Broken Crank?


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.

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


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.

Was the flywheel loose and causing bad vibrations? After installing a flywheel I always indicate it with a dial indicator.
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 know of three cranks that broke in same place. All are stock appearing or modified engines. All three still ran.
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 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
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