Saw this page:
http://www.advrider.com/forums/showthre ... 225&page=2

This guy is using a stock 990 crank, and 105mm pistons (4mm or ~.160) to gain almost 100cc's over standard 990.
Has anyone done anything like this to an SD-SDR?

I will try to get a hold of the guy to find out how its done, weather some company offers a big bore kit, or if he had the stock jugs sleeved, but would like to see if anyone here has tried it.

I am kicking around the idea of tearing onto the top end of my 07 SD this winter, if this is a somewhat easy mod i may try it.

Keep us posted!! I know I'll be watching this thread like a hawk!

Tornado do hi-comp pistons for the 990 LC8 motor.
In conjunction with their cams, gas flowing and skimming they are guaranteeing an increase of at least 15bhp over an airboxed and akra evo motor
They are (apparently) getting a real rear wheel figure of 145 - 150bhp out of their grass track motors.
This is what I am doing this winter.

I understand that getting much of a bore increase is difficult as the stock liners are not generous so a big bore would include removal of the liner, boring out, fitting of an over sized liner and then reboring.

I can't remember where I saw it but I'm fairly certain someone on this forum said stay away from Tornado and their products. Do you know the company well?

There's always Raph at 2RT,,,high comp pistons and cams,,, and those guy's have been running the stuff they sell,,,,,,seems to me they would know,,,,
http://www.2rteam.fr/2RTeam/2RTeam.uk_f ... erduke.pdf

this just seems like a no brainer, albeit a bit more $$$ than a port & polish http://www.gethoned.com/

ok less than $500usd is actually pretty resonable.....

just looked up the part numbers for the cams, 07 SD vs 08 SDR show the same part number, the valves are different (but we new that) .

The only thing about doing all this is ,,you install high comp pistons,, now,, you really will need to do the connecting rod's to handle more power,,how about the bottom end bearings may have to upgrade that as well,, advance timing,,run race fuel , it's gonna ping without it,,, sounds like you want an RC8,,

I had a conversation with someone at KTM and he said they designed the LC8 motor to take up to 150bhp (crank).
Up to that you should be pretty safe.
I know that there are grass track motors with stock LC8 bottom ends making 150+ at the rear wheel but that is for short periods of time.

I think I will go with the conclusive evidence if thats all right with you

This is new news to me, I was unaware there were flexing and strength issues. If that is the case, then I assume the SRD motors have a higher rate of falure?

As for the higher compression pistons requiring better rods requiring race fuel etc etc etc, I hear this argument a lot, and although it has merit, I think its a bit over reactive when it comes to these motors(most modern cycle motors).

The crank, rod and piston are high quality, and usually very strong, if the motor was built at the factory such that a 10-15% increase in power would cause a failure then it would almost certainly never pass initial testing for durability.

Putting 10-15% more pressure on top of the piston has very little effect on internal parts, as the piston and rod have very high compressive strength. Most mechanical failures of rods/pistons/crank actually happen on the intake stroke, when the crank and rod have to decelerate the piston and then pull it back down.So spinning a motor faster stresses the components way more than putting more pressure on top of the piston.

The new RC8R has 13.5/1 CR, the SD has 11.5/1, granted the RC8R has dual plugs and a firing scheme to deal with the high CR, a lot of factory cars are coming out with 12+/1 CR, so i think there is room to improve the SD there as well.

as for the twisting case and stretching bolts, i need to go research that. If there is an issue, i would hope the KTM, being self proclaimed highest quality in the industry, would do something to remidy the situation.

OK - I have to go with this question: why bother?

It can't possibly be worth the cost, and for a road-going bike, unless you live in a country where you can run it flat out AND you get a buzz from that, 140+ bhp naked bike, kinda pointless. If I wanted that, I'd just buy a Streetfighter, Tuono, or B_King. Wait, did I just type that?

No matter what, the longevity/reliability will be reduced. If nothing else (other than mere strength of materials), heat will be the enemy.

If its gotta be orange, buy an RC8(R), and strip it.

Are we forgetting the SD motor is already a bored out 950 and with that in mind KTM would have originally designed the motor to take the stresses of the 950s power output/Rpm/reciprocating mass etc,

But, increased compression does increase the load on the barrel studs which in turn increases the load on the crankcases which will then increase crankcase flexing, which can cause main bearings to bind leading to early failure or worse stress cracking of the cases themselves,

Then you have the SD base gasket leakage problem which appears to be caused by the barrel studs stretching and crankcase flexing which is only going to be more of a problem with a higher compression ratio, if you also increase the bore size reducing the amount of metal in the barrel wall and fitting a larger heavier piston,
Well I think it will be a case of not will it go bang but when, probably during the dyno runs to set it up

Here a very early thread on tuning and big bores - Dr F was very close to ordering pistons and doing it for himself viewtopic.php?f=1&t=3050&hilit=pistons

I think IF you want to do this you need to start with an 08> SDR motor, I believe KTM have made some improvements to the SDR motor, stronger barrel studs,improved crankcases (locating dowels) and to the main bearings to stop them creeping, gaskets, i think the SDR head gasket is also different... there could be more but without stripping and comparing its impossible to know for sure.........

As far as "why bother?" Really?! i don't even know how to respond, why buy a SD when you could spend thousands less on a moped? Why buy a super-sport camaro when a civic is so much cheaper.......

Ok, i'm being a bit ridiculous, but just to illustrate the point, guys pay $1500-$2000 every day to get 10 more rear HP, and are quite happy they did, are they overheating......not heard that one yet.

The mods I am considering could be done inside that same budget, albeit more time consuming, and could easily gain another 10HP, and more torque, my question is "why not?"

the answers to that are being discussed at length in this thread,biggest "why not" in my mind right now is mainly unknown engine reliability.

and as far as heat is concerned, IMHO that is way down on the list, think about it, how often in normal,even "spirited" riding are you at full throttle for extended amounts of time? its usually on-off-on-off- throttle. If a stock SD cooling system can stand a full day at the track where average speeds are much higher than daily driving, and for longer periods, then adding 5-10% more heat into the system will not cause an issue under normal everyday hooliganism.

Yes and you could go on a diet and loose 5kg be fitter,more healthy and better able to ride, spend the tuning money on saving weight, you could loose 10kg off the weight of the bike, thats more than the equivalent of tuning the motor for 15+ RWBHP