as of friday I have owned my XT660 R for 12 months now and covered nearly 11,000 miles, in that time I have had to replace the headlamp bulb 5 times although 1 of these was due to water getting into the headlamp
I mainly use my XT to commute on A roads so pretty much flat out all the way
so is a headlamp bulb failure common every 3 months or so? is it the vibes from constant top speed running? am I just buying the wrong bulb (Halfords super bright H4 at about �15 a go)? is there a heavy duty bulb that could cope with the use i give the XT? as you probably know bulb swaps aren't something that can easily be done at the roadside so i would like a fit it and forget it option

I've had some trouble recently on one of my bikes (not the XT) with blown bulb. Mine was down to a faulty regulator causing volt spikes which eventually also killed the newish battery.
It might be worth just double checking all the plugs and connectors for loose connections etc. A loose connection might cause the light to flicker and die.

bulbs look like they have been shaken to bits rather than blown by voltage i.e. they are not blackened

I read a used bike test of XTR 660 & F650GS a while ago(2008).
There was a mention of some XT's being bulb blowers but there was no explanation for it.
What year is your bike. Have you asked Yamaha dealer or technical support?
Philips do heady duty bulbs which are vibration resistant as well as one called motovision.
As already mentioned, high constant voltage or spike will reduce the bulb light. A blown bulb is not necessarily blackened: you will see a broken filament.
I changed the bulb in my 2009 XT at 1000 miles because of brightness during winter months with Halford 50%+ (which is actually GE). It is still fine

I had this problem too, three blowing in as many months. Not had it again since (touches wood). I made sure the headlight unit was securly sat on the rubber cushions in order to minimise vibes...might be something else though?!

http://www.xt660.com/showthread.php?t=9074

__________________

what the others say,plus i packed some old innertube around to damped vibs on front and rear lights .Worth checking electrics out if you keep havin problems

Arrgghh!!! I had to open my big mouth!! Yep, you guessed it...blown headlight while riding today lol

at least the days are long for a little while longer

__________________

put some neoprene behind bulb holder as bulb was very loose when fitted, new bulb is OK (for now) doing 250 miles a week (done nearly another 1K miles since new bulb fitted) mostly on very vibey concrete A road at full speed

Used only name brand bulbs.
Do not touch the glass, the grease & oils from your skin will make the bulb pop sooner.
Vibration kills these bulbs, inspect the head lamp & cowling for any loose bolts.
Make sure the clutch cable is routed correctly & not touching the back of the head light or bulb holder.
Check the voltage at the bulb at 3500 rpm.
Check the earth wire at the bulb with the bike running with a multimeter, + lead on the earth wire at the bulb holder, - lead on the negative lead on the battery, what is the voltage reading? should not be more than 0.02 Volts.

__________________
Click here to join the XT Supporter's scheme

Mods that I have done to my XTX's

My 04 XTX
Stage 1 & 2 DNA filters / Kev fuel mod / snorkel mod / Drilled air box mod / Engine breather mod / Fork Spacer mod / 15w fork oil /
[
My 07 XTX
Raptor 700 cylinder 102mm / Modified Crank Case to take a 105mm Raptor Cylinder / 11:1 102mm JE Raptor piston / Stage 1 Raptor Hot Cam / Ported head / Colder Spark Plug / +2mm Throttle body / DNA stage 1 & 2 filters / Modified Air Box / Snorkel removed / Worry Brothers stage 2 filter cover / 6mm & 8mm Bolts Replaced with Titanium Bolts / Recovered seat in Black / O2 Eliminator /

My 09 XTX
59HP at the rear wheel / Stage 2 Raptor Hot Cam / DNA stage 3 Air Box / Carbon Can Exhausts / Modified Exhaust Link Pipes / PCIII With Custom Fuel Map / Wideband Commander O2 Data logger / LCD100 Dyno Jet display & fuel adjuster / 2500 OHM HT lead instead of a 10K OHM XT lead / Extra Coolant Cooler / Protaper Fat Bars / Tail Tidy With LED Tail Light / OKE Protection Knobs / LED indicators / AIS blocked / Modified rear sprocket rubbers / Rear Foot Pegs removed / 09 ECU With 02 Sensor Changed To A 06 ECU / Complete wiring harnes Changed from 09 to 04 / Home made LED resistor flasher / Hole drilled in the fuel tank filler neck to allow quicker filling / Modified Bar End Weights / Progressive front fork springs, 15W fork oil, forks lowered 25mm, used XTR rear links lowering the rear 20mm, rear spring one click stiffer / Changed front & rear guards from blue to black / 47T rear sprocket / Speedo Healer V4.0 / Kev throttle cam mod / Throttle grip mod / The new 2010 O2 sensor mod is out, works a treat, The new 2012 O2 Controller is out, PM me for details

Now ride a 2018 MT09SP ABS + TCS

My KTM 990 SMR Mod book. http://www.ktmsmt.com/viewtopic.php?f=13&t=4946