Engine Trouble Broken Crank where mag bolts onto

[HeadSmess]

i got 5000 plus on a standard skyhawk 48.

single speed, with a pipe for 9000 rpm. and i keep it at WOT.


60km/h+ with a 28t rear on 20" rims. go do the maths yourself.


popped head once to have a look. popped pipe to clear out all the carbon. popped carb to clean out accumulation of gunk.

still running.


btw. detonation occurs at low rpm with high loads.

i come from the land of rev the stinking lil things and let them do the job properly, with only light loads.


chains and gears power ratings go UP with rpm. a pushy chain may snap if lugged around all day at low rpm, but will last for years with double the rpm.

go figure.

 

[HeadSmess]

and last final thought. the magneto may seem like a low stress area.


go look up electromagnetism.

find out how an electric absorber works.

that magneto, when running, can actually experience pretty large torque fluctuations.

combine that with a flaw in the steel due to lousy QC, and it will break.

bad luck.

put on your pants and tell the missus to zip it.

they respect that.

 

[sactownie]

honda, and many others, got OVER 100MPH from 50cc engines, circa 1960.

the record stands at 144 point something MPH. 50cc.

53 years ago roughly. shows how much we really have advanced, huh? the harrier jump jet was first flying in 1943, i believe. so its as old as my mum. we still ride on rubber things that revolve! thats 100 years old, at least...

dont ask for exact dates, im just hoping my memories right still i dont mind if someone corrects me on those points.


120cc is POINTLESS on a pushy. if the engine was made right, its like putting a cr125 on a pushy. it isnt going to happen. you may as well keep the rest of the cr125. they come with a factory rated output of 35 horsies!


30 cc, with a 3speed, auto shifting box. now that will do the job. 22:1, 18:1, and 12:1 approx. there is no need to do more than 60. (though i do try)


id also be installing some sort of handgrip hooked to the ignition coil security system. with a 30 second lag, of course, so it bites when theyre whizzing down the road at full tilt


or a flaming fuel tank, reminiscient of ROBOCOP! torch the thieving scoundrels!


(apparently its actually a real accessory in south africa!)

I hope you were replying to the wrong thread cause nothing you said makes any sense. I have had motorcycles and there ok, but I loved the 3 weeks I had with my motor bicycle. I actually had a major break down and was able to pedal it 3 1/2 miles back home, cant do that with a motorcycle! I would have been stuck for hours waiting t pay a tow truck $100

 

[sactownie]

and last final thought. the magneto may seem like a low stress area.


go look up electromagnetism.

find out how an electric absorber works.

that magneto, when running, can actually experience pretty large torque fluctuations.

combine that with a flaw in the steel due to lousy QC, and it will break.

bad luck.

put on your pants and tell the missus to zip it.

they respect that.

Well if I put on the pants any more I'm going to have to off her. I just wanted some proof that I didn't destroy the motor after 3 weeks myself!

 

[HeadSmess]

boarder collies are ...usually black and white but thats the general shape and look of one smart dogs.

a breeder would call that a crossbred mutt... even smarter!

good to see you got a sense of humor! dont go so far as to off the lady, old boy. end up becoming someones missus doing that...


my rant about other things was sort of based on the concept of a 120cc engine in a pushy...maybe it was the wrong thread...iunno now and all this whining about how the engines fall apart when revved over 2500 which is barely cracking idle, in my opinion... that gets my goat.

once again. i happily keep em WOT, over 7000rpm for sometimes an hour at a time. some die abruptly. they USUALLY last a long time.


g'luck i think i said earlier... stick the magnet to the fridge as a trophy if anything

 

[Fabian]

120cc is POINTLESS on a pushy.

That's your opinion, but it is not my opinion. My needs are for the engine to operate in a specific manner to suit my particular requirements.

 

[Fabian]

that magneto, when running, can actually experience pretty large torque fluctuations, combine that with a flaw in the steel due to lousy QC, and it will break.

Crankshaft materials failure from electromagnetic torque fluctuations are never going to happen on a Chinese 2-stroke bicycle engine,,,,, ever,,,,, even with poor quality steel !!!

 

[KihOshk]

I would probably end up TRYING to reconnect the post by tapping both ends, inserting a stud with RED LocTite, GENTLY adjust the mating so as to assure proper timing, and let it set overnight. You're better off though just buying a new flywheel-assembly...there's too much work involved, and too many degrees of freedom in my method. Also, be sure to demand satisfaction from the seller; shame them if need-be. I don't see how this damage could have been caused by negligence on your part.