new HT bike

Discussion in 'Frame Mounted Engines' started by JunkyardDog, Apr 26, 2011.

  1. JunkyardDog

    JunkyardDog Active Member

    These things are addictive. First I built a rear friction drive bike using a BMP kit and Robin-Subaru motor, and it still runs great well after 1000 miles. Am on my second rear tire, but it still has plenty of tread left.

    Then I built an electric bike using parts from, that will take me over 10 miles without pedaling (why put a motor on a bike if you are going to pedal?) it is also running just fine.

    Now I want to do one more, this time an HT engine kit on some kind of beach cruiser. I already had the bikes to build the other two, but will need to buy a new bike for this one. Again I need opinions, which is the best kit to use, and the best bike? I fully expect this to cost more than $350, simply because you can't get a decent bike for that. I am on the heavy side, and have problems with broken rear wheels. I am wondering whether or not to get a high quality bike like a Worksman, or get a cheap bike and get a super strong rear wheel for it. (I already know not to mess with the Chinese made wheels for motorized bikes, I would have the wheel built by a bike shop out of high quality parts). I also know not to use fenders, and have heard about all the problems with rear coaster brakes. I may just run without a rear brake, and use a good front caliper brake. I won't be racing this thing.

    Ok, I've been giving this some more thought, and realized that the Chinese engine kits have a lot of issues, that would seem easy to solve. I plan on welding tank and engine mounts to the frame, doing away with the clamps, so everything fits perfectly. I also intend to solve the problem with the cheesy clamp on chain tensioner that so often gets sucked into the rear wheel. I was looking at my old '79 Yamaha MX175, and it has a heavy duty (made for a motorcycle) spring loaded chain tensioner, that does not use any kind of wheel or bearings, but a heavy bracket with a heavy plastic rubbing block on it. I'm thinking to weld a heavy bracket onto the bicycle frame, and bolt this thing to it. It is wide enough that even if the chain has considerable side to side play, it won't be a problem. And there is no way this thing is going to break. It was designed for a dirt bike with a 520 chain.

    The only problem left is how to attach the sprocket to the rear wheel. I have not figured that one out yet, I intend to use a high end disc brake rear wheel designed for a downhill mountain bike. From looking at the parts, it looks like I can machine a special adapter to mount to the disc brake mounts to mount the sprocket to. I know adapters already exist, but they mostly use clamps, other than the "made to motorize" rear wheels which have threaded on sprockets. This is a good idea, but the quality of these wheels leave a lot to be desired IMO. When I am done, the only Chinese part on the bike should be the engine, which I consider disposable. A properly built bike could go through several engines.

    For as long as these engine kits have been around (and I do think they are a good value for the money) it surprises me that someone has not solved these issues, and built a high quality motorized bike, with no clamp on parts. Maybe there just isn't any interest, and people are satisfied with what is available. I am by no means an engineer, but I am a mechanic and a pretty decent welder, and this is not exactly rocket science. I would like to build a true "motorcycle" out of one of these kits.
    Last edited: Apr 26, 2011

  2. DuctTapedGoat

    DuctTapedGoat Member

    I started running my rear wheel via disc brake rotors less than a week ago - I'm liking the results, but the alignment is a bit off when rolling backwards. The tensioner straightened it out enough for forward operation, which is enough for me - knowing it's solid and that my wheel isn't going to break down 40 miles from home.
  3. bluegoatwoods

    bluegoatwoods Well-Known Member

    I'm not enough of a mechanic/engineer to comment of specifics.

    But viewing the engine itself as disposable and bringing the rest of the bike and drive-line up to your own specs seems like a good strategy.

    You'll probably end up with a nice bike. Good luck.