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Thread: Just bought 70cc SR 50, tuning questions!!

  1. #46
    apriliaforum newb
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    hey guys the yasuni kit perfect and we derestricted it!

    now with the specs from the 1st post (now there is a 90 main jet) and yasuni exhaust...what do you guys recommend for tranny?? i know its a hit or miss and trial and error but who has what set up close to the specs i have currently?

    of course the tranny may be fine, just have to re tune to fit the new exhaust...

    i think we are finally getting close this has been a mission and head ache!

  2. #47
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    Hey All,

    so bike is back at peak power again like it used too!! After all this time and money we finally got it... bike does 60mph all day long!! Here are current specs

    21mm carb
    90 main
    38 pilot
    stock air box and filter
    Yasuni exhaust
    malossi 70cc kit
    no clue what is in tranny?? been the same since i had it
    starts off slow then mid range pulls hard and top range slowly reaches 60mph

    all in all its back to normal runs and idles very well, the only little issue now is its a pain in the ass to start (guess it all cant be perfect) not sure why but almost feel like its not getting enough fuel even with choke on to fire? it has new plug and ngk wire and cap...and it tends to run a little hot..amazing how much of a nightmare this thing has been...

    any feedback? suggestions? recommendations for start up and future mods? thanks for all the help and input guys!!

  3. #48
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    Hello everyone this threead is great so much info. But I also have a 2001 sr50 with the malossi 70kit installed with a 19mm carb and stock airbox with malossi filter and a lee pipe (hand made TT) version. I started with a 70 main jetand it just spit and sputtered , raised the needle and got worse. changed jets went to a larger jet got worse now iam back done to where I started it sounds like no matter what jet/needle hieght i run it just spitts and sputters after 1/4-1/2 throttle its reall starting to piss me of tbh(lol) I never had this much problems trying to tune a 2 stroke before.I personally think the 19mm carb is way to small for this 70kit and will go to a 21(oko flatslide) I had raced a 2004 honda NSR50 for many years with a 65cc metrakit top and with a 21mm carb and it was the easiest thing to tune. any suggestion would be great. Iam to the point that Iam just going to see the thing and buy something else
    matt davis

  4. #49
    apriliaforum Junkie
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    19mm is not too small. Well Im guessing youre not running a high end stuff there.

    Cleaned the carb and filter? Tried without the airbox?

    How about the choke? Maybe its stuck?
    Aprilia SR 50 2008 Silver Crowd
    Aprilia RS 50 2003 SBK Replica

  5. #50
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    High end stuff? Leo Vince is a good pipe and a deloroto carb is not good? And yes I cleaned the carb and the choke and removed air box this is not my first time trying to tune a 2 stroke


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    matt davis

  6. #51
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    i think you need an open filter period. if you take note of the slide number and needle number we can think more on it.
    ---
    as far as i know all the phbg carbs are setup for open filters. and arraksa is right the 19mm carb has 20 percent more cfm than you will ever use furthering the setup problems somewhat.
    ---
    its simple thermodynamics that fits in a fortune cookie - carb should be 80 percent of the exhaust outlet size as a starting point for open filters.

    i assume you have the minarelli/morini/aprilia engine not the newer piaggio?
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  7. #52
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    Quote Originally Posted by hndaman1 View Post
    High end stuff? Leo Vince is a good pipe and a deloroto carb is not good? And yes I cleaned the carb and the choke and removed air box this is not my first time trying to tune a 2 stroke


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    In scooter world high end means real hp. You have some kind of low sport setup.

    Why ask if you know everything about two strokes? youd thought one could get it going if thats the case.
    Aprilia SR 50 2008 Silver Crowd
    Aprilia RS 50 2003 SBK Replica

  8. #53
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    Quote Originally Posted by sublunacy View Post
    i think you need an open filter period. if you take note of the slide number and needle number we can think more on it.
    ---
    as far as i know all the phbg carbs are setup for open filters. and arraksa is right the 19mm carb has 20 percent more cfm than you will ever use furthering the setup problems somewhat.
    ---
    its simple thermodynamics that fits in a fortune cookie - carb should be 80 percent of the exhaust outlet size as a starting point for open filters.

    i assume you have the minarelli/morini/aprilia engine not the newer piaggio?


    Yes I have the Morini engine with a malossi kit running a ngk br9hs plug. The carb is deloroto 19mm started with a 70 main jet and the needle all the way down.the air box has a malossi filter and the air box was modified per the filter install instructions, I was told to stay away from pod type filters.


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    matt davis

  9. #54
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    ok - pod filters are louder than your exhaust.

    ----
    if you want to make it work there is a long list of tuning parts to get the carb plus air restrictor/box to match up. it will be a long and expensive job. in the end not a single carb needle will be 100 percent. all the phbg needles are very unlike what an airbox needle looks like. getting frustrated yet?
    if you had a geniune phva with the piaggio a22 needle it would have been perfect with a 17.5mm restrictor. that is still alot of work.... i am pushing a delorto/dakar 15mm on another member for price and decibels/ im waiting to hear back if he can get it tuned like a champ. the reasons are plentifull but mostly that carb comes with a covered filter and its very very compact.
    Last edited by sublunacy; 05-30-2017 at 02:13 PM.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  10. #55
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    It also has the stock reeds in it would you recommend carbon ones? And where do I get them from? Are they the same ones that go in the zuma ? I had a keeway factory 50 awhile back that had a mineralii engine and most of the zuma parts fit


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    matt davis

  11. #56
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    all reeds stink. rotory valve is king. just sayin. mostly reeds are a teeter-totter. more topend/less low end.

    ---
    the vforce reeds are the best setup but expensive. the malossi replacement reeds for the stock valve are the best value.

    -------
    dont worry about specific power too much. ask questions here and get it running kick ass everywhere.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  12. #57
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    to fix up your carb situation. i would try doubling the airbox snorkel tubes. then perhaps a third one then you should be ok to try a 34 idle/86 main. in that area anyway.

    the 38 idle/pilot jet is two sizes too big.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  13. #58
    apriliaforum newb
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    The air box has multiple holes drilled in it per the malossi filter installation kit I am add more holes . Thank you for your help..I also have a kymco super 9s that my fiancé rides around with the mineralli engine, derestricted and does 55mph with her on it


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    matt davis

  14. #59
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    your just building a sub-woofer/speaker box.

    ---
    get some rubber tubes that will fit in the holes and cut them ~ maybe take the diameter and double or triple it for the length. or make something up like atleast an inch long anyway.
    ~ you can get a tight fit.
    ~1/2"- 3/4" inner diameter tubing would be nice for sound quality as a guess.
    Last edited by sublunacy; 05-31-2017 at 12:30 PM.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  15. #60
    apriliaforum newb
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    Well the 19mm carb I had was the issue switched to a deloroto 19mm race carb and it fired right up I installed a malossi type pod filter and a 86 main jet needle at #1 position, and it flies just need to install an outwares filter cover yet..


    Sent from my iPhone using Tapatalk
    matt davis

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