Trouble shooting the bicycle engine that won't start

GoldenMotor.com

Jmichaelg21

New Member
Sep 18, 2015
7
0
0
chicago
Ok so heres the story i just had my first build worked great for 2 weeks died turned out to be the magneto so i replaced it ran great for another week and its dead in the water again so first thing i did was check for spark heres where it gets tricky ive spent all day tinkering with it even splices my wires directly and when i turn the engine over she sparks a couple of times then nothing rode her just yesterday and she rode great parked it over night after putting a pin in my pedal so it doesnt come out and accidentally left the fule petcock open got up this morning to go to work gas on the floor and she wouldnt start could me leaving the petcock open have anything to do with her not starting anyways so i try to ride it down the street she somewhat starts but bogs down and dies like i said i get a spark and then it stops what is wrong with it? Please help!!!!
 

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
I'd guess your motor is full of fuel. If you can start it, feather the throttle up & down to keep it running for a few minutes and it will clear on its own (you'll see LOTS of smoke at the muffler). If you can't start it, then take out the plug and pedal around with clutch engaged to pump all the fuel out the plug hole (keep spark plug & wire away from that area while doing this).
 

Jmichaelg21

New Member
Sep 18, 2015
7
0
0
chicago
What about the spark plug it sparks then stops adjust gap same thing sparks then stops i even went to the efforts of taking the spark plug wire and cutting like 1/8 of an inch off both ends still the same
 

Graham1973

New Member
Sep 6, 2018
3
0
1
50
Hi all I've just bought one of these Chinese engines and installed it to bike, got compression fuel and spark but just won't fire up any help would be great
 

javy mcdees

Active Member
Jul 30, 2018
143
59
28
52
Hi all I've just bought one of these Chinese engines and installed it to bike, got compression fuel and spark but just won't fire up any help would be great
make sure the magneto is properly set. it could spark but still wont fire up. use the business card to center up the magneto.
 

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
after turning motor over a lot, I take out plug to check for spark and to see if plug is wet with fuel

if both are there, next check is with compression gauge - anything better than 120 or so is good - note, before doing this test, I listen to hear if carb slide clicks as it hits bottom when throttle is closed
 

Graham1973

New Member
Sep 6, 2018
3
0
1
50
after turning motor over a lot, I take out plug to check for spark and to see if plug is wet with fuel

if both are there, next check is with compression gauge - anything better than 120 or so is good - note, before doing this test, I listen to hear if carb slide clicks as it hits bottom when throttle is closed
Cant hear nothing with carb
 

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
make sure carb is assembled right and cable has enough slack - when slide not all the way down, these are harder to start
 

Citi-sporter

Active Member
Jun 16, 2014
206
43
28
North Bend, Or,
Is your spark plug gapped at about 0.020" to 0.025"?

Did you buy a better plug like an NGK B6HS?

After getting the plug wet with fuel: did you pedal your bike around with the clutch engaged?

the plug out but grounded to the engine case so to not ignite the fumes?

Can you see and hear the spark? It should be bright blue and make a tiny, but audible snap noise when fired.

Don't attempt to start these engines with the plug pulled but not grounded so as to not damage the CDI by killing it with open voltage feedback.