Got a really good torch off ebay a while back but when I go over a big bump it either goes off or goes through its cycles.
It's not as bad on my suspension forks as my rigids.
As a torch it's perfect but not so good on a bike.
Any ideas?
Strap it to your helmet..
Can you replicate off bike?
[quote=zippykona ]Got a [b]really good[/b] torch off ebay a while back
Or maybe not?
Sounds like it's faulty so go for the warranty option.
It's too big for a helmet torch and if I shake it really hard it it will go through the cycles.
As I said above its a great torch not a bike light.
Saying it's the cap. If you take it off is there a solid copper pill not a spring?
My Trustfire torch did that, and stopped working altogether later. So, er, no ideas, sorry. Have since had another which works OK.
There's nothing quite like threading through trees on a downhill steep enough that you don't dare move your hands off the bars, with your head torch in flashing "disco" mode!
Is it a battery pack or does it take a 18650 battery?
If its the one just bigger than a AA then either try using a quality battery with the extra power surge at the end (only comes on the more expensive ones)
Does it only cut out once the torch has been on for a while and not when its first used and fully charged?
Or wrap Some tape round the middle to stop it rattling. It could be caused by the battery moving and losing connection.
The clicky-clicky torches change modes by interrupting the current - so if the cell is not snug and you hit a bump (or shake it) the torch will change modes. It should not turn off though.
If you wrap your cells in electrical tape they will move less (you can also use a small strip of plastic cut to jam the cell in more tightly). Another fix is to make the cells longer using a small rare-earth magnet or even a small screw in the tailcap spring... necessary if you use unprotected cells which are about 2.5mm shorter than the protected versions (e.g. recycled laptop cells as below).
[IMG] 
[/IMG]
The torch I use for work does that. I screw off the lens and usually find the led assembly has come loose. This one has a ring but which you need a circlip pliers (or a Biro) to resecure.
Like said above strap the cels to stop them moving also spray all metal part with wd40 as may have corroded spray them an wipe them then leave to dry for 30 mins should sort it
Also, if it has a tailcap like the one in my pic above, then check that the lockring inside it is tight. There are usually 2 indentations in the lockring so you can tighten with any pointed tool. If the tailcap lockring is loose the light may well switch off altogether.
After several taking apart and reassembling a wad of tin foil between battery and switch has it fixed.
I've an Exposure Flash does that sometimes....