Broken Crank?

T

TedD

New member
Can someone provide some insight as to what would cause a crank to break at the rod journal on the flywheel side of the engine? And, is this a common occurrence for clones? I had just installed a 6619 flywheel and had about 30 laps after the flywheel swap before it let go. Engine is Box Stock with 6619 flywheel and holy moses carb.

Here is a pic, sorry for the quality, was taken from my cell phone.
http://www.chonda16.com/images/BrokeCrank.JPG

Thanks,
Ted
 
Looking at the picture a crack appears to have started on the left side of the crank in photo.

Why?

Defect maybe.
Could have been dropped on a concrete floor in China at just the right angle to start something.
Bad heat treating not allowed to cool properly.
Bad forging or machining mistakes caused a high stress area.
Hard to say.

Stuff happens.
 
Must have been a defect like winstonsmith said. No way a properly assembled BSP engine makes enough force to break a nondefective crank.
 
Was the flywheel loose and causing bad vibrations? After installing a flywheel I always indicate it with a dial indicator.
 
Flywheel was good and tight. No slippage either as I installed it with the key and the key was intact when I removed the flywheel. I also had to use the flywheel puller to remove the flywheel.

swamprat said:
Was the flywheel loose and causing bad vibrations? After installing a flywheel I always indicate it with a dial indicator.
Click to expand...
 
Same thing and same place happened to mine. I think just a flaw. we never turn them over 5900, just had to buy a new one.
 
I have broke cranks on several before..... this may become a issue especially on bull ring tracks.......but anyways what has happened to me in the past is my cart was bottoming out in the corner and this puts a unbelievable load on a crank..... not saying for sure but it may be a possibility
 
seen this on lots of motors poor quality cast crankshaft going to see more of this as the power increases over time.
 
Morning guys; Please take a look at this Guide and it may help you determine the "root" cause of your and any other failures take note of the Beachmarks and other indications http://www2.dana.com/pdf/AXSM0020. or spicer failure analysis guide. paste it in browser You will get many answers. I realize this is a Drive Line Failure Analysis guide BUT Broken metal is Broken Metal.................check it out you may learn something
Dave
 
I have seen broken cranks on engines that have bottomed out the rear gear also. It was happening at a temporary track regularly kart were dropping a wheel off the pavement, breaking the end off the crank.
 
We are running some highly modified clone engines and have broken 5 crankshafts in the last few months. Each of them were various clone versions. I wonder if a genuine Honda crank would be any tougher?
 
it is just another quality piece from China . they are cheap and not meant for what we ask of them . so pick up some new parts rebuild it and get back on the track
 
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