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Thread: 2012 ktm sx 150

  1. #1

    Question 2012 ktm sx 150

    Hello all,
    I have been riding four strokes for several years now but am eager to get back on a two stroke, and with a bike like the 150, still being able to race competitively!
    But I have completely forgotten about maintenance, I have read the thread on the 2008 KTM144 and it is apparent you need to keep on top of it.
    So i am just curious, is the 2012 jetting alright (have the problems with the earlier 2007/08 models with them running too lean been ironed out)
    How often should you swap the piston? (using vertex pistons) gaskets? and the bottom end?
    Is there anything else that you need to watch out for?

    Also what are peoples opinions of this bike?

    Many thanks for any replies, regards will

  2. #2
    Moderator RattraySx's Avatar
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    Default Re: 2012 ktm sx 150

    They are very good bikes. The jetting can be lean if your running 40 or 33:1 on the main jet. If you do run those oil ratios the bikes like a big main jet. 185 standard but as big as a 210 is needed in the heavy going. The needle clip like any small bore needs changed every day your out if the weather has changed.

    If your a fairly quick rider I would check the rings every 10 hours and a piston change every 20. If you are fast fast every 5 and 10. Bottom end checked every piston change and once a year get the mains and big end done regardless.

    Gearing wise I think they are a little long and need a tooth up on the rear.

    Suspension I am not sure how the spring rates compare to the older 150's due to the linkage and valving changes this year. But I imagine they will be soft ish and set for a 9.5 to 10.5 stone rider.

    You hear a ton of horror stories but to be honest (I am debating between a 150 or 250 sx 2012 for my next new bike). I know of 5 riders with them and I have helped them a wee bit in maintenance engine & suspension schedule etc and none have failed. Those guys range from back of the pack c rider to a fast a rider and they are used twice a week in general hard going conditions due to the lovely Scottish weather.
    Your only as fast as the last person you pass!!!

  3. #3
    Moderator RattraySx's Avatar
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    Default Re: 2012 ktm sx 150

    All of the 144's do need to be looked after and the TM's and KTM's have come on in the last few years to produce factory 125 power for mass production. It does come with one downside is that maintenance is up a little more. The days of a b rider running a piston all year in a 125 is gone. If you do manage it your running on borrowed time. Same with the 250f's.
    Your only as fast as the last person you pass!!!

  4. #4

    Default Re: 2012 ktm sx 150

    Quote Originally Posted by RattraySx View Post
    They are very good bikes. The jetting can be lean if your running 40 or 33:1 on the main jet. If you do run those oil ratios the bikes like a big main jet. 185 standard but as big as a 210 is needed in the heavy going. The needle clip like any small bore needs changed every day your out if the weather has changed.

    If your a fairly quick rider I would check the rings every 10 hours and a piston change every 20. If you are fast fast every 5 and 10. Bottom end checked every piston change and once a year get the mains and big end done regardless.

    Gearing wise I think they are a little long and need a tooth up on the rear.

    Suspension I am not sure how the spring rates compare to the older 150's due to the linkage and valving changes this year. But I imagine they will be soft ish and set for a 9.5 to 10.5 stone rider.

    You hear a ton of horror stories but to be honest (I am debating between a 150 or 250 sx 2012 for my next new bike). I know of 5 riders with them and I have helped them a wee bit in maintenance engine & suspension schedule etc and none have failed. Those guys range from back of the pack c rider to a fast a rider and they are used twice a week in general hard going conditions due to the lovely Scottish weather.
    As stated if the bikes Jetted correctly and set up for the conditions it will be raced in then these motors are very reliable and should pose no problems, most historical problems are from lean jetting and too much compression - the killer of any two stroke. ie USA jetting specs with poor fuel, wet UK winters in deep mud or sand = detonation and broken 2 stroke, simple. The 144/150 can easily handle the extra load compared to a 125 as its also used as a 200 motor in Enduro reliabley, there used to be a 200 SX version in 2004.

  5. #5

    Default Re: 2012 ktm sx 150

    Thank you very much for the quick reply and the information there is very useful.
    I am a amca expert 11th12th place rider... so regarding the jetting and oil ratios (presume by that you're on about the oil you mix with the fuel!) what would you recommend for both?
    i haven't rode 2 stroke properly since 07, so am very out of touch with the ratios and all of that!!!
    Also, my dad is feeling worried about the two stroke and its ability to keep with 250f's, do you find that the extra few horsepower and bottom end of the 150 allows it to do this?

    many thanks will.

  6. #6

    Default Re: 2012 ktm sx 150

    Quote Originally Posted by Countryboy View Post
    As stated if the bikes Jetted correctly and set up for the conditions it will be raced in then these motors are very reliable and should pose no problems, most historical problems are from lean jetting and too much compression - the killer of any two stroke. ie USA jetting specs with poor fuel, wet UK winters in deep mud or sand = detonation and broken 2 stroke, simple. The 144/150 can easily handle the extra load compared to a 125 as its also used as a 200 motor in Enduro reliabley, there used to be a 200 SX version in 2004.
    Thank you for your input! standard UK summer/winter conditions, in terms of jetting, is there any need to change the jetting week in week out? Is this what all two stroke riders do?

  7. #7
    Moderator RattraySx's Avatar
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    Default Re: 2012 ktm sx 150

    Most of the guys I have helped set up their 150s we have done the following.

    KTM's

    40:1 with your choice of pre mix. Standard pilot playing with the air screw from 1 1/2 turns to 2 turns out to get the bottom end pick up as clean as possible.

