CT-70HK1 Ignition (again, I know. Sorry)

Discussion in 'Tech Area' started by TAWPTool, Nov 8, 2018.

  1. ctbale

    ctbale Member

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    Hey Guy after seeing your pictures I have a question.

    So it looks like you used an original 4 speed honda lower end. I have the same sitting on the bench trying to figure out what to do with it. Looking for a cylinder/piston/head combination that will work. Got some help coming my way but I am curious what piston did you use? Looks like you have a E22 head? Here is my thread. Maybe we can continue the Q&A over there to we dont muddy the subjects. Thanks for your help.
    https://lilhonda.com/index.php?threads/china-top-end.21981/
     
  2. racerx

    racerx Administrator
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    If I've missed something, by all means say so. There's no difference between any CT70 top end made from 1969 to 1981, other than casting numbers...same 47mm bore, "short" rod and taller (compression height) piston combo, with the "old" dome configuration. 12v used a longer connecting rod with matching shorter (compression height) piston. If you use a 12v piston with a 6v (short rod) crank, the piston will sit too far below deck height, at TDC, and you'll have low compression.
     
  3. ctbale

    ctbale Member

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    The issue I was worried about is when you have a short rod crank, with the original taller dome piston, and you try to put on a china head which (I think) has a shallow area/combustion chamber (post 1981 style) the old dome piston hits the valves?
     
  4. Roy Chambers

    Roy Chambers Member

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    Did you also notice that it say's 49 CC's on the Cylinder?
    Thanks Roy.
     
  5. ctbale

    ctbale Member

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  6. kirrbby

    kirrbby Well-Known Member

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    Ya but post #38 says he bought a Zoomzoom complete kit...which is supposed to fit every CT70 ever made, and for only $54 .
    I don't think that is the E22 head.
     
  7. ctbale

    ctbale Member

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    yea, the zoomzoom kit has the flat top piston, will only give you 80psi when using a "short crank" motor. Then you will run into the same problems mk2davis did. then he said a domed piston hits the valves in the china head. I dont think this the zoomzoom kit has a E22 head. Not for $54

    I have this kit coming but if I install it on my short rod motor, gunna have 80psi. Basically same as zoomzoom.

    https://www.ebay.com/itm/Cylinder-Head-Piston-Gaskets-For-Honda-ATC70-CRF70-CT70-TRX70-XR70-S65-70CC-US/362397995714?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

    The seller gave me $29 back to keep it. Seller knows it will be low compression, most likely has had many complaints.

    Gunna use the kit, but gunna mill down the top of a domed piston so it wont hit the valves
     
    #27 ctbale, Nov 11, 2018
    Last edited: Nov 11, 2018
  8. OLD CT

    OLD CT Well-Known Member

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    Looks like the cheap china head strikes again. :LOL: It's not a ignition problem! Check the compression TAWPTool.
    Cheap isn't good and good isn't cheap. Doubt that ''grinding'' on it will work ctbale.
     
  9. ctbale

    ctbale Member

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    Do you doubt my grinding skills? lolhahalol
     
  10. OLD CT

    OLD CT Well-Known Member

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    Doubt you are using a Sunnen, most likley a Drem mill????????? LOL!:D
     
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  11. kirrbby

    kirrbby Well-Known Member

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    Lololol...I laugh at that every time I read it. Good one Pat!!
     
  12. dirtbkr188

    dirtbkr188 Active Member

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    I'll just leave these here...

    FpNh13.gif

    3Ismwo.jpg

    It isn't a Sunnen or a Drem-mill, but hey, it works...lol
     
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  13. cjpayne

    cjpayne Well-Known Member

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    Just vigorously scrape it back n forth on some rough cement.lol
     
  14. ctbale

    ctbale Member

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    I am gunna use that tool on my bench ..... round on each end .... says something about dont grind alum .... ???

    .......or maybe a lathe :)

    or put it in a vice and hit it with a 4" grinding wheel!
     

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