checked the valve clearance? I'm not saying that is the problem, but tight valves make an engine harder to start when cold.

Also, your inline filter might cause some problems, too. Not so much when trying to start it, but some of them are rather restrictive, since they are designed for cars with pressurized fuel systems. Our gravity-fed fuel systems simply don't have enough pressure to push fuel through in quantities sufficient for sustained high-speed running. Your smaller engine might get away with it, but your fuel is already filtered twice before it gets into the float bowl, why do you feel you need a third filter?

.

 

[TxGSrider]

Please don't suggest starting fluid. It is just a Band-Aid that is far too easy to mis-use, causing a LOT of damage.

ColinClayton, when is the last time you checked the valve clearance? I'm not saying that is the problem, but tight valves make an engine harder to start when cold.

Also, your inline filter might cause some problems, too. Not so much when trying to start it, but some of them are rather restrictive, since they are designed for cars with pressurized fuel systems. Our gravity-fed fuel systems simply don't have enough pressure to push fuel through in quantities sufficient for sustained high-speed running. Your smaller engine might get away with it, but your fuel is already filtered twice before it gets into the float bowl, why do you feel you need a third filter?

.

Actually, if used properly, it can be a great diagnostic tool.
Shut off the fuel, and use the fluid. If it runs for a few seconds on starting fluid and sounds ok, you can lean towards the idea that its not drawing mixture into the cylinders and the ignition system is at least capable of igniting the charge. So then you can check for carburation problems or air leaks. If it doesn't start with the fluid, then it may be a an ignition problem (weak spark).

 

[tkent02]

Actually, if used properly, it can be a great diagnostic tool.
Shut off the fuel, and use the fluid. If it runs for a few seconds on starting fluid and sounds ok, you can lean towards the idea that its not drawing mixture into the cylinders and the ignition system is at least capable of igniting the charge. So then you can check for carburation problems or air leaks. If it doesn't start with the fluid, then it may be a an ignition problem (weak spark).

There are far better ways to diagnose an ignition problem.

 

[ColinClayton]

I think it ended up being switched ignition coils as was suggested.
Although it still would not start initially and had to use some starter fluid, it now starts on its own.
I had recently adjusted the valves to specs before I had garaged it for a month.
Thank you!