79cc Predator 4 stroke on Beach cruiser

Discussion in '4-Stroke Engines' started by ronphelps, Mar 15, 2013.

  1. ronphelps

    ronphelps New Member

    P3150421.jpg Hello, Thought I would put out there What I have been working on. A 79cc Harbor Freight 4 stroke engine not yet finished but very close. Need to hook up the chains and wire the lights that I have installed to be using a 12volt moped battery. Generated off the rear tire with a generator to charge the battery. I should add that most every thing that has been done so far has been ideas that I have borrowed from the internet as well as this forum. I am very thankfull for the forum and the Ideas. I have added some pics. and welcome any new ideas where I should go from here on this Thanks Also I will add more pics as it should be done real soon Will Let the forum know how fast it goes and how reliable it is P2150393.jpg P3150420.jpg P3150422.jpg
    Last edited: Mar 15, 2013

  2. Samdallas214

    Samdallas214 Member

    looks like a lot of time and money went into your sweet MB
  3. professor

    professor Active Member

    Ron, I think you will like the HF79.
    I have that engine on bike number one, I did increase the main jet size a couple of thousandths and this helped eliminate the need to keep the choke on for a long time when cold starting (all these newer engines are jetted lean).
    I disconnected the governor, the engine power goes flat at about 5 grand.
  4. ronphelps

    ronphelps New Member

    Hello, Yes I think I like the 79cc HFso much that I bought a second one for a spare. Really cheap easy to get. and fits on bike easy. I also removed the gov. on this one. I do have a lot of time and money in this but mostly from trial and error mistakes like the 80cc kit. also wondering if this is right and that. Got to the point of just doing it right or wrong without a kit basicly fairly easy. I cut my teeth on this one and still have plans for the 6.5 HF> It should be MUCH easier this time. I have a better idea .Thanks Professor
  5. EZMJon

    EZMJon Member

    What clutch are you using?
  6. ronphelps

    ronphelps New Member

    Hello I'm using a 5/8 Bore Max torque clutch with #35 chain and 11 tooth sprocket on clutch
  7. ronphelps

    ronphelps New Member

    Short update on Build

    Hello, Here is an update on my 79cc predator bike cruiser build , I have had up to 40mph and that is PLENTY for me on this bike I have some vibration issues but after a steady speed is reached it's fine. Here are some new pics as well thanks P5130499.jpg P5130497.jpg
  8. sawdust

    sawdust Member

    why did you run the exhaust pipe all the way around to the other side of bike instead just straight back on the same side? Am I missing something here?
  9. powerstroke

    powerstroke Member

    Looks like he wanted to use that exhaust rather than the stock exhaust that it comes with (which sucks).. but this was too long just to stuck out from behind him so he wrapped it around and now its perfect.
  10. ronphelps

    ronphelps New Member

    OK, to answer your ?. I copied the work from a youtube video and there explanation made good sense. The upward slant of the intake would bring the pipe up and then down which would look awkward. Also there are the chain and sprocket going on there. It wasn't that hard to make, used an old shopping cart tubing for the natural bending and added length as needed. also there's the ten dollar muffler added on the end works real good. I think it looks cool looping around. make sure it's braced good. Any way most of the work was copied and adjusted. Learned as much as I can from this forum and you tube.
  11. birdmannn101

    birdmannn101 Member

    Love your build Ron, I bought an exhaust with muffler for $32 including shipping but after putting it on the bike I could see me burning my leg if I moved myleg back.

    P0009449.jpg P0009450.jpg

    So, what I ended up doing was cutting off the flange on the exhaust pipe and also cutting off the the exhaust flange on the muffler that came with the 79 engine and welding the 2 pieces together. It looks good. Hope it rides good.

    P0009453.jpg P0009455.jpg
  12. professor

    professor Active Member

    Looks good guys, but make sure you put a heat shield over any bit of pipe that possibly can come in contact with YOU!
    It doesn't need to be fancy/ the more air space between it and you- the better.
  13. birdmannn101

    birdmannn101 Member

    Professor, where might some one find some heat shield material?
  14. professor

    professor Active Member

    There is no material per say that is heat shield stuff. Cars use a metal plate over the cat converter to deflect heat - under it too. They stamp it out of sheet metal. we make it out of whatever.
    (Looking at your pic, I would place that pipe in toward the frame as much as possible- quite a bit more than you have)

    I cut some sheet metal in a shape to cover my exhaust, then pounded it into a rounded shape to conform somewhat to the pipe. The whole shield looks like a big S. It is attached it with nuts welded to the pipe and bolts thru the shield.

    (I have used hose clamps to attach shielding on tractors- you just need to deform the metal down from the shield to form an air gap.)

    If that is not enough (wasn't for me) I put some expanded metal in strategic places to protect me- like this-

    Attached Files:

    Last edited: May 15, 2013
  15. darwin

    darwin Well-Known Member

    That pipe is close, too close! I see some well done rockie mountain oysters in your future.
  16. Barry

    Barry Member

    I'm collecting parts right now for my next build using a 1961 Schwinn Jaguar frame, found a great handmade fuel tank that will go between the crossbars, and I've ordered the Preditor from Harbour Freight. I'm pondering using 1" copper pipe for the exhaust, whaddaya think?
  17. professor

    professor Active Member

    Barry, I suppose it would work if you silver solder or screw the connections. Heat is an issue for normal solder. I use steel tubing.
  18. atombikes

    atombikes Member

  19. birdmannn101

    birdmannn101 Member

    Yes it did get in the way of the transmission. I should have mounted it first that way I could have tilted it up in the rear and have to re-weld the exhaust pipe twice. Here is what it ended up looking like.

    P0009487.jpg P0009488.jpg P0009489.jpg

    I bought a Harley heat shield for $1.39 and put that over the muffler.
  20. ronphelps

    ronphelps New Member

    Update of 79cc predator cruiser

    Hello, Your bike is looking really good, I don't think I have seen any two bikes alike on this forum. Here is an update of my build I started last year, I put in all the lights "working" 12 volt moped battery, Blinkers, headlight, taillight, brake light. and repainted the gas tank with Motobike sticker. I think I am finally done The bike goes about 35 with no problems

    Attached Files: