jeffja

When you ask if there is spark and mention the coil, that brings up an interesting thought.

So in my original post, I mentioned that SOMETIMES only one cylinder would fire when cracking the throttle or holding a short rev. One question is... could that single firing be caused by the possible fueling issue, does that sound purely electrical, or otherwise? Also, can a coil begin to go bad and work sometimes, or is it a black and white thing where it either works or it doesn't?

 

How do you know that it's only firing on one cylinder?

 

The answer to your question is yes. It's not a broken/not broken thing all the time. You should be able to take the coil to a dealership or possibly an auto store (oreilly or something; not sure on them though) and have the coil tested. Electrical is more of a painstaking, methodical isolation procedure. I like to do the easy first. Eliminate all the simple things, fuel filters, fuel lines, petcock/pump, bad grounds, loose battery connections, etc. If none of that turns results, then it's more indepth i.e. taking apart the carb for inspection, testing voltage regulator, tracing wires..etc

 

Ok, I'm back... so it would run on one cylinder while holding a mild rev... instead of the engine making the steady one-two engine noise... it'd be one-two, one-two, one, one, one, one, one-two, one-two...

I took the air cleaner off, removed the fuel line from the carb, then took the gas tank off... Dismantled the petcock. No clogs. Checked the vaccuum line from the petcock to the carb and it also seems ok. Emptied gas and put new gas in.

One thing I did notice was that there is a port under the other side of the gas tank with a rubber line coming off of it. Tried looking this up and coouldn't find anything that helped out. The rubber line runs back between the engine and the rear wheel, points downward toward the bottom of the bike and is not connected to anything...

What is this line, what does it do, and is it supposed to be connected to something down there??

 

I believe that rubber tube would be the fuel tank vent. It's connected to the small metal tube that you see when you take your fuel cap off and look into the tank, just above the hole where you insert the gas filler nozzle when you fuel up.

=8^)

 

That is probably the tank overflow vent line. If you overfill your tank gas will spill out that line.

 

It doesn't get connected to anything. It's a gas tank filler neck overflow tube. Remove the gas cap and you'll see another metal tube sticking up from where you put the gas pump handle.

 

Guessing at bad fuel, from the bike sitting less than a year, is just wishful thinking.

Either buy the service, diagnostics and parts manuals or take it to a pro.

 

Have you swapped plugs? Maybe a bad spark plug.

How about swapping plug wires. Maybe you have a damaged wire that produces a weak spark. Have you checked for vacuum leaks on the cylinder that mis-fires?

Opening up the carb is pretty easy, just follow the posts on carb rebuild. You can check the stickies on xlforum.net for detailed information.

John

 

Thanks for the info on the gas tank vent and overflow line information.

I did replace the wires and plugs for new before all this happened. I saved the old and will put those back on to see what happens. I will also try to go get my coilpack unit checked to see if that's good.

Thanks for the vaccuum and carb info John. I'll look into that too.

Process of elimination. The more I play with it instead of taking it to the shop makes me more comfortable with it. I like that... but there may be a point where I just cannot do anything else and would have to take it in. I'll try a few more things and post again later this evening.