Never seen that anyone did actually some changes to the 990 engine itself. I mean some kind of more advanced changes, better crank balance and making the crank lighter perhaps, camshafts, pistons, blueprint?. No super duke engine specialists out there, who knows what they doing and doing it well?
Winter is coming, just looking for some project to not spend cold evenings on the sofa... Let's put money talks on the side and talk about what can be done to improve, and not how much it would cost, it doesn't matter at this point.
Do we have any options at all?

Final result probably not worth an effort, besides joy from rebuilding if it is the thing you are after. You will invest a lot of labour hours, money - in return you get marginal increase in hp/Nm and at the same time most probably massive decrease in reliability. This engine is best with modest improvements on intake, exhaust and mapping - all described here more than enough

My bike is SDR 2008 with Yoshi cans, Rotty intake, SAS removed, secondary flies removed, dynoed with TuneECU. Suspension sorted (front Maxton, may rebuild this year for K-Tech, rear Wilbers), STM slipper, Cordona qs (sorted now) and lot more. Just looking what else I can do when weather is not best to ride. Is not about the money, is about satisfaction and keeping myself busy during frosty evenings.
Was suspecting that I can't gain much, but want to hear if anyone tried.

A few have tried engine mods to increase performance. Several have had gas flowed heads done but all reported back that the gains were not worth it. A few others have done more work with compression increases and more radical head and cam work but If I remember none worked out well and at least one self destructed.

On mine the most noticeable change was fitting a full titanium Akra system. This is the wide bored header version mentioned above. That changed the characteristic of the engine and it just seems to want to rev and rev forever.

HMRacing in Edenbridge used to prep the Bracken Superdukes when there was a Battle race series in 2007/8. They still know their stuff so maybe might have some useful advice about gaining the most and what not to do. Also Paul, (ex Bracken), still runs the workshop in South London and he knows a lot about the LC8 engines. PM me if you want his number.

My advice though is to accept that a free breathing and well set up SD motor can chuck out a good 120-130HP reliably, run forever and still be great fun. If you really want significantly more power the best way is to get another bike, or a 1290!

Turbo?

http://www.youtube.com/watch?v=nizM_0Nutu4

Would be fun

Could any one tell be the diameter of the full Ti Ackro header pipes?I'm going to make my own complete exhaust system and I am of the opinion the stock pipes are a little restrictive.I may step them to three different diameters.Also thinking of boring the throttle bodies from 48 to 50.I think the 52 SDR bodies would be too big with the standard heads.Cheers

I will measure them today for you mate.

Haha, no, it is not an issue, but I didn't think about turbo. I have a plan to build cafe racer, that one may be with turbo, as it will be only a bike to go to cafe on Sunday afternoon

I measured the headers on my bike. This is the full Titanium Akra system.

The outside diameter of the headers as they exit the cylinders is 42mm. The place where they are really noticeably different from the stock set up is at the section where the two headers have joined and run up the back of the rear cylinder to the 'Y' piece where they then split into the two pipes to the silencers. At this place the outside diameter is 67mm.

I need to remove the belly pan some time to have a look at my horn, (which has stopped working again). Maybe tomorrow I can get the bike on a stand and measure all the diameters for this system from the cylinder head right through the exhaust.

This is a constant thread on this forum and there is always a lot of debate and conflicting views about the different exhausts for the SD and what effect they have.

All I know is going from standard SD steel headers with Akra. round silencers to then the full titanium system with Evo silencers. ( I never had the standard exhaust as I had the dealer junk it from the crate). I remember the mod to Full system was really noticeable and changed the engine characteristics a lot and I had to get a re map done. With full system it just seems to want to rev more right through the red line in all gears except sixth when it just tops out depending on the wind, road conditions and incline. I know Klinky had the same experience when he fitted his full system too.

What I don't know really, is whether the OE SDR steel headers, (Which are etched with the Akra. logo), are the same spec and dimentions as the Titanium full system. I don't think anyone has run a thorough comparison and analysis. The material from which they are made will make no difference to their performance, only weight saving.

But if they are different specs. then they are different

Well, it doesn't look like there was something like Akrapovic full titanium system for SDR 2008. I was trying to find this out today with my local dealer, and at the end there was no conclusion, but the full system seems to be only for standard SD. He will try to get some info.

Can someone put some light on this? Do any of you have SD R '08 with titanium down pipe, headers and hex akra silencers? My down pipe part number is 611.05.107.000 and it is stainless steel with Akra logo. I found another one for sale, part number 611.05.107.100, which seems to be standard for SD R '11, on the picture both looks the same, but I'm not sure if this will fit my bike and is that stainless or titanium (trying to get some more info at the moment).

Quite a few peeps are having their 1290 SAS/SAR,s done on the ukgser site and after a re map they are throwing out 129bhp
And 87 torkies , sounds awful
Maybe it's the new Euro emissions nonsense ?

I had a Ducati Streetfighter blue-printed, balanced, ported, head and barrels skimmed, flywheel lightened and cams dialled - the sort of thing the OP is talking about (pistons and rods left standard) - and it yielded 20 bhp and 10 lb/ft of torque. And it cost £3500.

Some engines have more left in them to give than others. I don't know about the KTM LC8 mill but the Ducati 1098/11098 Testastretta units are particularly suitable because they have quite a lot of untapped tuning potential. If an engine hasn't much more to give its not worth it unless its to correct known design flaws or component weaknesses. The 1098 Ducati engine had weak main bearings. It was to replace those BEFORE they failed that I went for a blue-print. If you're going to strip and rebuild an engine that is running perfectly to prevent a future problem it would be mad not to blue-print it.
A solid long-lived engine was the objective in my case as much as the performance gains. The amount of gains I got were a bonus but they weren't an accident. They didn't just throw a standard set of enhancements at it without thinking about it. There was a performance brief which was to wind bottom-end and midrange punch up to 11 and the engine was set up specifically with that in mind. they were looking for a particular power nd torque curve at the end of it and I have to say they nailed it.

Unless the 990 engine has that scope for improvement (which I doubt) or unless it has an inbuilt flaw, like weak mains, which needs correcting (and I'm not aware that it has - its a very tough engine) it isn't worth doing unless you like engineering for the sake of it.
I think on the 990 you'd get more bang for the sort of buck I spent by doing induction and ECU uncorking mods and spending the rest on chassis tuning.