I have a 1978 Sportster that will almost start. It fires exhaust out the back for a second or two, but then it immediately cuts out. It doesn't want to run for more than a second or two. Anyone know what the problem could be? I just got a new ignition coil and spark plugs.

 

You might wanna provide a few more details for those in the know. How long since it was running? Fluids new or not: sitting or drained before. Stuff like that.

 

First off do you have plenty of fuel in the tank? Second, has the bike sit for a long time? If so you may have some jets clogged up and have to clean out the carb. Give us a little more info if you can.

John TN

 

It was running a few days before. The ignition coil and spark plugs are new. It has plenty of fuel. It has an SS carb on it. I believe that that is very new.

 

Have you done any adjustments to the carb? Also did you replace the coil and and plugs after it had been running a few days ago or were they on it then.?

 

I'm thinking your timing may be off. Try small adjustments in one direction to see if it gets better or worse. Take if from there. What series carb does the bike have?

 

Also adjust your pushrods. Your bike has solid lifters and they need attention every couple thousand miles or so.

After it tries to start and quits, do you still have spark?

 

It ran well after the ignition coil and plugs were replaced.

 

I took it to a mechanic when it didn't start and he replaced the ignition coil and plugs. It ran for a week. Now i have the problem listed above.

 

Ok, go back to the basics. Maybe a wire has come loose or disconnected from the coil install, pull the plugs and see if you're getting any fire, you could have fouled a plug, and just because a plug fires out of the cylinder it still may be fouled and not fire under compression.

Do a compression test, both cylinders should be within 5-10 pounds of each other and I'm not sure what the compression should be for the sporty, I'd guess at least 150 lbs but thats a guess.

Pull the fuel line off the carb and make sure you're getting fuel to the carb, if you have fuel, compression and fire it should run. If the compression is good, and you have spark and fuel to the carb and it still won't run then you might have trash or water in the carb.

Let us know what you come up with.

John TN