1. 2 Stroke Husqvarna Motorcycles Made In Italy - About 1989 to 2014
    WR = 2st Enduro & CR = 2st Cross

125-200cc Sm 125 mechanic power valve

Discussion in '2 Stroke' started by prjctmrx, Jan 30, 2020.

  1. prjctmrx Husqvarna
    C Class

    Location:
    Czech republic
    Husqvarna Motorcycle:
    SM 125 07
    Hello, i've been thinking, since my eletric power valve motor is broken (possibly the potenciometer as many other) is there any way to convert sm engine to mechanical/pneumatic power valve control? I know that it would be possible to change the right side clutch cover and the arms and get the wr barrel. But i was scrolling on youtube and this came up. Some kind of spring and just a cable. Has anyone tried it? I've been trying it for two days now, but seems that it doesn't work for me. Seems that most Italians use this method. If anyone has some suggestions i would appreciate. I can link the video if necessary..

    Attached Files:

  2. speelmanis Husqvarna

    Husqvarna Motorcycle:
    WRE 125 '10
    I was wondering this too. As my 2008 wre one is acting up I saw a video with a guy who just cut a cable and attached a spring to it. Have no idea how to get it to work though
  3. 2strokebloke Husqvarna
    C Class

    Husqvarna Motorcycle:
    wre 125
    Other Motorcycles:
    motorhispania ryz50
    I have done this and it is certainly possible @speelmanis in fact it is possible to truly convert a wre to a cr/ wr as I will detail below for anyone interested who comes across this thread as the info on this is next to none. don’t bother with doing the cable mod as it causes the power valve to open with the throttle and not with the revs as it should , meaning that it won’t work properly. As for the pneumatic power valve - the main crankcase on the wre is identical to the wr/cr meaning that the side casing of the wr/cr can be swapped onto the wre motor - this means no oil pump - the only way to get this part Is off of a blown cr/wr motor or as a very expensive spare part - the side casing is a direct swap with the power valve governor fitting into the oil pump bearing.

    The only other decent option is by buying the power valve membrane kit off of https://www.htmracing.it/prodotti-m...ri-ricambi-husqvarna-sms-sm-wre-wr-cr-125-2t/ its expensive but the easy solution and it works the power valve properly, (the site is Italian but paste the link into google translate and it’ll show it in English)
  4. 2strokebloke Husqvarna
    C Class

    Husqvarna Motorcycle:
    wre 125
    Other Motorcycles:
    motorhispania ryz50
    Now for the rest of the conversion for anyone interested, with the mechanical power valve the cr/wr cylinder will fit straight onto the engine and attach to be power valve assembly- this means also fitting cr/wr water hoses as they are different than the wre/sms ones.

    As previously stated the main crankcase is exactly the same as the cr/wr so the cr/wr crank and gearbox of your choice should slot straight in and the balance shaft can be removed. To finish bringing the engine up to spec fit a vforce v3 reed block and larger intake boot. also fit the cr/wr spec mikuni tmx 38mm flatslide carb

    Now for the frame - the suspension is different but will slot straight in with no issues , the cr/wr swingarms are slightly different from each other but both are aluminium and a huge weight saving from the steel one that’s stock - the subframes on the cr/wr are both the same and are again aluminium but both are a direct swap.

    Now for the hard part - the electrics , luckily the crankcases for cr/wr/wre/sms are the same and haven’t changed since 1998 much any model year of electrics SHOULD work (though I haven’t tested it) the cr electronics have a more aggressive power curve and makes more power but is very aggressive and peaky , the wr can support full lighting , provides slightly less power and is a flatter curve making it smoother.

    Simply buy the appropriate cr/wr cdi , stator and rectifier and hook it up to the coil on the wre/sms already, the wre/ sms voltage regulator cannot be used as the larger airbox doesn’t accommodate the oil pump reservoir so no battery can be used.

    There you have it - it’s a lot of hassle but I can confim it works I did all of the above steps using cr125 parts and electrics , the suspension change isn’t needed unless you plan on riding off road a lot , and I have found that the wre/sms gearbox without balance shaft Is best for road use and doesn’t lose power in any noticeable way.

    Hope to have helped , any mistakes please point them out to me and I will amend them
  5. toni Husqvarna
    A Class

    Husqvarna Motorcycle:
    sms 125 07
    Other Motorcycles:
    none
    Hi, may I be a bit late but. I've had a husqvarna sms 125 for four years now and I spend last one studying how to tune it and having max power (and making the project itself). If you can fit a complete wiring and stator from the wr, i would go for that, still have lights nd a decent curve despite i've mountes a htm rotor (pvl style) with no lights as I know enough electric wiring to make a harness from scratch, the curve is very good, instant power.

    Cilinder on sms and wre is 2mm lower than a wr/cr so the whole distribution is more every day frindly and doesn't need that much manteinance as their competition sisters. if you raise the cylinder, still the chamber cc and shape is different (i'm not 100 %sure, but i would bet are not the same, as many 2 stroke books ensure the dome is very very critical on how the bike gives power or how much power can develop, easy go is the vhm head, (I haven't mout it but i will).

    Critical point do not port the bottom end. The engine of husqvarnas is considered a piece of engineering, and it may seem like the shape it isn't very good is all thought. I did port it and after that i taught with a local prep. used to prep this engines for karting and he told me the bottom end was never touched, i'm about to buy some cranck cases stock.

    Exhaust: Scalvini is the one i like the most but fmf, doma racing, bud racing, etc. All very good exhaust sty away from the gianelli and arrow.

    Cylinder porting: I woldn't modify its shape but clean fundition defects, and polish the exhaust.

    Exhaust valve: as I mentioned before, i got rid of the wiring wirh that the power valve was deleted in Imounted thed the pneumatic from htm racing, despite is a bit expensive for what it is (aprilia rs exhaust valve with a case), totally worth it. I was sick of the problems this valve gave me.

    Don't remove the balance shaft, it isn't worth the bike has no comfort, and on the road that vibrations are a bit annoying.

    I haven't test it on the dyno, I don't know what to guess on hp, as I decompressed a bit the primary compression and the dome isn't a good shape in my opinion (optimal 11,2 cc3) mine isn't there. And I haven't reced any other husq, in spain aren't very common.

    If you have some doubt, you know just text here .hope i helped
  6. Hooosk Husqvarna
    AA Class

    Location:
    Sydney Australia
    Husqvarna Motorcycle:
    wr360 2002
    Other Motorcycles:
    None