Apologies for dipping my toe into this part of the forum I've always liked the st4s in the senna grey type paint but never liked the headlight that is shared with the st2 that looks like a wide mouth frog, preferring more the vfr style headlight of the st3. I was going to ask if it was possible to transfer over the upper fairing of the 3 to the 4. today however I saw a very late st4s with the vfr styled headlight of the st3. did they officially change the st4 wide mouth frog headlight to the st3 style and if so from what year?
Others may have more definite information, but I believe the ST3 style was indeed a very late update for the 4s. Fitting this to an earlier model would involve pretty substantial changes, since the side fairing panels, internal mounting brackets, and many other details of the mounting are quite different.
Change was made 2005 for ST4s. The other feature of the frog is that it is about as bright as Piers Morgan. Guy over on the US forum used to do after market job for around 400 us but does not make them now
Personally I prefer the look of the earlier models, but their headlights do not have a good reputation. Though I had an ST2 and currently have an ST3 I very rarely ride on unlit roads (apart from the occasional motorway) so can't really comment on comparative effectiveness.
I found this from 2004 so presume this is the type you mean? https://www.webbikeworld.com/ducati-designs-ducati-st-headlight/
My Peugeot moped from nearly 50 years ago had a better headlight than the 900ss and the ST4s i had, but great great bikes.
I asked not only because the st4 with the 3 headlight appeals to me but i also saw this converted 4 https://www.ebay.co.uk/itm/Ducati-ST4S/303223344155?hash=item4699850c1b:g:34QAAOSwfHpdGxzq
I have done a number of ST2 conversions, for the one my wife had and for mates ST2s. Not a difficult job, but the look remains the same.
When the ST4 was replaced with the ST3 I believe the ST4s got the ST3 'soulless Jap' headlight I think the 'frog' headlight isn't the prettiest and not the best after dusk but looks different to Japanese bikes. I also believe the new fairings are easier to get off which would be a bonus - not as good as a 916 but you don't have to start by removing the clock surrounds and mirrors
It's not just the headlight shape that is different on the ST3 from the earlier ST2/4. The ST3 (and late ST4S) headlight can be adjusted from the speedometer - although I think every ST3 owner only ever uses it once in their first week or two of ownership. After that you only ever muck around with buttons on the speedometer to change the readout from miles to km when crossing the channel, or change the clock between GMT and BST. The lower an mid fairings on the STs are the same, but the upper fairings have different mounts and the mirror stalks are shorter and curved on a ST3. You probably could fit a ST3 upper fairing and headlight on a ST4 but you would need to change the subframe that mounts the headlight, change the mirror stalks and springs (but you can reuse the mirrors). But the inside panel that surrounds the speedo and tacho on the ST4 is an entirely different shape so that would need a custom panel made. Finally the handlebars are different, so I'm not entirely sure if they would foul the fairing. Much easier to buy a 2005 ST4S
They're not in my experience, the BCDs are slightly different between 2/4/4S and 3/3S and series two 4S. I have a right hand lower fairing panel in my garage from an early ST2 that just wouldn't fit my old ST3 properly.
