I replaced my stock sealbeam 35/55W with a 55/100W H4 on my old FXSTC.
No problems running the hotter bulb.

It does look like corrosion on the contact. Once connected, dielectric grease over the exposed connectors should keep it from happening again.
I'd also look at sealing the head light shell.

 

I agree, but I would suggest you first make sure the connector fits tightly and put some dielectric grease on before you push the connectors together.
Put another thin layer over any bare metal after its connnected.
That way it keeps water out and helps conduct heat better.

 

Another vote for a corroded connection at the wire and the terminal. Corrosion is "expansive" which means it takes up more room than the metal that is actually corroding. This loosens the crimp and spot weld junction that is used in the O.E. harness. The effective decrease in wire size as the corrosion essentially pry's the crimp open, generates a lot of heat, even with the current draw of a stock Headlamp.

 

Thanks for all the info. I've been running a factory bulb same watts. I found my factory headlight with the harness that looks to be better quality. I'm going to splice and dice that plug in this week and I'll be sure to add some dielectric grease.
Thanks again!

 

If your going to splice the plug into the existing lines DO NOT USE cheap butt or crimp connectors.
They might work fine for a lot of different things, but they will NOT work for long on a bike.
The best way to connect two wires on your bike is to solder them together and waterproof the connection.
If you don't know how to do it right, and anyone else who might be interested.
Here's a link to a post I put up in the DIY section to show you how to do it so it will not give you problems later on.

https://www.hdforums.com/forum/softa...ml#post3307100

Good luck and ride safe.