long intro

Discussion in 'Introduce Yourself' started by emdude, Dec 7, 2008.

  1. emdude

    emdude Member

    Hi All:

    Well, it said in the rules that I have to post here first, so here it is:

    Having grown up in Europe where as a young person all you could ride was 50 cc mopeds the idea of a motorized bicycle brings back memories and and some sense of nostalgia. With the price of gasoline being what it was lately (better now) and the fact that I live in a small town in Arizona now, the thought of getting some type of moped or small scooter was on my mind for while. Then I saw this guy a few weeks ago riding a motorized bike and thought "man that could be cool". After investigating this a bit and finding the craze has taken off I realized: "Man this IS cool".

    I love the fact that it's a DIY thing with endless possibilities and am real happy about the fact that for the most part government bureaucracy has deciced to stay out of it.

    I have not yet built a bike. I did buy an engine, the usual Chinese one though and it's already half apart on my work bench. I was so intrigued by the pure simplicity of the thing I just had to investigate it. I was particularly interested in the ignition system, spark generation and any possible spark advance they may have engineered into it.

    The mopeds I was familiar with during my very young years did not have any form of ignition advance. Ignition timing was a static adjustment dictated by the setting of a plate in magneto assembly and the opening of the points. The engines always had the same amount of pre-ignition and the best you could do is find the best amount of advance for your engine and riding conditions.

    The Chinese engine I have, probably pretty much the same as everyone else's
    does have a pretty spiffy no point's ignition system. It also has several degrees of static advance. Ignition timing is set by the exact position of the magnet rotor relative to the magneto coil. If you look at the position of the magnet relative to the coil with the piston TDC you'll see what I mean. I wonder if the magnet is "key'd" onto the crankshaft or if there is any possible adjustment should one want to make any. Anybody know?

    If it is keyed, the only way to adjust the timing would be by changing the relative position of the magneto coil. I suppose this could be done. And maybe some on this list have figured all this out already. Guess I'll find out after searching a bit.

    After looking at my new engine a bit yesterday I have a few observations. First of all mine was definitely test run. Which is a good thing I suppose. I pulled the head because I just had to know what it looked like inside and it was full of residual oil from what was clearly a test run. Of course one of the cylinder studs decided to come out instead of just the nut coming off. I decided to pull the entire cylinder. After that I noticed another stud loose side so I tightened all 4 real good into the case. They must put these things together in a real hurry.

    The fastener quality one my engine is not too good. Every nut and washer are pretty much bottom of the barrel and I would think some better items from the local hardware store could be a worthy upgrade. The studs were particularly bad but I'm not sure how exactly to get something better in there.

    At this point I wont worry about it and just install the engine and see what happens.

    Further observations:

    I am impressed with the cleverness of the overall design but really wonder just how long these engines might go. The fit of the cylinder onto the crankcase and the head on the cylinder is quite sloppy. Since the piston is just slightly out of the top of the cylinder at TDC, the whole assembly has to be carefully adjusted with regards to the aluminum head gasket and head while tightening everything down, other wise the piston will actually hit either the gasket or maybe even the head. I doubt this is something only peculiar to my engine and strongly advise any one having taken the head off for any reason to ensure the engine turns over smoothly before running it. I could also see where this might lead to engine failure if the head bolts ever came loose enough to allow the cylinder or head to slip even just a little bit. Keep the head bolts tightened and check often I guess.

    The ports in the cylinder are pretty good size. I did find though that the cylinder to crank case gasket blocks a LOT of the transfer ports. It isn't cut that well to mach. I could even see where the edges of the gasket were slightly bent and frayed from the test run. I could see where after some running time these might wear off to the metal edge opening up the transfer ports. This could account for some of the reported power increase after engine break in.

    The piston looked OK to me but the rings were different from what I've ever seen before. The rings are not shiny as in "chromed". They are black, quite stiff and I can only imagine some type of high carbon steel. Hey, whatever works I guess.

