Engine Trouble Broken Crank where mag bolts onto

[Saddletramp]

One millionth of an inch is large for people that want it right. No one wants our 1100.00 motor. The $80 motor is better.

 

[sactownie]

May we hold back the sorrow, an $80 motor has bit the big one. Keep it for parts, all you can do.

So where do you get a motor for $80? Mine bit the dust after 3 weeks of casual riding, about 1 1/4 gallons. $80 shipped? This can get pretty expensive, I got about 110 miles out of that motor and I could have filled the tank in my gas hog little dakota for atleast one tank for $80 and got 200-250 miles.

 

[Fabian]

So fabian do you agree that crank broke where it broke could not have been caused from over revving the little motor?

I think it's highly unlikely that rpm induced structural failure happened in what would normally be an unloaded section of the crankshaft. Most likely is that the crankshaft suffered a flexing moment by foreign matter lodged in between the magnet and the magneto arms, which would have caused a massive torque spike; shearing the shaft in half, on the back face of the magnet.
I have never seen this kind of failure on any of the engines (at my local vendor) that have been returned, due to warranty claims, and i have been around these engines for approximately 4 years.

Typically over revving results in failure of the big end connecting rod bearing and/or the small end connecting rod bearing, and in some cases the crankshaft main bearings.
In extreme cases of over revving it results in failure of the connecting rod by material separation.

 

[sactownie]

One millionth of an inch is large for people that want it right. No one wants our 1100.00 motor. The $80 motor is better.

So where is the $80 Motor????? I paid $152 for the the one I got 3 weeks out of. I would love to find one for $80 shipped.

 

[sactownie]

I think it's highly unlikely that rpm induced structural failure happened in what would normally be an unloaded section of the crankshaft. Most likely is that the crankshaft suffered a flexing moment by foreign matter lodged in between the magnet and the magneto arms, which would have caused a massive torque spike; shearing the shaft in half, on the back face of the magnet.
I have never seen this kind of failure on any of the engines (at my local vendor) that have been returned, due to warranty claims, and i have been around these engines for approximately 4 years.

Typically over revving results in failure of the big end connecting rod bearing and/or the small end connecting rod bearing, and in some cases the crankshaft main bearings.
In extreme cases of over revving it results in failure of the connecting rod by material separation.

Thankyou, I am forwarding this message to her email, I know this wasnt my fault, I kept rpms low with the shift kit, the whole point of spending $200+ on that! I got unlucky, I found alot of metal bits and pieces attached to the magnet so I think your right, there was something in there that didnt belong. I checked it but I obviously didnt check it good enough as I didnt know what I was looking for.

 

[Fabian]

One millionth of an inch is large for people that want it right. No one wants our 1100.00 motor. The $80 motor is better.

I would be perfectly happy to pay $1,500 for a Chinese reproduction 2-stroke bicycle engine with an integrated shift kit; all machined out of billet and given a 120cc capacity with port timing set for maximum low rpm torque.

If someone manufactures it with "one millionth of an inch" tolerance, i'll buy it !!!

 

[Fabian]

I kept rpms low with the shift kit, the whole point of spending $200+ on that!

That's the exact reason why i purchased a Sick Bike Parts shift kit, and it's the main reason why the bottom end of my last engine lasted 10,000 kilometers (approx 6,000 miles) with top ends lasting an average of 4,000 kilometers (approx 2,500 miles).

I have installed a Rock Solid Engines reed valve intake to my Chinese 2-stroke bicycle engine which helps boost low and midrange torque; allowing me to keep the engine in it's torque sweet spot; between 3,500 rpm and 3,800 rpm.

 

[sactownie]

I would be perfectly happy to pay $1,500 for a Chinese reproduction 2-stroke bicycle engine with an integrated shift kit; all machined out of billet and given a 120cc capacity with port timing set for maximum low rpm torque.

If someone manufactures it with "one millionth of an inch" tolerance, i'll buy it !!!

No **** man, if its manufactured to japanese standards as with honda engines. Id buy it too, Id just worry about it getting stolen! Like really expensive stolen!

 

[sactownie]

That's the exact reason why i purchased a Sick Bike Parts shift kit, and it's the main reason why the bottom end of my last engine lasted 10,000 kilometers (approx 6,000 miles) with top ends lasting an average of 4,000 kilometers (approx 2,500 miles).

I have installed a Rock Solid Engines reed valve intake to my Chinese 2-stroke bicycle engine which helps boost low and midrange torque; allowing me to keep the engine in it's torque sweet spot; between 3,500 rpm and 3,800 rpm.

Yea I was revving the little motor to maybe 5,000 rpm and shifting, I was crusing 30mph at about 2500rpm when it happen. It seems to like 2500 rpm at 30mph when on flat level ground. These guys on this site getting 700 miles out of an engine are using 1 gear, 7 or 8,000 rpms at 30mph. This is why I am so disappointed in this motor, thought id get 3,000 miles not 110 miles!
The seller enginesonlineshop also charged me california sales tax so I didn't think anything of it at the time but then He sent me the fedx tracking number and it comes from the big desert state of nevada. Why is he charging 9.9% california state tax when he is in nevada, las vegas to be exact??????? He pocketed an extra $12 to be exact and I think thats against the law? collecting for taxes and not actually paying them????? I know subway sandwiches has been doing this for years on there sales of cold sandwiches that are not taxable. the owner just keeps the money as there pocket money......

 

[HeadSmess]

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!)