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How to get more power from two stroke (KTM125)

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Hello, i have a 2008 KTM 125sx. i bought the bike brand new and it is still in prestine condition. After riding season was over i stripped the bike and went through all the components. cleaned the carb, cleaned the airfilter, did the routine oil change, purchased a new rear tire and Renthal gold chain along with a few other cosmetic uprgades. and also lubed and lock tighted everything needed. So the bike is in perfect functioning condition. The bike performs and looks great however, i was looking for a little more gonads. So i got a new FMF Turbinecore 2 silencer. sounds great and performs a little better. but i was wandering if anyone had success stories of how they got significant more power out of their two stroke. Also, keep in mind the jetting is working great, The bike starts good and pulls steady hot or cold, and it has good compression and spark. If you have any comments or suggestions on the bike please reply. Thank you

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It looks like you have done all the mods......time to trade in on a 150 (great reveiws) or a 200cc?

There is only so much one can do to max the power without compromising ride-ability!!

Why not get the 250 xc-w .......e start & still light weight?:thumbsup:

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To borrow a famous quote: "No replacement for displacement!"

The laws of physics and thermal dynamics can only generate so much power from machine expected to run more than a few seconds (i.e. jap drag cars that put out over 1000 hp). Time to move up in displacement!

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The only cost effective way to get more power is to buy a bigger bike. There are a lot of things you could spend money on, but they offer minimal power increases and make the bike less reliable. I keep my 125 totally stock, and use it for play riding and the occasional HS race. It's very reliable, easy on parts like tires, brakes, and chains, and more fun to ride than my 250.

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bull malarky. It depends on how much more you want. Your best money spent, and these really should be done anyway is setting X dim to 0 (almost free), head cut ($90), then if you still want more, port the jug (approx $350). That will give you more grunt and power everywhere.

The key to power is getting air/fuel burnt and thru the engine as efficiently as possible. These mods do that.

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It's also worth while to do some PV experimenting. Depending on where you like the "hit", this is another really good free "mod" too.

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Thank you, i am not complaining of the bikes power, i love the way it performs and handles. But a little more power can never hurt. Now for gmoss, if you could tell me a little more about your first two suggestions. i don't understand what they are. and as far as porting the jug, i have thought of that. but, i'm going to wait until i need to spend the money on a new top end for spending the big bucks on jug piston head rings the whole nine yards. also, i was worried that with too big of bore, this may affect my crank wear on bearings in the future. and i dread the headache of matching the jetting to the new bore. Thanks again.

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I have been on two strokes for years but never have experimented with the power valve. Its intimidating to me, especially on my KTM because it has so many components. how affective is learning how to Adjust it?

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get a fmf header that will add more and jeff slavins from slavins racing will do a port and polish. he has been doing it for years and will do a great job. other than that theres not much you can do maby put a power now and power now pluss in there

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read my how to in the FAQ for adjusting the PV, its easy on the 125/200.

For more power as Gmoss said and add to that stuffing the crank. Cutting the head gives more compression and, if done by the right person, may improve the burn of the fuel, both give more power.

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About the power now and power now plus. now i'm not extremely familiar with this upgrade but i think that its the valves that you can get to insert in front or behind the carbs depending on if its power now or power now plus. i looked online and can only find the powernow for my model ( 08 125sx ) but. for a hundred dollars, is this mod worth the money? how significant is the power change?

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The 125 doesn't have different types of pv springs does it? isn't that only on the 250?

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Does anyone here have a prefered set-up as far as how much to deck off the head/base gasket thickness? Just picked up a 125sx myself and I'm pretty much in the same boat with all the bolt-on mods done! Thanks!

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First of all, we are not talking about an overbore. We are talking about porting the intake and exhaust track in the cylinder. Slavens does very good work.

Here's a quote from RB Designs, good information:

Head milling is more than just raising compression, it's a way to help your engine breath, burn more of the fuel mixture and help cool. All of this will give you better snap, rev and torque with great reliability.

The squish band is a very important part of head mods and this is where I spend a lot of time. Just getting the proper squish band without going overboard on the compression will give great results. "HORSE POWER" and "RELIABILITY".

Adusting the PV on the 125/200 is extremely easy. There's lots of information in the FAQ, pictorials also.

Setting X to 0 refers to the top of the piston at TDC in comparison to the top of the bore in the cylinder. Setting it at 0, (usually it sits below the top which decreases compression, increasing squish gap), will help compression and performance. Done by adjusting the thickness of the base gaskets.

IMO, first to last

X to 0

adjust PV

head cut

port and polish

then pipe etc.

The Powernows are nothing but a gimmick. They don't make more power, just move it around. But, that may be what you want.

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ya know, I am curious as to how much can be gained by head and jug mods on the 125. hmm :thumbsup:

How much less can I get by with......

good threads on the 125 here lately.

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Yes, I'm curious as well. For example, maintaining the stock bore and stroke, how much do you think you would have to do to get a 125 KTM to reach the performance of the 150 SX?

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Yes, I'm curious as well. For example, maintaining the stock bore and stroke, how much do you think you would have to do to get a 125 KTM to reach the performance of the 150 SX?

my 200 has had some mild porting, and will have the head cut soon. The mild porting has helped, but I can't wait to see what the head does, and would also like to see what a real port job would do.

If bottom end gains can be had, then I would possibly consider one. Of course, I can always stuff the bottom end at a last resort. I think it could get close, but lack some of the grunt of the 200.

I guarantee it could be a very fun, functional bike, even for a heavyweight like myself, as long as it will pull my butt up the hills. lol

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You guys all are helping me a lot with the info and iIve heard of some new things. Thank you very much for all the threads.

I plan on getting a 144 bore and head work done in the future.

but for now i am still confused on setting x dim to 0 and adjusting the power valve.

as a beginner mechanic you guys are more advanced than i. could i get some more info on instruction? thanks.

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