New to HDforums so hello to all. I have a 99 Electra glide. 95" big bore kit,570 gear driven cams. My question is when I mash the throttle at low speeds and the motor is under load it sounds like there is a rattle in the front exhaust pipe. What do you experts think? At first I thought a loose bracket but I cant find anything loose.

 

Sounds like your engine is pinging/knocking. You described what causes most pre-detonation, pinging, the low engine speed,engine under load, and applying lots of throttle. May I suggest that you down shift when you do this. A lot of "new" harley riders like to drive slow in a gear to high and this causes the engine to lug. Welcome to the forum.

 

This rattling is while I am in 5th gear running 55 mph and open the throttle up. One of my friends said it was detonation. I am wondering what the countermeasure is to this. A tune up?

 

55 in fifth?

 

You need to google these terms to learn what's happening. A tuneup might help some of it, and allowing the engine to run at higher rpm so it's not "lugging" will help too. Outside air temperature and engine temp also factor in to when it might ping, etc.

 

Higher octane fuel will help;Grab lower gear instead of lugging motor.