I here a bang and she stalls

[Anonymous]

When my 400 is idling while warming up I sometimes get a bang from the left hand cylinder area and she stalls(doesn't even spin down, it stops dead). After this I just start her up again and generally don't have this problem for a few days.

This problem has been developing as it's been getting colder. Today the bike had 2 inches of snow on her when she did it. Another worthwhile note to make is that it looks like I have a carb fuel leak from the left hand side when I park and put it on the side stand(again, only once in a while). Maybe it's actually a hydraulic lock? Perhaps its just a backfire? I'm not too sure...it almost sounds like mechanical contact but it can't be since the bike continues to work.

I'm hoping that when I put Robert Barrs o-rings in this weekend it will clear up but I need to know where to look in the carbs since they must be the problem.


Thanks, Steve

[SqDancerLynn1]

Cold weather problem?? Check that the coil/plug assembly is clean no cracks in the plug wire, check the plug caps. If it is dirty it could be shorting out due to moisture. Fix that fuel leak!

[argonsagas]

Perhaps you need to refer to Billy Ricks.

Detonation causes a very large amount of stress on internal parts when it stops the engine.

It could be carbs, but since the engine is already running when it occurs, my first suggestion is to check for cross-firing due to moisture/frost.

Look at your plug leads for cross-fire. It's easier to see after dark. You may have damaged leads.

Bad wires should be replaced, but a temporary measure is to put split-loom over them. It increases the space between the leads and other metal parts, thus decreasing the arcing. Silicone glue may also help seal any cracks...never tried it, but it sounds logical.
0-rings may be what you need for the leak. Be sure to thoroughly clean the carbs while they are open. If you don't have a fuel filter, put one on.

If the fuel leak is substantial, you need to check the petcock as well. I think yours has the vacuum-type, but I'm not certain. If so, you just pull off the fuel line at the tank and see if it leaks. Do not leave it set on Prime.

[daveo]

I had a starter clutch go bad and do stuff like that, a big Bang and a shudder,

[Anonymous]

It appears to be an issue with the choke. If I am using a bit too much choke the problem occurs. I was going to rebuild the carbs tonight but I can't find a pail of carb cleaner.

Oh yeah, I can put water in the carb cleaner right? At school we did this as the water would float on top of the cleaner thus preventing evaporation (and smell).

Steve