Engine Trouble Running great until...

[Mr. Beaver]

Hello everyone... I'm completely new here, both to the site and to motorized bicycles. I have been riding bikes since i was young and now im almost thirty but never even knew you could put a motor on...

So here's the story... sorry if its long winded! Been ubering and taxing alot lately and decided to buy a bicycle (last one got stolen last fall), showed up to walmart and there was a gentleman out front selling two different motorized bikes... my heart skipped more than a few beats taking it round the parking lot... bought the cheaper of the two for 120$.

Took her home, filled up my jerry can with gas and oil as the gentleman had instructed and rode my heart out (to the discontent of my wife )... now i had been riding this bike for about three or four days for a couple hours each day with no problems other than a sticky throttle, which the gentleman had showed me how to fix (release throttle cable attachment @ carb and re-insert). i went out to a burger shop for lunch, came back to work and locked her up.

Now comes the trouble.... after maybe three hours after lunch i came out side and tried to get her started... its not pull start u gotta get up idk 5k/hour to engage the clutch and go... thought she was cold (canadian weather EH?) so i played with the choke a bit and while she would run with the clutch out there was no power... no umph, and if i pulled the clutch in she dies... so i get home call the gentleman and he says ill be right over!

that was two days ago, we have drained the fuel, put new stuff in... he took apart the carb, cleaned it and put it back, bought a brand new spark plug, installed it... still no difference... tried running with no exhaust... nope, disconnected the kill switch... nope.... loosened and tightened the clutch... nope ... changed the idle setting... nope

at the end of the day the motor runs but its not giving anything to the wheels, and if i pull the clutch she dies... now if i peddle like im Usain Bolt on steroids... she starts to puff and kick like shes about to rocket out the gate but a few seconds later its gone... im so heartbroken... i dont really wanna fully rebuild the engine as im sure ill mess it up... any ideas what the issue could be?

- new motorized guy with a broken soul

 

[crassius]

you mention "puff"

if it seems to be smoking a LOT when it does start, then I'd guess the fuel was left turned on while parked and motor is full

 

[Frankenstein]

Did you try checking for an air leak. Taking the exhaust should have changed something, if it didn't then maybe you already have an air leak elsewhere.. Though it could be the air filter is clogged if you didn't try riding without it.

Maybe none of the above? Is the magnet loose on the crankshaft? Kind of reminds me of timing being just a hair off. Always possible the cleaning was insufficient, removing the jet and cleaning it out with a thin needle or wire is needed.

120 is unusually cheap for a bicycle with a new motor, I'm guessing used? Maybe on its way out or just coincidently something internal failed after you got it. Also might be a good idea to get a plug reading, if it's black too rich or other problem, white too lean probably air leak. For all you know it was already running lean when you got it but you and possibly him just didn't know what it is, and so thought all was well and the motor died of heart failure, or is on the brink of it I should say.

 

[Mr. Beaver]

yes that did happen, i left the fuel switch in the on position while i parked it... wasnt until i came across these forums that i learned i should shut it off... if the motor is full how do i fix it?

 

[Frankenstein]

Ah OK, so the great mechanic you found didn't even bother to pull the plug out and pedal the bike around for a half block or so and determine if it was just full.. I see..

After a little exercise put the plug back in, torqued correctly, and try starting it again.

 

[Mr. Beaver]

OK, so i determined the wrench i have at home will not fit the spark plug by like 1/16-1/8 of an inch... so i cut the fuel off and attempted to ride her dry, burning off whatever is possibly inside... rode for about twenty minutes or so, turned the fuel back on and still nothing... the engine turn but doesnt fully kick, almost like im pushing the engine over... it wants to though... itll kick in for half a second on and off if im pedalling like there were bombs going off behind me... its odd its almost like it wants to start hauling but its like me on a sunday... doesnt wanna get outta bed... that little moment of power is so taunting tho its like... ah you almost had me...
so im sweating like a beast now and shes still licking her wounds... any other ideas? (fyi i will bring home more tools from work tommorow to pull the plug and try it that way...) but i gotta get to work tommorow and i dont feel like going back to uber

 

[Mr. Beaver]

ok update... gentleman thought it was the magneto or the spark plug.... replaced both... nothing... took out the plug and rode it as frankenstein suggested... rode for about two blocks... put plug back in and turned on fuel... still nothing... however we determined the engine is not actually firing... sounds exactly the same with or without plug in.... meaning the noises from the other day were the engine beginning to turn over... he has gone to go get a new carb and try that... any other ideas/suggestions?

 

[crassius]

did you check that head is on tight? - if no compression gauge available, look for oil seepage around where head attaches to cylinder

 

[Mr. Beaver]

ok so yeah, i made sure the head was on tight, and there doesnt appear to be any oil leakage there.... decided when i got home from work today to give her another shot... and she coughed and spurted and then ran like the breeze for about an hour.... went to the store... and on the way back she started to cough and sputter again... im so confused its like this motor has a mind of its own... pls help

 

[crassius]

could be some crap blocking fuel filter over time, but did you check that after an hour you still had fuel in tank?