79cc Preditor on 29" Fatal Love #2

Discussion in 'Photos & Bicycle Builds' started by KCvale, Jul 3, 2015.

  1. KCvale

    KCvale Motorized Bicycle Vendor

    I'm doing another 79cc pred with a Q-matic direct drive.
    This was the first one.


    This where #2 is.


    The custom drilled Q-matic didn't play nice with my custom base so I had to shim the engine up 1" with square steel runners.


    It is farther along than that now but I haven't processed any more pics, it's a double Holiday for me...
    The 4th of July is also my Moms birthday and she's still around.
    She still remembers riding floats when she was a kid, she thought the parade and fireworks were for her for years hehehe ;-}
    rons likes this.

  2. KCvale

    KCvale Motorized Bicycle Vendor

    Engine and drive train in.
    Custom exhaust is on.
    Handlebars done.
    Fuel system done.
    3-brake system, Front and rear independent add-on C-brakes plus the Macargi coaster brake.

    My server being down is killing me.
    I have detailed pics and instruction of how I do the throttle on these and really don't want to re-do design.

    Pics of progress when my server is back up.
  3. KCvale

    KCvale Motorized Bicycle Vendor

    Almost done...

    It still needs the exhaust header painted, a speedometer put on, the throttle kill button hooked up and some zip-ties but it's functionally done.
    My mechanic lives ~15 miles away and has been testing it to and from work this week.



    I ended up cutting off the stock exhaust header just after the bend, then cutting an NON-EPA 2-stroke just right to match them.
    Best I could get was a couple crummy tacks on it, but enough to run it around the corner to Jim's welding and they did a nice job.

    Joe wore a pair of baggy nylon shorts the kids these days wear one day and a leg fluttered into the exhaust.
    That's OK, I am painting the whole header pipe part black, but what a mess, that nylon just melts right one.

    The Q-matic was a real pain.


    In order for the Q-matic to fit the 79cc's head angle Quenton drills new mounting holes that lower the back of the case.
    So low that it is past the bottom of the engine.

    I used a 49cc 4G base, and to raise the engine up from it I used 2 strips of 1" square stock between the base and engine, and longer engine mount bolts.

    Another issue was the stock belt and pulley.

    We couldn't keep the pulley from moving out until we put washers on the shaft to the pulley and an end cab bolt.
    The belt was toast in no time.
    It was hitting the tensioner arm bolt.

    I picked up a replacement belt a tad thinner at CARQUEST around the corner for $5 and all is good now.

    Another issue with these builds is the throttle.
    The engine has a manual throttle with governor and carb has noting but a tab, not even a return spring.

    I stripped all that away and fashioned a metal strip with a hole and notch for the throttle cable, made a mount point for the throttle cable stop, and screwed it to the throttle tab, and put in a return spring.


    This is tricky.
    You have to get the metal tab at a 90 to the throttle tab the exact right length so full throttle on twist gives you full throttle on the carb, and it comes back to idle.

    Works good though.
    You have the full range of throttle control.

    We know it does over 40mph easily on those 29" tires, how much over (Joe thinks 50) we will know when I put a speedo on it today.

    I don't particularly care for builds like this.
    For the hobbyist with the right tools and parts a rewarding ride,
    but for me a money loosing time consuming pain in the butt build.
  4. KCvale

    KCvale Motorized Bicycle Vendor

    This thing is just beating my butt...

    Exhaust weld broke.
    This particular Q-matic is, well, an oversized POS with issues.

    Besides replacing the belt already I need to replace the output sprocket because no matter what chain I try it bucks.
    A sprocket that won't fit any chain I try.

    Why the output sprocket isn't standard 415 is beyond me, but it has made my life miserable this last week even with 41 chain and not feeling any joy at all.

    ANyway, this thing should have been out the door last week yet I am still dicking with this transfer case.
  5. 2old2learn

    2old2learn Member

    Thank goodness for this post. I've been thinking all this time that I'm the only one running into problems building a bike!
  6. KCvale

    KCvale Motorized Bicycle Vendor

    Hehehe ;-}

    There is plenty to be said about tinkering and trying new things, heck my first 3 years in business were all about 'what do I try next?' until I have finally tried most everything, but I'll take a box of parts that play nice together (Also Known As a Kit) over this 'engineer it on your own' every time.

