60 MPH...achieveable? Who cares?!? Let blueprint an engine!

Discussion in 'Motorized Bicycle General Discussion' started by DVBikes, Mar 18, 2010.

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  1. Creative Engineering

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    For those who have just hopped on to this thread...

    Page 15...posts 142, 145, and 149 will bring you up to date.

    Crank bearings?

    What about the crank bearings & the seals?

    They must be bad...right?

    Not so fast there skippy...let's have a look at reality for a moment.

    There are very few bearing manufacturers on the the planet. In order to stay competitive in a global market certain ISO, (Interntional Standards Organization), standards must be adhered to. The fact that this is a cheap Chinese Bicycle engine does not mean that there is a cheap Chinese bicycle engine bearing manufacturer. Given the capital outlay for a bearing plant, and the fact that a high volume is critical to success...there's not even the slightest chance that the crank bearings in these engines are sub-par!

    Soooo...A few junior engineers have decided that the deluxe replacement is a dimensionally correct, "sealed" SKF bearing.

    Certainly no one can dispute the quality of SKF bearings...but I will argue that it is best to purchase them open ended, and use the Chinese factory seals!

    The spec catalog seal is actually a dust cover...it is not, nor was it ever intended to be a "seal" against internal pressure...the kind of pressure that is normal with a 2-cycle engine.

    See the attached photos...

    I was able to remove the dust seal, easily, with a pick. It would have popped out, almost instantly, under the pressure of a 2-cycle engine running.

    The first pic shows one bearing with the dust cover...and another with the dust cover removed.

    The second pic shows a profile of the bearing dust cover...and the difference between a "seal" and a dust cover.

    Jim
     

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    #201 Creative Engineering, Apr 3, 2010
    Last edited: Apr 3, 2010
  2. Creative Engineering

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    If you own...or have access to...a machine shop...then certainly follow along and make some improvements to your engine. Otherwise I would not recommend dismantling your engine. You will gain nothing but a pile of parts.

    Jim
     
  3. Easy Rider

    Easy Rider Santa Cruz Scooter Works

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    Jim, Back when I use to rebuild my high reving BZMs. I use to remove the seals on the crank bearings. I found out that when I left them on the bearings my crank bearings would not get enough lubrication and evenually blow up from the heat. I'm not sure but doesn't the HT motors have crank seals that fit into the cases?
     
  4. rockhopper

    rockhopper New Member

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    Mine is a project for my Uncle. I'm supplying the donor bike and pitching in on half the job.

    He is an engineer and mechanic and has access to his own machine shop. He'll be thrilled to hear he needs to rip the thing apart. Will have to turn him on to this thread and forum. He's very new to the internet.

    Thanks for everything, Jim. I'll hang back and watch.

    Looking forward to your results.
     
  5. Flight Risk

    Flight Risk Member

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    Thanks for the explanation Joe. I'm starting to get in the know with these engines.
    And Jim, your explanation of the Chinese factories is interesting also. I've been wondering how there are so many brands of engines, yet all the replacement parts are pretty much interchangeable.

    Rod S
     
  6. Creative Engineering

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    Yes, the seals press into the case on each side of the crank. I had wondered the same thing...I was thinking that even if the bearings were positively sealed, would there be enough volume for the mix to adequately cool and lube the bearings. Your post confirms that thought.

    Over the years I've rebuilt quite a few 2-strokes, and as far as I can remember they've always had separate bearings and seals.

    Jim
     
  7. Creative Engineering

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    This is the bike we plan on using for the engine test.

    It is a worksman that has been built using the best components they offer. It's a really nice, heavy duty, bike.

    The wheels were assembled using upgraded rims, and 11Ga. spokes. The front drum brake works great! I haven't checked yet, but I'm certain the front hub is running on conventional ball bearings instead of the caged ball type. The tires are Kevlar belted.

    I haven't checked yet, but I don't think anything will need to be upgraded. DV is 6' tall, so we will probably use a layback seat post. The wheels will be trued using a dial indicator...the tires will also have to be trued, and then each wheel balanced.

