Trouble shooting the bicycle engine that won't start

deacon · Feb 21, 2008

So here is a chance for all of us new guys to trouble shoot an engine that just doesn't start. So it has sat for a couple of weeks and been moved from one bike to another but it should still be the same things.

The engine rotates but doesn't start. It appears to be dead. It has compression since it won't roll freely.

So what is the next thing to check and how do i go about it.

I have checked the simple things... There is gas in the line. I have wired the black and green wire twice since it had to be rewired. I have disconnected the kill switch

deacon · Feb 21, 2008

Re: Trouble shooting the engine that won't start

Okay I found mine in the wiring but, we still need this thread I think. What do you do first if one day your engine won't start.

paul · Feb 21, 2008

Re: Trouble shooting the engine that won't start

first think i do is cuss rotfl

then i check for good spark
then getting gas
these 2 things are usually gonna be the reason for not starting
then i go to wireing etc

deacon · Feb 21, 2008

Re: Trouble shooting the engine that won't start

Okay but in detail how do you verify each of them

deacon · Feb 21, 2008

Re: Trouble shooting the engine that won't start

I can see I'm gonna have to pull teeth... Okay suppose I couldn't get the engine to fire.

I check the fuel line and the fuel turn off switch and its okay.

So do I pull the spark plug to see if it's wet and smells of gasoline. Is that the easiest way to determine if there is gasoline getting to the cylinder.

So if the plug is wet go on if not check the carburator. (I tapped on the bottom of mine just in case the float was stuck by the way)

Bikeguy Joe · Feb 21, 2008

Re: Trouble shooting the engine that won't start

I have only ever had a problem with the crappy kill switches that come with the kits....buy a momentary switch at you favorite electronics store to replace it asap.

deacon · Feb 21, 2008

Re: Trouble shooting the engine that won't start

I use a toggle switch for an ignition type switch and kill. I expect you could use a key lock as well but the toggle works I hope for some kid trying to start it when I'm inside a store. I do sometimes not chain it down if I'm gonna be gone just a minute.

Norman · Feb 21, 2008

Re: Trouble shooting the engine that won't start

Not chaining it invites someone to take your bike a good chain and lock will slow down an honest thief.

deacon · Feb 21, 2008

Re: Trouble shooting the engine that won't start

I know i'm a bad daddy for my bike... Good to see you back how was the vacation...

deacon · Feb 22, 2008

Re: Trouble shooting the engine that won't start

Okay you got a wet stinky plug and its out of the head so now is the time to check the spark. Now I'm telling this from memory so don't be surprised if I get this wrong. Norman needs to tell it but he hasn't joined in yet so here goes.
take off the chain cover and get the rear wheel off the ground. with the plug wire near the head turn the engine over and look for a spark.

Now I think that is how he said to do it. I have never had to go that far yet.

I think that tells you that your electrical system is okay.

If you don't have spark, I would check out all the wiring. The kill switch, as well as the connections on the blue/green and the black ground from the engine magneto to the coil. There does not seem to be a lot to go wrong with the wiring, but I still managed to screw mine up.

I think if my plug was wet and stinky, and my spark was present I would think the spark plug itself was bad.

I have had cracked plugs in cars a few times so I wouldn't rule that out as many times as I have had to pull mine in this engine. I hope I don't have to pull it any more.

When I switched frames I installed the new plug and wire. It did seem to make the engine smoother but that is probably all in my head.

I'm sure if Norman weighs in he will improve this a lot.

bravofire84 · Feb 22, 2008

Re: Trouble shooting the engine that won't start

i know when i got my kit the cdi wire jus luckily happened to be connected to the unit but i connectedit and got spark. Jus sayin check the obvious i was lucky it could be fixed.

deacon · Feb 22, 2008

Re: Trouble shooting the engine that won't start

Mine fell out after a few miles so yeah check everything easy first. Always my first rule of repair. Save the hard stuff till everything else has be ruled out.

dgoria5 · Mar 18, 2008

after having fuel problems and wouldn't start so i disassembled the carb and put it back together. However now when i go to start it nothing happens at all, the wirring noise is not even present. does anyone know what this may be and how to fix it? I'm surprised that im getting so many problems out of a new motor. but hey it does'nt only happen with these chinese motors

deacon · Mar 18, 2008

I don't know if anyone else agrees but it seems to me when there is no whirring noise it is the ignition. No fire on the plug kind of thing. don't ask me why but that seems to always be the case with me. disconnect your kill switch and check the other wires. Your plug wire as well. Mine fell out once.

Bikeguy Joe · Mar 19, 2008

No whirring noise? Is the engine turning over, or is the clutch slipping?

When you drop the clutch, does it get really hard to pedal, but no sounds at all?
Or does it get really hard to pedal, and sound like an engine, but with no power?

dgoria5 · Mar 21, 2008

I Checked all the wiring and it seems to be fine. However when i took the spark plug out to see if there was any spark the motor did start to whirr. There was no spark. when i put the plug back in again no whirring noise. could it be a faulty plug? or is it something else llike the CDI or the magneto?

thatsdax · Mar 21, 2008

Check the magneto with a DVOM. Check between the blue and the black wire open or unplugged. Value should be around 253 ohms between those 2 wires. Thanks..

deacon · Mar 21, 2008

If you dont have a meter check to see if the wire itself will spark. It it does its the plug if not then it is likely the cdi or the magneto.

Bikeguy Joe · Mar 21, 2008

dgoria5 said:
I Checked all the wiring and it seems to be fine. However when i took the spark plug out to see if there was any spark the motor did start to whirr. There was no spark. when i put the plug back in again no whirring noise. could it be a faulty plug? or is it something else llike the CDI or the magneto?

.k., no whirring noise when you put the plug back? Sounds like the clutch is slipping and not turning the engine over.

Also, you said there was no spark. Did you have the plug grounded to the engine when you spun it over?

deacon · Mar 21, 2008

Joe has a good point the added compression might mean the clutch is slipping enough to not allow the engine with compression to turn over. That makes pretty good sense. But the no compression engine will turn over since it is easier on the clutch.

Trouble shooting the bicycle engine that won't start

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