Rear tire and motor locked up

[ayo2001]

hello, i'm new to the motorized bicycle world and i'm having a bit of trouble with my 80cc engine (Chinese engine unfortunately) I was on my way back to my house when all of a sudden the bike comes to a complete stop and the back wheel locks up. I also saw smoke coming out of the cylinder . So i tried to pedal and get the engine running again but nothing happens and its really hard to pedal when i pop the clutch. I'm not sure if the engine is seized or what but i know its not the chain getting bunched up. I can still move the bike freely when i disengage the clutch but if i try to get the engine started up it doesn't do anything, it doesn't turn over ,no kind of noise , nothing. Any idea what the problem might be?

 

[crassius]

first, take out the spark plug & see if motor turns when you roll bike forward - if it does, then you might have nothing wrong except for a slipping clutch & the forum has info about adjusting cable & flower nut

if motor still doesn't turn, you'll need to open drive cover & clutch cover so you can see where turning stops when you roll the bike - many times you'll find a bad or missing woodruff key in one of the shafts when this happens

 

[ayo2001]

first, take out the spark plug & see if motor turns when you roll bike forward - if it does, then you might have nothing wrong except for a slipping clutch & the forum has info about adjusting cable & flower nut

if motor still doesn't turn, you'll need to open drive cover & clutch cover so you can see where turning stops when you roll the bike - many times you'll find a bad or missing woodruff key in one of the shafts when this happens

ok the bike still rolls freely when i'm holding in the clutch and i can ride it like a normal bike, its just when i let go of the clutch it locks up and i can't pedal at all , but i'll check the drive cover and clutch cover

 

[butre]

if it's not slipping clutch then it's time for a teardown.

 

[Deleted member 12676]

it seized

 

[ayo2001]

i found the problem, after a semi-break down of the engine, i found that my piston was stuck and i had to tap it a little to get it loose. turns out that i didn't have enough oil in it for it to be properly lubricated to run correctly so thats why the piston got jammed. Could anyone recommend a good oil to gas ratio i should use. I was using about 20:1 but maybe thats not enough

 

[crassius]

I'd say 20:1 is plenty if that's what you're mixing. 6 1/2 ounces to a gal?

Unless you tried to mix in the gas tank rather than in a can which could be well shaken, then lack of oil didn't cause the seize - I'd look for another reason, like maybe the piston or rings on backwards.

 

[ayo2001]

I'd say 20:1 is plenty if that's what you're mixing. 6 1/2 ounces to a gal?

Unless you tried to mix in the gas tank rather than in a can which could be well shaken, then lack of oil didn't cause the seize - I'd look for another reason, like maybe the piston or rings on backwards.

yes i did try to mix it in the gas tank, i'm not supposed to do that i take it?

 

[butre]

if you do the procedure is to fill with fuel a quarter way, dump in the oil, shake the bike, fill the rest of the way, shake again.

 

[crassius]

that can be risky - I've seen a lot of guys end up with almost straight gas that way or sometimes with the carb bowl full of straight oil - better to mix in a can and get it well mixed