bike or motor shakes shaking at mid to high speed

Discussion in 'General Questions' started by double trouble, May 24, 2012.

  1. My newest acquisition is a sears free spirit with a longdu flying dragon. The bike was another $130 purchase that really is a pretty good setup. I had to remove the motor mounts , turn the lower one facing up and put thin rubber around them because bike shook pretty hard. It did help some ,but....
    The bike is decently smooth up until about mid throttle at about 15 mph. Then the bike shakes pretty bad. Here are some of the problems . I just need to know which I should fix first and how.
    The motor is turned slightly right , which affects the geometry of the chain, tensioner, and sprocket. It makes a whirring sound like the chain is hitting inside the clutch cover. It was even worst before I raised the motor an inch and put the rubber in.
    Both wheels are a bit warped and the bearing are a touch loose.
    I believe the motor itself is doing the shaking too and need to know if there is some simple fixes to try.
    Overall the bike has been pretty reliable in the first 20 miles I put on it.
    The carburetor is a piece of **** and adjusting the idle never seems to hold steady , but I have seen this before. I did get it pretty decent the last 2 trips. It also likes to stay at higher revs when you come to a stop. Probably time for a new carb , even though this one probably only has 50 miles on it.
    Is there any adjustments I can make. I pulled the slide out and teflon lubed it.
    The clutch cover has mismatched screws from some that were lost. What size are they?
    The spark plug wire is original . That will go bye bye soon.
    I am looking for another bike to put this motor on because it seems to have a lot of power. The angle head motors seem to pull harder.
    How do you knowtell what cc this motor is. Is it stud size or can I measure between the bolts.
    Sorry to be so long winded , but I really like these bikes and fixing them is fun.

  2. Lunardog

    Lunardog Member

    Well Ill tell you this first , I am a newbie myself. However, General mechanics are not foreign to me so I can say with some degree of confidence. You are going to get hurt!! The list of issues with your bike make it a seriously unsafe piece of machinery and I urge you to back up and make some needed repairs before you get injured. If you have the motor direct drive to a ragjoint sprocket and your motor is misaligned, guess what happens if your chain jams up at the engine doing 20mph. Pray the chain breaks because if it doesnt your rear wheel locks up and your potentally out of control and who knows where you will end up.(in the road in front of a car or truck, in a ditch or worse??) Then go in to the warped wheels, self explanitory. If they cant be properly trued adjusting spokes they should be replaced. Faster you go the more they are going to wobble and cause you shakes,wobbles,vibrations????? Lastly , loose bearings???? I dont intend to sound like an over protective parent here but I also prefer not to see a fellow MB'er splattered all over the road over a $15 or $20 part. I urge you make some needed repairs before you continue riding. Bringing the bike back to base safe functionality may also fix some of the issues you came here inquiring about. Take care.
  3. BigBlue

    BigBlue Active Member

    Ditto everything Lunardog said. If the engine won't fit the frame, get another bike. If you do get the engine to properly fit the frame, take the bike to a LBS for tune-up and fix the known problems if you can't do the repairs yourself. I would also check the headset for looseness and check the frame for cracks or looseness of the lugs. I think those Free Spirit bikes had lugs?

    Good Luck,

    AKA: BigBlue
  4. somewhat better

    I spent a couple hours doing some of the repairs. Remember that most of the issues I stated were not major except the engine position.

    1 trued the front wheel, removed the bearings and greased.
    2 tightened the back wheel bearings a bit
    3 re-positioned the motor several times. The tensioner position was keeping it from being straight.
    4 adjusted the brakes
    5 moved the tensioner several until I was satisfied
    6 tightened the head, carb, and exhaust bolts

    Went on many test rides down the cul-de-sac. One ride the spark plug blew out. Put a china cheapie back in. I still have a problem where the engine revs up to full throttle , then feels like it wants to quit and the revs go down.
    I hope a new plug and wire will solve this.

    Most of the vibration is gone , but not all. I still have a high pitch grinding or whining noise when I let off the throttle. Not sure if it is chain , clutch sprocket , or something else.
  5. mmachine

    mmachine Member

    I had a bad vibration till I realigned the rear sprocket, it must be perfectly
  6. Cavi Mike

    Cavi Mike Member

    Between the terrible vibration and the slant head, it sounds like a 66cc. They're horribly balanced. Isolating the vibration is almost impossible, typically you just end up changing at which RPM the vibration shakes the whole bike.

    As far as adjusting the carb, there are far too many things to list and I doubt I could even remember all of them in one shot. Search the forums but if you like to tinker as much as you say you do, just keep tinkering, you'll find all of its faults soon enough.
  7. more troubles

    This time I took it for a ride and broke down. Either the rear wheel came loose or the back engine mount stud backed out from vibration. Luckily I had some tools with me. I pulled the back tire and,took the chain off and limped it home.
    It felt like the motor was locked up . After I got it home , I think I found some of the problems. The chain sprocket cover only has 2 screws. Its probably rubbing because this motor has a really small area where the chain lies. My other bike , the chain can come off over the small sprocket , but not this one.
    I went to a nut and bolt store and got 2 hardened hex screws for the back mount.
    Come to find out that I snapped off a engine mount stud pretty much flush with the block . Oh fun, I guess its time to drill and hopefully get and EZ-out in there.
    So instead of working on it, I had to fix my riding mower. I blew a head gasket on my 16 hp intek a week ago. I guess mowing the grass comes first.
    I'll fix the bike this weekend.