Whirrs before firing..



my motoredbike is going into disrepair :(
it used to start up and run like a champ, and i've put maybe around 500 miles on it, with proper fuel/oil mixes, cleaning it at regular intervals or whenever it needed it, and doing pretty much anything to keep it in as nice of shape as i can.

but now when i dump the clutch to start it, the engine does kick in, but it's only a whir, i don't think there's any combustion. it takes about 4 minutes of pedaling at (at least) 10 mph until it'll really kick into life and the engine will fire. what's going on?

everything accessible prior to major disassembly looks good, i can't see anything wrong with it, and i don't want to rip the block apart until i absolutely need to.
does anybody recognize this or have any idea of what i could do?

thanks for any help
One of my engines behaved like that....Turns out it was an improperly set up carb (the needle with the little E-Clip on it was not letting enough fuel in on a cold start) in your case tho since it ran fine before I would suspect a fuel problem based....maybe gunk in the carb not letting enough fuel in on a cold start?....Will your engine choke off (use the choke as a means to shut off the engine) after warming up?....If not it may be that it is running lean and that would explain the difficult starting when cold.
hrm i have the same problem but mine is brand new. what would be the best way to adjust the carb?
sounds like head gasket ,, did you try tighten head bolts ,they all need to be tighten after the first few miles ,,i take it that you are running a happy time motor ,

some member said here on this forum ,, and i thought it was great advice,, when looking for help you should alway say ,how much experience you have around small motors ,, this really helps some of the top mechanic in their reply ,

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I have the same problem and my motor is new too however it was running fine yesterday. what should i do?
hey dgoria5,

I had this issue, and when the bike was at rest, let out the clutch and gently roll the bike forward, if the back wheel didn't grab, then its the clutch adjustment.
Don't do this too much as I've been told it can shear a pin in the motor.

I tried for ages to start/fix my bike with a clutch that was not properly engaging the motor. I found the solution by just pulling the clutch arm (where it attaches to the cable), then the motor engage and coughed, whereas it would usually "whirr".

They say these motors are sooo simple, well so are the things that cause em not to start.

Don't give up, eventually you'll work it out.
Most important, search on here, lotsa info for free...