Cannonballs Back Into It With A BT 80

Discussion in '2 Stroke Bicycle Engines & Kits' started by cannonball2, Nov 29, 2016.

  1. cannonball2

    cannonball2 Active Member

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    So winter has come to the Coastal Empire. High yesterday 45. Point is the thing ran the best it has yet. This made it apparent as I suspected the bike is still a bit rich. I have down jetted once. Will have to again before it really warms up.

    Double wheel braking works great. Really cant tell any difference practically speaking with the before and after. This bike had excellent braking with side pulls anyway. Trick is in using good cast BMX calipers, long handles and decent pads.

    Got the bullet tail light I ordered. Fits the character of the bike which seems to be of a 60s genre. Bought a 26" fender set. With the Hookworms the curvature of the tire fits 26s perfectly. Need fenders here in the land of sand even though Hookworms throw less than most tires.

    Finally partially charged the Lipo, only charge to 3.85/cell(15.4v) to keep the voltage reasonable for the 12v system. Really could have gone longer but was off the bike for brake work any way. This thing starts so easily bet it would go a month+ on a charge. For those that handle Lipos this is the way to go to save weight and space.
     
  2. s1rvr15

    s1rvr15 Member

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    Got a question for you, when I replaced my spark plug, the old one looked like I am running rich (black, not brown like it should be); could the dark coloring be a product of how much oil these things need (I run just around 25:1), or should I lean it out? I'm worried about not giving it enough fuel/lubricant and seizing it.
     
  3. cannonball2

    cannonball2 Active Member

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    Running rich wont hurt it the more fuel the more oil for break in. Run it a while on excess oil then change to a leaner oil mix. Use your own judgement there. I ran about 1/2 gallon @25:1, then about the same @32:1. Am now on 40:1 all synthetic. Will run there a while then probably wind up at 50:1. Remember the more oil the leaner the fuel. My carb was excessively rich below 1/2 throttle.

    I got a Chinese 36cc pole saw Friday. Got 50:1 right out of the box and trimmed trees all day. Thinking the bike engine makers figure the more oil the better to keep the stuff together. Doesn't make it so or necessary I'm thinking.
    Once again use your own judgement.
     
  4. s1rvr15

    s1rvr15 Member

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    I think I'll leave it as-is and try leaning it out once it starts warming up. Probably gonna stick to around 25-30:1 for oil for now, call me paranoid, but I've shredded HTs before by going too lean on fuel and oil.
     
  5. cannonball2

    cannonball2 Active Member

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    Best to be conservative. However this is no CG!

    Added a vintage SW top winder speedo. Had the proper drive for 24" wheels. Also installed the 38t sprocket dropping from 41t. This lowered the ratio numerically from 16.4 to 15.2:1. This engine is a torque monster for a 70cc 2stroke. Hardly noticed the ratio change still pulling easily from stand still. Ill bet this would easily pull ratios in the 14s. Checked the speedo with GPS and its 4mph optimistic. GPS showed 34mph tops. This calcs to 7k rpm. As I said earlier its a willing revver stock. Big advantage is it raised the cruise range 4mph.

    Got the 15mm Bing clone. Will need a shim to fit the stock manifold. Thinking one from an SHA will fit. Gotta find my old one packed away some where.
    The stock throttle cable will work.

    So I'm thinking this is a good engine. The kit is very well done if you don't mind hanging all the stuff on the bike and it looks. It has been 100% reliable to date save for the recoil. Dont plan as I did on using it for the main starting source. It has more power out of the box than a CG, more low end, and will rev higher. Its way smoother and has lighting/charging coils as well.

    It does cost more. I bought mine in early December for $269 shipped. Soon it was back to $299 then dropped a bit later to $279. Currently(last time I looked) its back to $299. Kinda like the stock market. Go figure.

    I'm riding this thing daily(pretty hard) so we will see if it hangs together. So far so good.
     

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  6. cannonball2

    cannonball2 Active Member

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    Finally found my extra spark plug wire and terminals.

    I always say if you are gonna go faux go big! The twin plug racing head!

    Also got lucky. With the sprocket change I lost the nearly perfect chain adjustment on both sides. A derailleur sprocket added to the unused chain guard stay solved the problem. I know its on the wrong side of the chain but it works and generally doesn't get pedaled much.
     

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  7. scratchbuilder

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    Lookin good. Dual'in plugs...is that a start button under the seat? I like your speedometer. How do I get one? I'm done with the electronic ones..broke the wire on Two! I've not seen one that reads Upside down. Tensioner worked out great.
     
  8. cannonball2

    cannonball2 Active Member

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    Thanks Scratch!

    Yep that's the starter switch.

    You can find retro style analog speedos all over ebay in the $15+ range. They are Chinese of course. Like everything some are good some aren't. I have had the best luck with the ones that don't have the resettable trip meter only the odometer.

