Sportster runs fine for a few miles maybe 100 miles,but then fouls plugs and will not stay running. The only thing I've changed on the bike is I put slip on pipes on it.What do I need to do to fix this problem? It is not a fuel injected model.

 

Are the plugs wet or dry?

 

Plugs are dry

 

Dry fouling usually means you're running rich. Do you notice black smoke coming out of the exhaust?

 

A couple of questions-

When did the bike start doing this? What year is it? How many miles(does it only have 700, or is that what you've put on it since you got it)? Did you recently change anything (jetting, air filter, spark plugcaps or wires, spark plugs)? How old is the gas?

Some obvious stuff-

Is the air filter clean and unobstructed?
Is the choke (enrichner) off?
Do you have the recomended plugs installed?