Top Speed

Discussion in 'Motorized Bicycle General Discussion' started by kevinkrg6, Aug 9, 2011.

  1. The_Aleman

    The_Aleman New Member

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    When you were growing up, you probably weren't throwing chinese copies of a 1930's-era Soviet engine on your go-karts and minibikes, too.
     
  2. Greg58

    Greg58 Well-Known Member

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    I have a friend that has raced go-carts forever and he gets 18hp out of a 5hp briggs, performance is not cheap. What we are tring to do is make a motorized bicycle haul us around a little better, at a small cost.
     
  3. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    My daily commuter is a Diamondback bike with AVID BB7 203mm disc brakes. Powerplant is a 2.8hp Tanaka 47R engine w/Tanaka 3-piece pipe through a shift kit w/8-speed cassette. Low gear is 37.09:1, which is good for steep parking ramps and gridlocked traffic of steep hills. Cruising 5th gear is 18.55:1 or 6th gear w/16.36:1. Cruising speed is 35-40mph.

    Fear is the limiting speed factor.xct2
     
  4. Scootmeister

    Scootmeister Member

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    Hey 5-7, how well do your gears shift? My latest project has a 7-speed Shimano cassette with grip shift and I can't decide whether to keep it or yank it off. Also, you don't hear much about Tanaka engines. It sounds like you are satisfied with yours. My guess is they are Japanese and of good quality like Hondas (though the Honda 50 is now being made in China). I agree with all of the comments comparing the performance of go-karts to MBs. When I was a kid we used McCullogh and West Bend engines on our karts. These engines were high compression, often boosted with ether, and they had fantastic fully adjustable diaphram carbs. Those engines were so powerful they ate clutches and sprockets for breakfast!! I wonder what karters are running today.
     
  5. atombomb232610

    atombomb232610 New Member

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    heres some pics. i will attempt the gps run on camera later.
     
  6. SlowBalt

    SlowBalt Member

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    I'm up to 48 mph with a 30 tooth with the same engine. I see someone else understands pipe tuneing for top end. We have abought the same gear raito beacouse of the wheel size diference. [​IMG]
     
  7. mapbike

    mapbike Active Member

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    I honestly just dont see how in the heck you're getting those speeds with a 36T sprocket..... but if you are as you say that's pretty incredible and you must be twisting that little Z-80 10,000 RPM's

    I have the same Z-80 engine on a 26" bike with easy rolling wheels and a 36T sprocket, expansion pipe, well tuned DAX RT-15mm carb. shaved head, NGK B6HS plug & nice clean ports, at 38MPH this engine sounds like it is coming apart and stops pulling. it pulls very good to that RPM but is just wound out of itself at the 38MPH mark and vibes are severe at this speed.

    I have another bike that has a 34T sprocket and even more engine work and it has never seen over 41MPH.

    You must really have a jem of an engine there Atombomb232610...

    hope it last a long time for ya..

    Peace, map
     
  8. Scootmeister

    Scootmeister Member

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    Hey Mapbike. I have a Chinagirl and was wondering how she's rated as far as RPMs. Does some brands rev higher? Recently I rebuilt mine and was surprized to find that it only has two piston rings instead of three. Why do they vibrate so at high RPMs? My Homelite bike is smooth at 7K. Must be a balance issue with the crank. Anyway, I was thinking about your comment to Atombomb and don't see how one of these engines could turn 10K when my Honda Nighthawk with 4 big Mikunis doesn't. Anyway, half of the fun of building these bikes is learning what makes them work best. I'm on a new project and I'm trying to decide whether to go with my Chinagirl or my Grubee Whingding 4-stroke.
     
  9. mapbike

    mapbike Active Member

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    Scootmeister,

    Everything I've seen spec wise on these engines shows them to be HP rated at 5000 - 6000 RPM's, and as for the # of rings on the piston having 2 rings is twice as many as many of the smaller 2 smokers have as far as weedeater type engines and such go, they mostly have only 1 piston ring which works great and reduces friction/drag in the cylinder.

