busted flywheel/sheared shaft with pics

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Spunout

Spunout

MB Builder Extraordinaire
Jul 21, 2008
475
2
0
coventry, RI
blog.360.yahoo.com
tooling down the road at 40mph, i felt the slightest drop in speed just before the motor died."huh?" i noticed black oil coming from one of the bolt holes on the bottom of magneto cover.
pulled it off and there was the flywheel, wedged into the magneto.
the flywheel is comprised of three parts. apparently, one of them came off the main center. the shaft wanted to keep spinning and it did. sheared the flywheel right off.
gonna have to use the ez-out and replace the shaft/flywheel. if this wasnt my race motor, i probably wouldnt try so hard to save it.
 

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Forbisher

Forbisher

New Member
Dec 28, 2008
119
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Orange County, CA.
40mph? What size rear sprocket are you running?
Shifter kit?

Flywheel???? It is just a magnet not a flywheel

and you have sheared the shaft off that is pressed into your crankshaft flywheel

Ez out??? You need to split the cases and replace the whole crankshaft assembly

You would have to get one from a used engine

Might as well use a whole new bottom end or a new engine

Spunout said:
tooling down the road at 40mph, i felt the slightest drop in speed just before the motor died."huh?" i noticed black oil coming from one of the bolt holes on the bottom of magneto cover.
pulled it off and there was the flywheel, wedged into the magneto.
the flywheel is comprised of three parts. apparently, one of them came off the main center. the shaft wanted to keep spinning and it did. sheared the flywheel right off.
gonna have to use the ez-out and replace the shaft/flywheel. if this wasnt my race motor, i probably wouldnt try so hard to save it.
Click to expand...
 
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Forbisher

Forbisher

New Member
Dec 28, 2008
119
1
0
Orange County, CA.
dvddtz said:
I found this crank as a spare,just a couple of keystrokes. Motorized Bicycle Engine Kits. usflg All the parts are out there, you just have to look a little. Good luck. David
Click to expand...
Thanks for the link but....
Crank assembly includes: Right and Left sides of Crank, Connecting shaft, lower needle bearing and rod. Unit comes fully assembled. Used in both 48cc and 80cc generation 2 motors.
Click to expand...
There is no way that crank and rod will fit a 48 and a so called 80 and
what motor factory???

Also the bearing sizes, shaft diameters, keyways vary from factory to factory
so good luck!
The magneto side is probably the same but the crank gear side isn't

As far as I know Grubee does not sell replacement cranks
 
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2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Spun,
You're gonna need a new motor...........and I'd sure like to have that crankshaft seal if you're gonna trash that case. :)
Tom
 
Norman

Norman

LORD VADER Moderator
Jan 16, 2008
2,606
7
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71
pampa texas
2Door
I don't think you want that crank seal look at the oily poo there its been leaking I think. I do not think the leaking seal caused the mag rotor shaft to break but it looks like the seal was leaking.
Norman
 
Spunout

Spunout

MB Builder Extraordinaire
Jul 21, 2008
475
2
0
coventry, RI
blog.360.yahoo.com
Forbisher said:
40mph? What size rear sprocket are you running?
Shifter kit?

Flywheel???? It is just a magnet not a flywheel

and you have sheared the shaft off that is pressed into your crankshaft flywheel

Ez out??? You need to split the cases and replace the whole crankshaft assembly

You would have to get one from a used engine

Might as well use a whole new bottom end or a new engine
Click to expand...

the motor has been ported, handmade intake and large carb from a XR80. running a 36tooth, and top speed is 44mph. thats fast.

i always called the magnet a flywheel...dunno why.

oh man, i dont have time to split the case. i thought the shaft screwed in, not pressed. ive never messed with the bottom ends much, just the tops. never needed to.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Norman said:
2Door
I don't think you want that crank seal look at the oily poo there its been leaking I think. I do not think the leaking seal caused the mag rotor shaft to break but it looks like the seal was leaking.
Norman
Click to expand...
Norm,
You're right. I posted that before we found those other ones. I should get those this week. I'll let you know if they fit.
Tom
 
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