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Thread: ATC70, needs top end rebuild - questions!

  1. #1
    Join Date
    Oct 2019
    Location
    Canada
    --
    99

    ATC70, needs top end rebuild - questions!

    Bought a 1985 ATC70. Burns oil, compression is approx. 105 with the throttle open.
    Specification is up to 170 PSI.

    Would like to keep it all Honda, but can anyone comment on the Chinese top end kits - cylinder/piston/head ? And of the Chinese variety, is there a kit that is better than others? Tempting, if they're decent, reliable, and an all in one kit has it's appeal.

    Haven't taken it apart yet, was thinking possibly just a hone/ring/gasket job if everything else was decent.

    Thanks!

  2. #2
    Join Date
    Jun 2009
    Location
    Leander TX
    --
    2,219
    I put an 88cc cylinder and piston kit from DRATV on a TRX70 a few years back. An excellent $100 spent.

    I lapped the valves at the same time. I believe the 88 kit came with all the gaskets including new valve seals if needed.

    Thing ran awesome - amazing how much difference a few cc made.

  3. #3
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Thanks. So, using that kit, you retain the original cylinder head? Any other mods required (carb, head, etc.)?

    Was lapping the valves as simple as seating them with the lapping compound?

  4. #4
    Join Date
    Jun 2010
    Location
    Cold Lake, Alberta, Canada
    --
    3,001
    I bought a complete chinese-ium cylinder, piston, rings, wrist pin and gaskets for under a 100 to my door; and in Canada to boot! The original head was retained with lapped valves. Direct bolt on and is still working good all these years
    Trikes
    1970/71 US 90 (Aquarius Blue)
    1970/71 US 90 (Future Project)
    1972/73 US 90 Camo Project (110 Big Bore)
    1972/73 US 90 Green
    1977 ATC 90 w/83 110 motor (Fugly)
    1982 ATC 70
    1983 ATC 70 (Ladybug)
    1973 ATC 70

    1965 Marketeer 3 Wheel Golf Cart with 1986 Honda 250 drivetrain

    TF 2015

    Other
    1983 Honda Z50
    1978 Honda XL75

    Feedback http://www.3wheelerworld.com/showthr...ck-for-coopool
    http://www.3wheelerworld.com/showthr...k-for-coolpool

  5. #5
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Coolpool, did you go 88cc, or stock bore?

    Haven't pulled it apart yet, but will soon!

  6. #6
    Join Date
    Jun 2009
    Location
    Leander TX
    --
    2,219
    Yes, I used original head.

    Yes, I lapped with lapping compound on the valve and seat, a drop of oil on the guide, and seat the valves with a bunch of back and forth rotation until the valve and seat are pretty and seal verified.

    I bumped my main jet one size. Not sure if it was needed or not. It ran great and I never looked at the plug again.

    Quote Originally Posted by Baba Yaga View Post
    Thanks. So, using that kit, you retain the original cylinder head? Any other mods required (carb, head, etc.)?

    Was lapping the valves as simple as seating them with the lapping compound?

  7. #7
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    Sounds like an easy swap to add a little more power. Does anybody else besides DrATV sell the 88cc kits?

  8. #8
    Join Date
    Jul 2003
    Location
    indiana
    --
    891
    Tbolt usa sells the 88 Kits, multiple options. I have the full "race" variant. Different head, intake, carb. Carb sucks, will be replacing it with a mikuni at some point. I have one of the klx kits on another bike, and it ran and still runs great right out of the Chinese box. Didn't even have to jet the carb.

  9. #9
    Join Date
    Oct 2019
    Location
    Canada
    --
    99
    I think I'll order one up, but just the piston & cylinder kit.

    Thanks all!

  10. #10
    Join Date
    Jun 2010
    Location
    Cold Lake, Alberta, Canada
    --
    3,001
    Sorry baba, a little late to the question; stock configuration only.
    Trikes
    1970/71 US 90 (Aquarius Blue)
    1970/71 US 90 (Future Project)
    1972/73 US 90 Camo Project (110 Big Bore)
    1972/73 US 90 Green
    1977 ATC 90 w/83 110 motor (Fugly)
    1982 ATC 70
    1983 ATC 70 (Ladybug)
    1973 ATC 70

    1965 Marketeer 3 Wheel Golf Cart with 1986 Honda 250 drivetrain

    TF 2015

    Other
    1983 Honda Z50
    1978 Honda XL75

    Feedback http://www.3wheelerworld.com/showthr...ck-for-coopool
    http://www.3wheelerworld.com/showthr...k-for-coolpool

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