To cushion or not to cushion...

Discussion in 'General Questions' started by RedBaronX, Aug 1, 2010.

  1. RedBaronX

    RedBaronX Member

    after gathering and prepping pieces, I will be FINALLY assembling my first MB this week...

    I know that VIBRATION is the enemy of the MB... now, the logic tells me that rubber padding where the mounts attach to the frame would reduce the vibrations of the motor, but I could have sworn I just saw somewhere on the forum yesterday that padding where the motor mounts to the frame can actually exaggerate the vibrations (and I can't find where I saw it)

    I have already bought some gasket rubber in sheets-- it's strong, it's dense-- with the intention of using it for the mounts, but maybe that is NOT the way to go.

    I already have THIS page bookmarked, about mounting at the right angle:

    I'm going to be riding hard, and I want to get this right... Experience? Opinions?

  2. retromike3

    retromike3 Member

    Don't do what I did.

    I had a similar notion when I put my first kit together and what I did was to drill a hole in my seat tube and down tube. (I made the mistake of following the directions that I down loaded from Boy Go Fast) Next I put a rubber grommet between the down tube and the motor.

    Everything was fine for about a week and then I felt a big change in the vibration and when I got off the bike it looked like somebody took a hacksaw to the seat tube. I am sure that not mounting the down tube was a contributing factor. Now with a new motor( a zipp cycle) and a new frame(Giant 20" 1990 something) that I acutely welded the rear bracket on, it is a lot more stable. It still has problems when the motor gets to a certain range but I can live with it. (rode it this morning, felt grate!)

    I had to weld a bracket to the seat tube because when I added a Sick Bike Parts tuned pipe and a thinner head gasket it effectively doubled my power, thus making my old brackets slip, so the chain got loose, then it jumped off the sprocket, wrapped around the hub and broke about eight spokes (can you say,walking home a half a mile dragging my rear wheel mad as ****).:shout:

    I also broke my motor mounts until I replaced them with grade 8 bolts. My suggestion would be to get a hardware kit from Sick Bike Parts and replace all of the cheep pot metal bolts that came with the kit. It will save you a lot of pain in the long run.

    I think that unless you can make a isolated motor cage to hold the motor in place it will be very hard to get any kind of effective damping without serious side effects. I would look more into balancing the engine which may be more work than what your willing to do.

  3. motorpsycho

    motorpsycho Active Member

    man, i have never had a problem with vibrations on either of my bikes.
    my engines are mounted to the frames with the stock hardware, and i just put thin peices of rubber in the mounts around the frame tubes.
    no vibrations here, no motors shifting, no loosening chains, or anything like that.
    i don't understand why so many people have vibration issues, i have never experienced it, and i have built 3 m.b.'s. (2 bikes are mine, and one bike is my friends) 2 with 80 c.c. 2 strokes, and one with a 50 c.c. 2 stroke. we got all 3 engines from the same place, and they are essentially the same design with a few small differences on the 50 c.c.
    one of my engines is in a 20" frame (the 50 c.c.), another one of my engines is in an o.c.c. chopper frame (80 c.c. using "barry's mount" with a few slight modifications), and my friends is in a 24" frame.
    Last edited: Aug 2, 2010
  4. RedBaronX

    RedBaronX Member

    well that's the thing... the gasket rubber I bought was cheap, it's hardcore dense and tough... and it's such a simple fix...

    and because it IS so simple, but it doesn't seem like a lot of people are doing it, maybe it ISN'T the right thing to do...
  5. retromike3

    retromike3 Member

    engine shifting

    The main problems I have had was when I souped up my motor. I don't remember having the same problems when I was using just the stock engine.

    There does seem to have a certain range when the motor vibrates more than usual. I think it has more to do with the fact that the engine is a single piston set-up than any other reason. Its very possible that you can change ratio of the vibration with a little rubber in the right place.