    The vibration is due to being poorly balanced, some of the chinagirl engines are better than others but just like the rest of the stuff, you never know if you will get a fairly smooth running one or one that will numb your butt and hands at 3/4 throttle, mine all vibrate at very high WOT RPM's but with 36T sprockets or smaller they will all cruise real nice at 30-34MPH with minimal vibes that are still fairly comfortable for long rides of 15-20 miles, main thing is to just have them mounted very securely and tweak and tune them real nice, you will have a thing of joy when you do, I have a 150cc scooter that will cruise at 50 - 60MPH, I have a 1982 Yamaha XJ650 Maxim that will run a hole in the wind and I still love to just hit the back roads around here on my MB's, there's just something about the MB's that give such a good feeling and a sense of satisfaction from cruising around on something that is different than most people have and something you have put so much time & effort into getting right.

    As to the comment I made about the 10K RPM's I was just throwing that out there......I'm sure he isn't actually turning those kinda R's....

    Yep, lots of trial and error is part of the fun on these MB's, thank goodness we have this great forum to help us skip over a bunch of the ERROR and let us do many of our trials with a good amount of valuable knowledge to help us get many things done and fixed without to much grief most times.

    As to the "Chinagirl or my Grubee Whingding 4-stroke" just depends on what you want, 2 stroke a bit louder, not quite as smooth probably, but more power and speed OR 4 stroke, smoother, a bit quiter, less power, less speed, but probably more dependable from many peoples perspective.

    I dont own one of the 4 strokes so I cant speak from personal exper. but I have some very reliable 2 stroke china girls that I will jump on and go 50-60 miles round trip on and never have a worry in the world about getting back home under power from the engine and NOT the peddles.

    Best wishes for what ever you go with, they both have +'s & -'s like everything else.

    Peace, map


     
  10. andrewflores17

    andrewflores17 New Member

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    40mph on a dax 2stroke with a 36 tooth sprocket on flat ground and a tuned exhaust good plug wasn't impossible on a rare day i did 45mph with wind hill etc i could cruise comfortably at 35 (this is when i wayed 140)

    now on my gebe 30 mph top end 35 no wind and i duck in

    on my 4 stroke 30 tops with a 48 tooth sprocket (RIP 4 banger)

    exhaust exhaust on the two stroke and the sprocket were key for speed im convinced a 4 stroke will only get 35mph top end with out putting more money than its worth into it maybe 40 for someone really light

    i bet a recumbent could do better though
     
  11. young grease monkey

    young grease monkey New Member

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    xct2I got a solid 30 with no mods, but I do have the angle fire head and cns carb. I'm 150 pounds
     
  12. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    QUOTE=Scootmeister;327744]Hey 5-7, how well do your gears shift? My latest project has a 7-speed Shimano cassette with grip shift and I can't decide whether to keep it or yank it off. Also, you don't hear much about Tanaka engines. It sounds like you are satisfied with yours. My guess is they are Japanese and of good quality like Hondas (though the Honda 50 is now being made in China). I agree with all of the comments comparing the performance of go-karts to MBs. When I was a kid we used McCullogh and West Bend engines on our karts. These engines were high compression, often boosted with ether, and they had fantastic fully adjustable diaphram carbs. Those engines were so powerful they ate clutches and sprockets for breakfast!! I wonder what karters are running today.[/QUOTE]

    Scootmeister, they shift as smooth as butter, after I learned to slack the throttle, pedal and shift gears, then get back on the throttle. No broken chains, cassettes or derailleurs after that. The SBP chainring bike sprocket and the 8mm engine chain and sprocket are indestructible. I was worried about the $20 pocketbike tranny's tiny gears and teeth. I've had a tranny seal, circlip and bearing wear out. However, they're so cheap and easy to replace, if and when the time comes. All pocketbike trannies whine in protest, but they hold together. I use automotive grease instead of oil, in the tranny.

    Four mounting bolts hold the engine onto the bike. Disconnect the throttle and killswitch, and the engine falls away from the bike. Remove the transmission shaft sprocket and two more bolts, and the tranny slips off.

    The Tanaka engine is so reliable that you just need to wipe down the oil spray and concentrate on the rest of the bike's maintenance needs.dance1
     
  13. Shorty

    Shorty New Member

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    I put a 28t sprocket (I think it was a crank sprocket for a bmx bike) on my MB today.... Took it for a test run down town and hit 39mph according to my gps speedo. It doesnt sound like its winding out as high now either. Before, with the 44t, I could only hit 26mph MAX with a tail wind, and thats with the motor screaming. I weigh around 160 and have crappy wheel bearing and tires on my bike. If I were to get new bearing and smoother tires, could I conceivably gain a few extra mph's
     

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