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Thread: 85mm stroke crank, need help

  1. #31
    apriliaforum Junkie
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    Wide open and then gave it a phew kick start too. Didnt rise from that 90 psi. Ill take some pictures whden i remove the head so you can see where the piston sit ats top position.
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  2. #32
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    do you have a reed valve spacer to lower the primary compression?

    perhaps removing the base gasket in favour of case sealant will bring the secondary compression up.

    ---
    perhaps a cylinder like a trophy 70cc and reed spacer or two.
    --- diploma for engine repair in 2012 ---

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    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.

  3. #33
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    Maybe the best way would be take off some material from the spacer that sits between block and cylinder.

    Reed valve assembly and intake are all oem stock.
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  4. #34
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    did it run before you took it apart? can you check for spark again?
    --- 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.

  5. #35
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    Here are the pictures. Hope they tell something. For my eye the piston does not sit too low. its a brand new piston, only spinned when tried to start this thing. OEM head with oem gasket. oem cylinder with 10 000km on it.

    It has not run since my 70cc blew up and took it apart to install these orginal parts to get it fixed.
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  6. #36
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    that looks good.

    it looks real good. it seems removing the base gasket will take it to far and hit the head.

    ---
    it looks like a longer stroke crank? the piston at the bottom looks lower than normal- the top dead center looks great thou.....

    i guess it is stroked 2.5mm and a 5mm longer rod. the cylinder looks fine where it sits.

    ~ what about the reed valve????????
    --- 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. #37
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    is it still apart?? i can help you port that cylinder and bring it up to sport class output?
    --- 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.

  8. #38
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    Stroke should be the same. Only shaft should be longer. With the spacer it should be normal situation.

    I do not want to touch this cylinder. Only make it run again.

    As far as i have checked the reeds. They work fine. Oem factory part.
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  9. #39
    Honest always, feared often Micah / AF1 Racing's Avatar
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    I am truly hoping you mean 85mm rod because 85mm stroke is about right for a 500cc single?
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  10. #40
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    Quote Originally Posted by Micah / AF1 Racing View Post
    I am truly hoping you mean 85mm rod because 85mm stroke is about right for a 500cc single?
    What do you think? even tho I have made the same mistake before. Must be somekind of a lost in translation for me.

    I really am running out of ideas. I guess I could do a spark video. If that seems ok. Well all I can do is to take the engine out and assembly with oem crank.
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  11. #41
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    so here is the spark video. mobile quality, sorry for that. Cylinder head is off on this video.
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  12. #42
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    Quote Originally Posted by Ärräksä View Post




    Here are the pictures. Hope they tell something. For my eye the piston does not sit too low. its a brand new piston, only spinned when tried to start this thing. OEM head with oem gasket. oem cylinder with 10 000km on it.

    It has not run since my 70cc blew up and took it apart to install these orginal parts to get it fixed.
    it looks very dry. if you dont want to try dumping fuel down its throat again / then i guess your out of options.
    --- 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. #43
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    It seems that this is a total mystery. No one has a clue and Ive asked around plenty.

    Only thing I can think now is to assembly it with the stock crank. Makes no sense why that would help but I have no other means on this machine.
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  14. #44
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    i would be happy if you throw the head back on and try to start it again. no need to fill the coolant/ or overtighten the nuts.

    -- i picture a spray bottle filled with fuel and the gas tank unhooked / dissconnected. then spray the carb inlet.

    im 8000 miles away so its just a suggestion. it would take less than 20 minutes to try again.
    --- 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. #45
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    Quote Originally Posted by sublunacy View Post
    i would be happy if you throw the head back on and try to start it again. no need to fill the coolant/ or overtighten the nuts.

    -- i picture a spray bottle filled with fuel and the gas tank unhooked / dissconnected. then spray the carb inlet.

    im 8000 miles away so its just a suggestion. it would take less than 20 minutes to try again.
    Or would a starting fluid be even better? If I took off the carb and reedvalve and spray it straight to cylinder? If that shit doesnt ignite it well nothing does.
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