    This speedo is a Stewart Warner, an old American made unit. They are also on ebay and can be pricy. But they work and last. I like the mechanical aspect of it. You loose your mileage and settings on most digital units when the battery dies. Not these.
     
  9. cannonball2

    cannonball2 Active Member

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    This thread was really about the BT80 but it got a build thrown in with it.
    And the build is winding up.

    Got it fendered today. Ordered a real nice set of fenders but they were too wide for the frame after I squeezed the rear triangle together to fit the strange rear wheel. So used a set salvaged from a bike of my wifes, Ignore the color! It will all get paint. Was a real trick bending/fitting the left front stay around the speedo drive. Got a leather tool bag for the starting lipo. Its sitting on top of it, just checking the fit.

    This thing has evolved almost into a proper little M/C.

    Some thoughts:
    Love the BT80(thus far). Like the auto clutch, electric start and lighting system, and the reliability! It likes high gearing.
    Didn't much care for the frame initially but like it very much. Moped front is great. Caliper chain idler is a winner and easy to do! Double brake is strange but works well. Hookworms or similar tires are a must. They ride so well and seem very durable. Like the size of the 24" build.

    All in all its a very nice little bike.

    Last thought. This little engine will rock as a shifter. Has enough revs and torque to make some pretty good speed. Does 34 as a stock single speed, imagine if it had two more(or more)speeds!
     

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    #89 cannonball2, Jan 12, 2017
    Last edited: Jan 12, 2017
  10. cannonball2

    cannonball2 Active Member

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    So riding daily with no issues and having fun with it!

    Considering adding a rack like this. Its for my Vespa but would look early motorcyclish on this bike. Would mount easily using a common older style cruiser luggage rack cut down to fit. They are cheap as dirt from India if you don't mind the wait.

    Its not as big as it looks in the pic for some reason.
     

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  11. curtisfox

    curtisfox Active Member

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    LOL now where did you get that rack form..............Curt
     
  12. s1rvr15

    s1rvr15 Member

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    Looking good! Any idea where I can find some decent 27" fenders to fit narrower wheels? I have some Bontrager ones laying around, but they are mostly plastic and pretty flimsy; eBay has not given many results.
     
  13. cannonball2

    cannonball2 Active Member

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  14. curtisfox

    curtisfox Active Member

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  15. curtisfox

    curtisfox Active Member

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  16. cannonball2

    cannonball2 Active Member

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  17. scratchbuilder

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    That is one nice ride! And light to. Love the fact you hop on, push the button and away you go! Makes me wanna put together the Briggs bike, sell it and order one.
     
  18. cannonball2

    cannonball2 Active Member

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    It is pretty cool Scratch, but keep the Briggs!
     
  19. cannonball2

    cannonball2 Active Member

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    So am wiring the bike for lights The head light is a dual filament sealed beam. Will run only the hi beam. Both filaments are 35w each. The tail is 5w for a total load of 40w. Idea was to run the lights on AC with an AC regulator. For what ever reason I cant pull juice from the lighting coils directly only thru the supplied regulator, which is also a rectifier(converts AC to DC). So will run the regulator.
    I have added a 100v 2400mfd capacitor in parallel to the V regs 12v fused output. This will eliminate flicker in the lights at idle.
    Fabbed an oak mounting board that will mount to an extended stud under the engine out of the way. The oak is a form of vibration damper. Both the V reg and the cap will ground to the stud.

    I had issues using this same set up on my 125cc Lifan build. Would take out bulbs at high revs. I added the same AC regulator(even though its DC) and it solved the problem. Will add this one mounted under the head light. Like where an old Triumph M/C had the Zeiner diode. Lights run all the time the engine is running.

    Could charge the battery. Havent decided on that yet since its a lipo. However the regulated output will never get close to overcharging the 4S pack(16.8v charged). The pack starts the engine just about forever on a charge so will probably not wire it in.
     

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  20. cannonball2

    cannonball2 Active Member

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    So got the bike wired and the lights working in a basic mode.

    The addition of the cap did not work as well as hoped. I thought it would take out more of the ripple effect of the alternator at low revs. Fully charged it would run a 12v test light for nearly a second, so was hoping for a smoother output. No big deal will just remove it.

    Lighting/charge coils are up to the task of running decent old school incandescent lighting. Since the current is rectified I dont see why it wouldn't run LED. Rode a bit last night on our island(a real test, really dark unpaved roads) with no problems. Kind cool to have a bike motor with these capabilities.

    Bought a repro M/C style hi/lo light and horn switch. Will have hi/lo beams and probably a horn. Found out my tail light has a dual filament bulb(was supposed to be single) so will also add a brake light.

    Next thing is to bring the battery into the circuit. Gonna have to ponder/research this being a lipo.
     

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