    Needle clip position usually standard or 1 groove leaner again for the bottom to mid pick up.

    Main jet around the 205 range (standard 185) so quite a few larger. This produces a slightly darker plug than a perfect tan dry brown but like any small 2 stroke it is safer to run slightly rich on the verge of a wet looking plug in very deep wet sand to help cool the engine.

    Your main jet will stay the same for most part of the year. Same with the needle. The pilot may change every few months depending on the temperature changes. Week to week adjustments are required on the air screw and needle clip position. Takes 5 minutes to adjust and is worth a few hp. A badly jetted small bore 2 stroke running all the mods (pipe, head, porting) will be no quicker than a good jetted standard bike. Jetting is easy to do and once you understand whats going on you will keep your engine pulling hard and running in a safe condition.


    Suspension wise on the 09-11 bikes almost all the riders went up a spring rate both front and rear to get the sag numbers better and dropped 5-10 ml of oil from the outer chamber to get some more plushness out of the forks.

    The 2012's are linkage based and have completely new valving and good stock SKF (I believe) fork seals that should make them a lot plusher. But I imagine the forks will be sprung for around the 10 stone mark and an intermediate rider. You are obviously going quite quick so if your around that weight I would personally go stiffer on the front fork springs and see what sag number you get on the shock before changing the shock spring. Do a setup as per guide at the top of the page before deciding on re valving.

    A couple of the guys put pipes etc on the bike and that gave a healthy boost in the mid to top. Not so much on the over rev. One was a DEP and the other I can't remember.

    All of the riders went up one on the rear (or down 1 on the front and down 2 on the rear) effectively the same gearing. It helped with getting into 3rd gear quicker and allowed a bigger margin of error on the overlap between gears.

    One of the more beginner riders if you like was struggling going from is 250f. We went down 1 on the front and down 1 on the rear (about the same as 2 up on rear) sprockets and he could really lug the bike through the corners more and had 2 gears to choose from in most cornering situations much like a 250f. From then on he was converted.
    Your only as fast as the last person you pass!!!

  8. #8

    Default Re: 2012 ktm sx 150

    Quote Originally Posted by RattraySx View Post
    Most of the guys I have helped set up their 150s we have done the following.



    Main jet around the 205 range (standard 185) so quite a few larger. This produces a slightly darker plug than a perfect tan dry brown but like any small 2 stroke it is safer to run slightly rich on the verge of a wet looking plug in very deep wet sand to help cool the engine.

    Firstly thanks so much for the detailed replies that you are giving me! they really are helpful and you are helping me to understand two stroke jetting! with the 205 main jet that you recommend, you say about deep wet sand, it is a rarity that i would have the pleasure to ride in these conditions and will mostly ride clay/slightly loamy tracks. Is the 205 main jet also suitable for these conditions? and when should these alterations be made? from new... or after the bike has been run in etc!

    will

  9. #9
    Moderator RattraySx's Avatar
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    Default Re: 2012 ktm sx 150

    From new it is worth going up on the main jet before even riding. You get some spare jets in the ktm spares. I think you get a 190 main and a different pilot jet. Not sure if it is leaner or richer though.

    Get yourself a 200/205 main jet to start with. Won't do the bike any harm during riding going to rich. Worst case scenario is a fouled plug.

    Have a wee read at the 2 stroke jetting guide up the top of the page and read from here down.



    "Throttle Ranges:
    Pilot Jet/air screw:0-1/4.
    Needle Jet:1/4-3/4
    Main Jet: 3/4-Full open



    A few things to remember. More oil means leaner plugs (plug will go white). Less oil means richer (plug will be wet).

    The important thing is to get some time on the bike and run it in properly. Do not listen to the brigade that says go flat out on a new bike. It is not just the top end you run in.

    First of all do 1 heat cycle on the stand. That means start with the choke out no throttle, keep the engine ticking over with a few gentle turns of the throttle for 20-30 seconds. Then push the choke back in and keep it going for another 20-30 seconds with the throttle. That will clear its throat. Now feel the top of the radiators. As soon as they get quite hot to the touch stop the bike and let it cool down for 20 mins.

    now start the bike again with the choke for 10 seconds and follow the same as before with the throttle and choke off until the radiators are warmed up. Now jump on the bike and ride away. Keep the bike under load and short shift up through the gears. Turn round and repeat. That is a 2 stroke properly warmed up. Then go run it in (see next paragraph). IMO a minimum of 2 hours with an oil change at 1 hour and then an oil change and air filter at 2 hours. The second hour of running in should be done at faster speeds with the occasional 1 or 2 fast laps every now and then.


    On the first run on flat ground let it rip full throttle up through the gears a couple of times just to seat the rings correctly. After that, ride around the track or field smoothly with the engine under load for the duration of the run as the gear box etc has to run in also.
    Your only as fast as the last person you pass!!!

  10. #10

    Default Re: 2012 ktm sx 150

    [QUOTE=RattraySx;4078213]



    A few things to remember. More oil means leaner plugs (plug will go white). Less oil means richer (plug will be wet).

    [QUOTE]

    I have just finished reading the jetting thread, it is very helpful and i think i stand half a chance of jetting the bike correctly now! just two things, how do you know when the bike is at its 'fastest idle' and two I would have thought more oil in the mix would mean a wetter plug?! Confused aha.

    Also would you recommend putting a putting a 200 jet in, would that suffice? or should i do the shut of test it talks about in the article?

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