    Kit Directions?
    Heck, we have wrote our own in US English 'best practices' directions that actually work the best right here on this forum and others.

    It's all Do It Yourself, but it REALLY helps to just get a big box with everything you are likely to need, and the flexibility to engineer as needed.

    When I finally get this one perfect and out the door I am changing modes to providing boxes of good stuff for other more realistic smaller 4-stroke builders.
    That news is just days away ;-}
  7. butterbean

    butterbean Well-Known Member

    I honestly don't know why a predator build should be this hard. Is it for a specific customer who didn't want to spring for any upgrades? I am putting a 79cc in a 1956 roadmaster with double top bars and the cylinder fits vertically. There goes your mounting issues. Agk jackshaft, bolt on and go, 35 chain primary, 41 chain secondary. Drivetrain issues gone. Exhaust from agk. Throw on a header brace and that's that. You will need to drill and tap a new oil fill hole. Oh and to mount the engine vertically I simply modified an agk mounting plate to bolt on vertically. Had to notch one side for the chain ring to clear and drill some extra holes for mounting clamps but let's see, jackshaft was 150 shipped, clutch was 40 plus shipping, exhaust was 50 plus shipping I think, and making a new oil fill hole didn't cost me anything. Oh I'm also using a 19mm mikuni carb. Slide type throttle, so no linkage to fab. Only reason my bike is not finished is because I'm waiting on parts I ordered. Its not often anyone would say this to you, but you could've had the bike done and sold already if you just used the right parts bro.
  8. 2old2learn

    2old2learn Member

    Hind sight is always 20/20.

    I'm riding my bike daily weather permitting but it seems every ride I'm discovering something I need to address. My latest challenge is to reroute my exhaust stream from off my buns to the backside of my bike. I've fabbed up a copper exhaust but used silver solder and it keeps failing at my 90 junction where I route it rear wards. Looks like Im going to have to braze it at my two 90 junctions. I'll look around and find one of my contacts with the correct torch equipment. Fortunately I work in the automotive parts industry so I know most of the mechanics in town. Muffler shops come to the top of my list.
  9. KCvale

    KCvale Motorized Bicycle Vendor

    All good points.
    Especially drill and tapping a new engine filler and buying a different carb.
    They have to be the top my list to install an entirely illegal engine on a motorized bike hehehe ;-}

    Naw, not for me bud but I see your point, I could have put even more effort into it and lost more money than I already have but sometimes that is how it goes.

    It turned out nice after I re-did the exhaust though.



    Isn't there someone that sells an exhaust for the 79 Pred for MB use?
  10. butterbean

    butterbean Well-Known Member

    Qmatic is around $300, agk jackshaft is $150 shipped. How exactly is that losing more money? I don't know why you are losing so much money. I've got about a grand all told in my predator build, its gonna be worth two easy when I'm done and if I ever would sell it that's how much I'd ask. Agk sells an exhaust for the predator, as I mentioned in my earlier post.
  11. KCvale

    KCvale Motorized Bicycle Vendor

    Bummer AGC is out of all exhaust pipe stock.
  12. bikejock

    bikejock Member

    I'm looking to upgrade to a 79cc predator and a Qmatic myself from the grubee stuff. After my clutch bell broke off on my China 4G I thought to myself; I'm done with cheap parts. Time to rebuild. How's it fit on the 79cc? I found a predator 79cc for $120 and looking at getting the Qmatic from EZ motorbikes for $300.

    I found out the HS142 is actually a little more than the predator 79cc. The HS142s go for $150 where as the Predator 79cc is a pretty reasonable $120. Heck, their 212cc engines go for $200 on harbor freight. That's a pretty good bang for the buck.
  13. butterbean

    butterbean Well-Known Member

    I got my 79cc for $85 with a 20% off coupon. Check harbor freights website for coupons.
  14. bikejock

    bikejock Member

    Nice! I gotta look into coupons. Do you know where predator engines are made? I'm just curious.
  15. KCvale

    KCvale Motorized Bicycle Vendor

    They are plenty strong, that's for sure.

    There is also an HS 144F that is 53cc.
    The HS's comes with a clutch and the carb is designed for a cable throttle.
    The Pred does not.