I'm doing head port on my SD 990 and gonna put a 52mm SDR throttle bodies. I was looking picture of guys that do it and I found this. What do you think about this porting? valve guide were cutted, no doubt that it a good way to increase flow but what about valve support? ...not recommended?

Go see http://jprecision.com/contact/ get it done right.

I remember someone here doing the full works with hardly any results.
Can't remember who, one of our UK members, best have a look at the tread before comitting to trowing heaps of cash at it.
On the other hand I'm sure there are improvements to be made.

Tripod Dave was the man.

SDR Heads will help more than the throttle bodies I think.

I think part of Daves problem was the fresh nickasil coating in the cylinder bores (can't remember the correct spelling), I don't think it had time to wear in or was not applied correctly... klink had an engine failure not long after his was re-touched also

My problem was not refreshing the top end while I had it all apart. She had done 44k hard-ish miles with a shit load of trckdays by then and I should have used the opportunity to replace the valves ect. She then dropped a valve at 52k miles.

I'd also say part of Dave's problem was that he made so many changes at once. Different pistons, header types, cans, cams ect ect.

I stand corrected. .. carry on.

Either way. .. it was a sad moment

I have heads in the hands, I will be surprise if there's no gains to get there!! Match valve seat with combustion chamber/intake-exhaust port, remove sharp edge lengthen the radius, polish exhaust port, replace the rough casting finish at the intake by a sand blast surface. I got good result by giving more air to this engine, remove 2nd files/shaft and ITG air filter make a great difference so I guest that use a larger throttle bodies like SDR (but its use 3mm larger valve) and head port gonna help too

Ok so:
I gas flowed the heads,
Fitted race cams,
Put breathers into the crank cases and cam covers
Fitted cp carillo high compression pistons
Modified stock throttle bodies, with different velocity stacks
Rc8r throttle bodies
Fitted Akra evo and SDR evo full systems
Tried no airbox, modified stock air boxes and DNA stage 3

I tried pretty much every combination I could think of and the best result I got from a non- SDR motor was 125.5 at the rear wheel with no airbox, Akra evo system and stock throttle bodies with flies removed.
Almost as good with my modded airbox or the DNA.

Of course, if you want to give it a go yourself I have a set of refurbed barrels with £500 worth of cp carillo high comp pistons looking for a good home and I'd even throw in the heads and cams but they're damaged so may not be salvageable. All yours for £250 plus carrage but don't say I didn't warn you!

I also have a set of RC8R 2012 throttle bodies but as above I can't recommend them.

What's wrong with the cams mate?

they ran dry in the head so picked up some damage.
I've had them looked at and they 'may' be salvageable.
It's a shame as they cost me a fortune and they are half the weight of the stock ones.

I'd be interested in them Dave to get them checked and see what can happen.
Are they KTM or tornado?