    Well, I have yet to find a bike to install the engine in. I keep looking at the local thrift stores and garage sales but so far no luck. Maybe everybody else around here had the same idea and used bikes will now become rare and rise in price like gasoline.

    I've got my eye on that $90 Huffy cruiser they have at Walmrt if all else fails. I think I read on the forum that someone actually used this model so it must work OK.

    BTW, I like that low volt winding off the magneto on the white wire, makes for some interesting possibilities regarding lighting and even a tachometer I guess.

    That's it for now.



  2. srdavo

    srdavo Active Member

    Hi emdude,
    Welcome to MBc.

    that is quite the thorough inspection on your new engine.

    yes.... the magnet is keyed to the crankshaft.

    yes... all the hardware is very low quality. you are correct about keeping everything tight & checking often. it gets better as you break it in.

    If you decide to use the $90 huffy.... for youy Safety, reinforce your front fender mounting. do a Search for "cranbrook fender".
    the Huffy downtube is also a larger diameter...it's best NOT to drill the downtube, as the chinese instructions may instruct. there are many ways to mount without drilling.

    looking forward to seeing your bike come together......enjoy the forum

    and again.....Welcome.
  3. bluegoatwoods

    bluegoatwoods Well-Known Member

    Hello emdude and welcome aboard.

    You must be a bit of an "investigator" by temperament, huh? That could be useful to you; you have a good understanding of the construction of your engine before even riding it.

    And there are more than a handful of those Huffy cruisers motorized. There is one train of thought saying that those bikes are just not good enough. But I don't think I agree.
    In a moderately long life of almost constant bicycle riding I've had both quality bikes (one really cost a fortune. And I rode it for a long time. A good bike) and "bargain basement" types. And I've found that I get along with the cheap bikes just fine.
    I mostly ride pretty gently and I'm not very heavy (about 180 lbs). I have a feeling that those are two necessary conditions for making the cheap bikes work. But I think those are the only two.

    And the Cranbrook does make a great looking MB.

    Have fun and we'll see you around.
  4. srdavo

    srdavo Active Member

    Yes....so true.....

    but, there are documented Safety issues with the Cranbrook front fender.
  5. bluegoatwoods

    bluegoatwoods Well-Known Member

    Yup, srdavo, you're right for stressing it. So I'll second it.

    You'll definitely want to reinforce that fender. And you might as well pay a bit of attention to the rear as well.
  6. emdude

    emdude Member

    cranbrook fender?

    Hi guys:

    Thanx for the heads up on the fender of the cranbrook, my potential bike for the project.

    But what exactly is needed, some type of bracket to reinforce the fender or what.

    Also, if this bike does in fact have a downtube that is to large to mount the engine directly to, and I agree that drilling the tube is a bad idea, what workarounds have been successfully used? Id there something someone has worked out that I can buy? Or something known to work I can easily make?

    And while I'm at it:

    I don't really like the tank that much and thought it might be nice to integrate a tank into a luggage rack over the rear wheel. Anyone know if this has been done?


  7. beast775

    beast775 Guest

    hello emdude

    maybe you should try craigslist in your area?you can buy a cruiser type frame 20-60 bucks,that has the necessary downtubes for motor placement.and v brakes front and back.it makes it easy for upgrades later.great intro.
  8. Happy Valley

    Happy Valley Active Member

    Welcome to the forum!

    To the question on tanks. Yes, a lot. A simple search on that will bring up quite a few discussions.

    Good luck, you've found a great resource of info contained herein.
  9. Mountainman

    Mountainman Active Member

    welcome -- enjoyed reading your into

    looking forward to some pictures as you get built up and start

    riding that MB THING
  10. fastboy9

    fastboy9 Member

    Hi welcome to the forum, good to see guys like you with a mechanical mind,
    good luck with your build and look forward to seeing some pics! :)