    Thanks go to Justin for supplying this bike.

    Jim
     

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  8. Creative Engineering

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    Thanks for the thumbs up ausped,

    I think we'll find out that a little machine work will go a long way towards improving the overall performance of this engine!

    Jim
     
  9. exavid

    exavid New Member

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    I had an experience with crankshaft seals on a two stroke in the early '60s. It was on a Yamaha 175 motorcycle. Apparently it had originally been purchased in Japan by a US serviceman because parts weren't available in the US and its speedo was in kph. By the time I got it many miles had been rung up on it. It would only start if we towed it with a car or another bike. Once it started it would run at high rpms but if you slowed it down it would quit. After eliminating any problems with ignition and carburetion it appeared that bad seals were allowing crank case pressure to be so low at low rpms that there was very little suction through the carbs. When you tow started the engine it seems that the pressure changes in the crankcase happened so fast that there wasn't enough time for the pressure to fall that low and the engine would run fairly well. Unfortunately at the time I lived in an Eskimo village in NW Alaska and in those pre-internet days finding parts was impossible.
     
  10. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    I didn't feel like reading the whole thread. Did the OP get 60? Or is he road pizza?
     
  11. DVBikes

    DVBikes New Member

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    lol im road pizza lol no we havent finished
     
  12. troyboy

    troyboy Your East Coast Gasbike Connection

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    Your Welcome..

    Justin
     
  13. Creative Engineering

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    Pablo...there will be no road pizza on my watch! I've been doing this kind of thing for far too long for any sort of disaster to come from this build.

    Read through the thread some...you might enjoy it!

    Jim
     
  14. azbill

    azbill Active Member

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    I am not sure of the worksman drum, but my Sturmey-Archer X-FD has sealed bearings, so I would expect yours to be high quality as well
     
  15. weekend-fun

    weekend-fun New Member

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    *drools* that bike... She's a beaut' :D
     
  16. rockhopper

    rockhopper New Member

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    Considering the weight of the donor bike I'm thinking the fairing will play an important part in this project. That and gearing.

    Just a guess from a standard, "naked" motorcycle rider.

    The biggest impediment to speed to me while while riding my DR650 is that the rider acts as a reverse sail. And I'm kind of a big sail. Working on it, though.
     
    #216 rockhopper, Apr 5, 2010
    Last edited: Apr 5, 2010
  17. rockhopper

    rockhopper New Member

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    In my little uninformed mind I can imagine my mountain bike gears being twice their size. I would pedal furiously to get the speed up to 20 mph to engage first gear. And then we go from there.

    Yeah, I'm clueless. But this is a fun thread.

    Good luck, Jim and DV.
     
  18. Charged-Reacter

    Charged-Reacter New Member

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    Yes the worksman bikes are heavy duty but the real question is what speed does
    this bicycle stays stable at. Lets take a look at the Maui Downhiller bike. This worksman bike
    goes downhill for 38 miles in Maui without a motor and speeds up to 30 knots or 34.6 miles
    per hour with risk involved. I am sure that 60 plus could be obtianed but no one over there
    is that foolish. Add a motor to get going at 60mph and there is no safety margin. Save it for
    the salt flats in Bonnieville is where it belongs.
     
  19. rockhopper

    rockhopper New Member

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    Bump for a thread that has 7,387 views.

    Stable, shmable. Aren't there lightweight road racing bikes that do these speeds downhill already? What's the problem?

    Put the fairing on it, bolt up a set of gears that has a top gear that's 24", get DV a full set of leathers and full face helmet, and ride.

    I'll pitch in some money if need be.

    Ha ha!
     
    #219 rockhopper, Apr 6, 2010
    Last edited: Apr 6, 2010
  20. rockhopper

    rockhopper New Member

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    10 more views right there...

    We're pulling for you guys...

    OK, the 24" gear is a stretch, but you get the idea.
     
    #220 rockhopper, Apr 6, 2010
    Last edited: Apr 6, 2010
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