4-stroke 49cc cent Clutch Removal help?

Discussion in '4-Stroke Engines' started by KCvale, Mar 13, 2013.

  1. KCvale

    KCvale Motorized Bicycle Vendor

    I won't go into the plethora of screw-ups this rookie builder made on this direct drive 49cc build before he brought it to me to re-build but I am stuck on the last of his screw ups and could use some advice to get this nightmare out of the shop!

    I certainly don't know why but can't even see how he managed to put a key between the bell housing of the cent clutch and motor shaft but I can't get to the back off it to pry it loose without risking the motor case and I can't grab it with anything so the cent clutch bell actually freewheels and not fixed to the shaft.


    Heat seems like an option but I don't want to risk the motor seals and the key is wedged in there sideways pretty good.
    Is trying to drill it out the only option?

    I won't go into everything else he did back-ass backwards but it will eventually serve as an example of how to everything wrong trying to improve with no concept of basic mechanical function.

    Thanks guys.

  2. Purple Haze

    Purple Haze Active Member

    Here's an idea; have you ever used a steering wheel puller? You'll have to drill and tap 2 holes 180 degrees across from each other, then it should pull right off. If you drill in the right places, it shouldn't affect strength or balance. You have my sympathies, I hate fixing other peoples screwups!
  3. Samdallas214

    Samdallas214 Member


    Some tips.

    I have also drilled a hole in the key and screwed in a metal screw with the biggest head I could find and then used a pry bar on the screw to remove it .
    Some times clamping a pair of vice grips on the screw turning the engine up side down can help, and hitting the vice grips with a hammer . has also worked . good luck.

    if the flywheel is going to be replaced I have even sawed the flywheel in front/back of the key and removed them that way, this I do as a last resort
    Last edited: Mar 13, 2013
  4. KCvale

    KCvale Motorized Bicycle Vendor

    Thanks for the tips.

    I don't have a steering wheel puller but I get the idea of how it works.
    I'll just try drilling the key out and beat on until it comes out and hope I don't damage the bell, this guy is already into me for what he paid for motor kit so I am trying to minimize his total loss for doing it himself in every possible way wrong.

    For example he replaced the Huffy back axle hub with a fixxe, put a band brake and freewheel sprocket on the drive sprocket, and a fixed sprocket on the pedal side, then tried putting bearings on the BB cups meant for a sealed bearing cartridge so the pedal shaft flopped around and destroyed both, and believe it or not it goes on.
  5. darwin

    darwin Well-Known Member

    Is there a space between that gear and the plate with the holes in it? Seems if there is you can have someone hold that gear and use a brass/copper punch to tap/hit on the crank.........is there any room between that plate with the holes in it and the housing? Was thinking maybe you could use a wedge on one side ever so slightly then work your way around from the other side. Wish I could see a side pic of that.
    Last edited: Mar 15, 2013
  6. zwebx

    zwebx Member

    if you do not have a puller, and you donty need the gear.... then go ahead drill 4 holes and tap them and tighten them up and keep the gear straight, eg making itself a puller
  7. KCvale

    KCvale Motorized Bicycle Vendor

    I got it apart!

    I thought I could pull the case cover off so I could get behind the bell and after taking out the 6 outer facing bolts I found there is a 7th bolt at the bottom coming in the other way from under the motor.

    I already pulled the motor and remounted it once so forget that, I got a bigger drill bit and went at the key itself again.

    Once I was in enough it was just a matter of turning the bell free on the shaft.
    The way the motor is under the top bar of the bike I was able to use a small socket extension and put it straight up between the top of the piston and the bottom of the bike frame.

    Then I took a pipe wrench that fit right in the gear teeth almost as if they were the same and gave it a turn.

    The bell moved, but the keyway didn't.
    Turns out there is a collared bushing between the bell and the motor shaft.

    This was my 'Ahh, Haa' moment in what he was thinking...
    With a rear freewheel drive sprocket and a clutch in the transfer case, there is no need for a cent clutch so key it to the shaft.

    The flaw in the plan is the stage 3 transfer cases don't have a clutch, it has direct gear PTO that engages when you pull it's lever abruptly and meant to only be used with no spin.

    The whole purpose of that PTO is to allow you rev the motor in place after the cent clutch kicks in.
    With no cent clutch the bell is always driving the gears.

    The coupling took the brunt of the damage as it is was the wrong busing anyway with a keyway, it needs to be a new free spinning bushing anyway.


    Ideally there would be a bearing insert that size opposed to a bushing so you would virtually no drag at idle as the bell set in place but I'll fint the bushing and grease it up well.

    The shaft did take some damage, the keyway grove was widened some.


    I went a little deep drilling so for future reference put your tape mark on your drill bit at 20mm, that is the width of that keyed bushing.

    When I get the key for the clutch I'll put some JB wend in the little grove left on the left side of the shaft, but there is enough already to work especially considering it a CCW spin from that pic so the 'sheer force' is applied to the non-compromised leading drive shaft slot edge.

    Anyway that is how I did it and the sucker is finally off with no real damage except to the least expensive wrong part anyway ;-}