harbor freight 79cc oil filler threads

Discussion in '4 Stroke Bicycle Engines & Kits' started by atombikes, Aug 4, 2013.

  1. atombikes

    atombikes New Member

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    Thinking real hard about mounting my 79cc Greyhound engine vertically. Have the mounts, fabbed up a plywood plate, etc. But I am stuck on drilling and tapping the second oil filler hole. I have seen others use what appears to be a brass hose barb looking thing- are those 3/4" MHT threads?

    Since I'm not a thread guru, I could use some direction on what fitting(s) to get and what type tap to get.

    Thanks.
     
  2. chainmaker

    chainmaker Active Member

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    Just take your current plug down to the hardware or whatever. match that plug to a bolt to use for the one you just took out , now you know the size. Home depot sells taps get the one you need.
     
    #2 chainmaker, Aug 4, 2013
    Last edited: Aug 4, 2013
  3. culvercityclassic

    culvercityclassic Well-Known Member

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    This is what I used hope this helps you out. The brass fittings should be in the garden section.
     

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  4. atombikes

    atombikes New Member

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    chainmaker,

    Thanks, your advice makes sense. But rather than starting from scratch I was hoping to find out what others have done.

    CCC,

    Thanks for your parts info. So based on the tap shown, your threads are 1/2". On my engine, that recess in the molded boss appears to be more like 3/4" inside diameter. Did you only tap the bottom of the recess, or the side walls?

    I'll go the Home Depot tomorrow and check out their selection.

    Thanks again.
     
  5. scotto-

    scotto- Custom 4-Stroke Bike Builder

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    It's 1/2" pipe thread, use fittings that accommodate.

    [​IMG]

    [​IMG]

    I use mine for a crank case breather and the oil filler as well. It works very well and is simple to use.
     
  6. culvercityclassic

    culvercityclassic Well-Known Member

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    This is it....1/2 pipe
     

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  7. atombikes

    atombikes New Member

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    OK, so at Home Depot I found two garden hose adapters in the plumbing dept. Both are listed as "3/4" MHT (male hose thread) on one end. But on the other end, one is "1/2 NPT" and one is "3/4 in MIP- tapped 1/2 in FIP". I bought both (sorry for the crappy pic of the one). Also bought a cap.

    I'm assuming FIP means female threads...so probably going to take that one back.

    [​IMG]

    [​IMG]
     
  8. culvercityclassic

    culvercityclassic Well-Known Member

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    That first picture is the one you want....
     
  9. atombikes

    atombikes New Member

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    alright, I think I am in business! Thanks guys for the assistance. Of course I still need to do the work, but at least I have the parts.

    [​IMG]
     
  10. runnermike

    runnermike Member

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    I am curious about this mod. What is the purpose? Crank case breather? Oil fill? I am only asking because I am getting ready to start a HF 79cc build.....

    This will be my first 4 stroke build as well.....
     
  11. culvercityclassic

    culvercityclassic Well-Known Member

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    How are you mounting the motor, that would be the deciding factor if that item is needed. Vertical you would need it to add oil. You can vent the motor at the valve cover.
     
  12. runnermike

    runnermike Member

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    I am mounting the motor with the agk mounting plate. I wanted to mount it vertically, but my down tube is 1.65". Andy (Headtrama) was going to make me some mounts, but since they do not make the "rail buggy" clamps in that size I will just be mounting it with a traditional mounting plate.
     
  13. culvercityclassic

    culvercityclassic Well-Known Member

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    Your good to go Mike, no need to add it...one less expense which is good, now you can spend it on the agk intake and 19mm carb, trust me it will be worth it.
     
  14. runnermike

    runnermike Member

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    I have already ordered it! Lol. Don't be surprised if I hit you up for some advice when I actually begin building.....
     
  15. runnermike

    runnermike Member

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    Quick question CCC.....when the engine arrives, besides removing the governor, I remove the stock exhaust, carb, gas tank, AND the throttle linkage???? Only asking since I will be using the 19mm carb and intake, as well as, agk exhaust.....
     
  16. culvercityclassic

    culvercityclassic Well-Known Member

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  17. runnermike

    runnermike Member

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  18. atombikes

    atombikes New Member

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    Edited my post because I didn't see there was a whole second page of good answers to your question....
     
    #18 atombikes, Oct 8, 2013
    Last edited: Oct 8, 2013
  19. Jamesgregory

    Jamesgregory New Member

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    I'm wondering if you drill out the metal and then tap it, What about the shavings that fall inside the motor? How do you get them out because wont they destroy the motor from the inside??
     
  20. Donavan321

    Donavan321 New Member

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    You'd have to remove the crankcase cover after draining the oil(some shavings would come out with the oil, then use a soft rag to get the rest out, reassemble and then refill with fresh oil. Just my two cents.
     

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