The Motobecane

Discussion in 'Photos & Bicycle Builds' started by flashstar, Nov 16, 2009.

  1. flashstar

    flashstar Member

    I've had this bike since I was 13 and it was getting a bit too boring for me. The solution: put an engine on it! :helmet:

    Here are the "specs":

    Dax 70cc Engine kit
    B6HS NGK Plug
    Andy's Top Hat adapter with 40 tooth sprocket
    SBP Fuel filter
    SBP front engine mount kit


    I ran out today and the exhaust bent at the exhaust shop. I was charged $20 so that puts the total parts cost somewhere in the range of $250. I spent the greater part of today breaking in the motor. After 3 cycles, the engine is already starting to pick up power! I still have a couple problems though. The gas tank is leaking a bit from the connection between the tank and fuel shut off valve. I ran into town and picked up some thread sealant so that problem should be fixed some time this week. I'm also waiting for the chain to stop stretching so that I can throw out this evil tensioner.

    Another issue is that the carb needs to be tuned. I believe that it's running very rich as the engine seems to be 4 stroking much of the time.

    So far, I have gotten a ton of "that" looks (one from a spandex woman biker), thumbs up from a bunch of little kids, and one person complimented me on the build so you guys were right about the public reception. :D

    Thanks for all of the help on this forum. I wouldn't have been able to do this build without it. :tank:

    Attached Files:

    Last edited: Nov 16, 2009

  2. roughrider504

    roughrider504 Member

    Nice build.

    Your carb is probably set up fine, it is normal for 2 strokes to 4 stroke under little load. My 66cc 4 strokes a lot because I am using only a portion of it's potential power most of the time. Under acceleration and wot it should 2 stroke though.
  3. flashstar

    flashstar Member

    Thanks for the information. I pulled my plug and saw that it was wet and black with oil so I moved my e-clip up one notch. Right now it 4 strokes unless I am accelerating quickly or going up hills which is I guess what it should be doing. I'd rather be on the rich side than the lean side.

    I have been having another problem recently too. When I'm cruising, the gas stops flowing from my gas tank until I take the gas cap off. I'm guessing that my cap isn't venting properly. Should I just get another cap?
  4. wheelbender6

    wheelbender6 Well-Known Member

    The chrome tank nicely matches the lettering on the frame.
    I don't think the cap provides any venting. Venting is normally
    provided by small holes in the filler neck.
  5. retromike3

    retromike3 Member


    the gas tank looks like my new one,except mines not crome and I would not worry about venting quit yet I remember standing my bike up on one wheel with my new gas tank and having it leak gas on the bike and me.

    Mike Frye- the bike guy:D
  6. Slackbiker

    Slackbiker Member

    That is also amusing "Moto-becane". of course.
  7. retromike3

    retromike3 Member


    I used to sell that brand of bike in the first "real" bike shop I worked in. I used to refer to them as moto-beercans.:grin5:

    Pretty good bikes on average but quite a few came with the horrible Simplex derailleurs. Plus at the time they did not use the standard size tube diameters. Being french, they also had French treaded components. Now Their probably made in China like everybody else. and English threaded.

    Mike Frye-the bike guy
  8. dchevygod

    dchevygod Member

    Nice build on a Motobecane 400ht. Too bad it was just another china girl motor but hey, rome wasn't built in a day. Soon my Goped adapted 460 will be the standard. In 10 yrs or so lol.