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Headlamp Lens Melted

9K views 30 replies 13 participants last post by  STroadster 
#1 ·
The Street Twin has just suffered its first real fault. While giving it a clean I noticed that the headlamp lens has deformed and melted and has a crazed area on the inside. Just about to take it for first service so I'll see if it can be replaced under warranty.
 
#2 ·
I was afraid of this.

First, did you replace the original H4 head lamp with one of larger wattage, and thus greater heat? Assuming you didn't:

Under Euro 4 Triumph was compelled to go from glass lenses to plastic ones, probably acrylic. Glass lasts forever, but breaks into sharp shards. Acrylic doesn't shatter into slivers, but it can be melted. In time it is subject to cracking, fogging, and crazing.

The headlamp on water cooled twins is nestled right into the middle of a large metal heat sink. This design is used in an effort to absorb, distribute and dissipate excess heat, sparing the plastic lens and shell. Sounds like this arrangement didn't quite work.

This design didn't really look sufficient on my T120, so I installed the following to keep the headlight turned off after the ignition is turned on until I'm ready to ride away. Then, there's plenty of cooling airflow over and around the lens and bucket:

https://newbonneville.com/shop/easy-start-headlight-control-module/

It works great. You only have to remember to toggle the headlight on, otherwise you're riding with just that dim parking lamp.
 
#14 ·
I'm glad they used plastic. Already have a decent rock chip in mine that probably would have shattered a glass lens. Lights work very well IMO. The low beam does have a small dark spot where the light is apparently blocked by that lovely little "T" badge. Not really any big impediment to the night view though. I thought the brights seem to light up the corners fairly well too.
 
#4 ·
Just to confirm I have not changed the bulb and the Street Twin does not have the daytime running light option. I wonder if the situation is made worse by the Triumph touring screen. It might reduce the air flow through/over the headlamp. But of course if you are stuck in low speed traffic that wouldn't make much difference. I can't see an easy fix for this unless the headlamp design is changed to increase the distance from bulb to lens or the material is changed to be more heat resistant or have greater thermal conductivity.
 
#5 ·
Just to confirm I have not changed the bulb and the Street Twin does not have the daytime running light option.
Not sure I follow here...so you being in the UK, ride with the bright (high voltage) LED DRL on unless you toggle the headlight switch and actually turn on the headlight to its low beam. When done, I think the LED DRL (?) and the low beam are on at the same time? So, do you ride with the low headlight beam on or with the LED DRL on?

In the U.S. we are required to ride with the low headlight beam on and a very low voltage LED is on, as our daytime running light. Some have already changed over to operating the headlight the way you are able to - but that is not an inexpensive thing to do - it requires the EU left hand switch and a new EU headlight with the higher voltage LED DRL built in. tsmgguy (a U.S. rider) is using a different method with an optional (aftermarket) wiring harness that keeps the headlight low beam off when starting the bike, but apparently allows the low voltage LED to operate once the ignition is turned on. Then in order to turn the low beam headlight on, thje U.S. high/low beam switch is toggled once, toggling a second time activates the high beam headlight. I think I have this correct...tsmgguy comments?

Strangely enough, my low beam bulb just burned out on my T120, leaving only our low voltage LED on as a DRL and when I toggle my headlight switch, I go to my high beam headlight, the bike believing that my low beam headlight is already on. It is rather unusual to burn out a headlight bulb this early in their live as these bulbs generally live a long life...so I wonder if my headlight might be experiencing perhaps some heat issue too? The plastic lens nor the reflector on my headlight is not deformed or discolored in any way though...
 
#8 ·
Can't imagine that the Triumph touring screen would be the cause of enough cooling airflow disruption to cause the headlight lens to melt.

I always ride with my T120's high beam on during the daylight hours. On the next ride I'm going to stop and lay hands on the headlight bucket and lens assembly to see just how hot they're getting.

You'd think that there would be a way to replace the plastic headlight assembly with steel and glass on an after market basis. The problem is that Triumph's lenses and headlight shells are not of standard sizes. Also, Triumph has taken advantage of every nook and cranny on these bikes to hide wiring and electrical components. The upper portion of the headlight bucket on my T120 is just chock full of wires and connectors, with a large hole in the back, probably placed there as much for cooling as for the routing of all that wiring.
 
#28 ·
What has been the answer to your original posted issue by the Triumph dealer? I'm not sure that I've seen a response to why that has happened to your bike in the previous 27 postings...anything further? I too doubt that running with a windshield could/should cause something like you've experienced.
 
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