Pocketbike Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
I've acquired 2 49cc mini choppers one runs good the other I'm getting frustrated with. I've replaced the carb, spark plug (BM6A), fuel lines and filter. I checked for spark and I'm getting a nice bright blue spark I also checked for compression on the cylinder and its got compression and it still wont start. Any advise would be appreciated I'm not sure on the brand name but here is a picture of them.

 

·
Banned
Joined
·
24,164 Posts
Try to start it a few times and pull the spark plug, is it wet??, what color is it. Then put a little gas down the plug hole, put it back and try to start it. On a 2 stroke, the plug can get fouled real easy.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Try to start it a few times and pull the spark plug, is it wet??, what color is it. Then put a little gas down the plug hole, put it back and try to start it. On a 2 stroke, the plug can get fouled real easy.
The plug is wet. Seem to be clean. I put some gas down the chamber pulled it a few times and still wont start.
 

·
Registered
Joined
·
489 Posts
I got one of those spark plug cable checkers, to find the one that is foul on automobile engines. You place it between the spark plug and the spark plug cable, crank and see if it lights up.

- cable
- plug

There are two small cables that come out from the side of the flywheel near the spark plug cable. On the mini chopper I got, I simply cut the cable and installed a switch.


Good luck!
 

·
Registered
Joined
·
5 Posts
Discussion Starter #6
The killswitch on the bike is a key. I know that works because when I
Turn it to the off position I get no sparK and when I turn to the on position I get spark. I tested the spark by holding the plug against the engine. The wiring harness is very similar to the one on my X2 pocket bike. I had it started for 10 seconds after I pulled it 100 times and that was it. Messed around with the idle screw and throttle for an hour and still nothing.
 

·
Banned
Joined
·
21,744 Posts
The killswitch on the bike is a key. I know that works because when I
Turn it to the off position I get no sparK and when I turn to the on position I get spark. I tested the spark by holding the plug against the engine. The wiring harness is very similar to the one on my X2 pocket bike. I had it started for 10 seconds after I pulled it 100 times and that was it. Messed around with the idle screw and throttle for an hour and still nothing.
For the spark to be considered strong enough to fire the engine it must be able to jump a gap of atleast 4 times its specification from plug end to engine fin which is around .120"........A tester like this helps out heaps.............http://www.nationaltoolwarehouse.co...HqMVnKcd2NbW-G49AtGmktuI6b3dKm77Ud5cO-gvw_wcB....So does a dark room.

I have quite a few coils in a box gathered over the years that will give ya a descent shock but wont fire an engine and never will.........coils get weaker everytime you ground them out to kill the engine..

Sometimes the magnets and coil thong ends get rusted up and cause spark weakness and pulse interruptions also known as misfires........Make sure they arent rusted-up..If they are rusted remove the coil,,,de-rust both halves with sandpaper and reassemble with an airgap of .020" then retest.....Id also swap out the plug just for reassurance because quality control and pride in your job went out the window 8-9 years ago..........Good Luck
 

·
Registered
Joined
·
5 Posts
Discussion Starter #8
Bad news: I took the working pocket bike around the block and ended up snapping the connecting rod just under the piston (i dont know how).

Good news: swapped the coils on the bike and the other one now works like charm. So I guess it was a bad coil that caused the no start issue.
 

·
Banned
Joined
·
24,164 Posts
Never broken a rod end yet. What does the piston pin rod bearing look like? That what usually goes first, if it was to loose and caused to much friction and heat, I guess the rod might break.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #10
Ill pull it apart and post the pictures. Im guessing the rods broken because the I cant turn the motor over. I pulled the carb and manifold off and I can see some damage to the piston. Could possibly be the piston pin.
 

·
Banned
Joined
·
24,164 Posts
If the piston pin clip falls out the pin will keep moving over and out one side of the piston and catch one of the main transfer top ledges on the way up, and it stops. The pistons, pin bearings and rod take a lot of stress. The metal on these bikes are not very good compared to Honda.
If the clip is not installed right the pin will come out the side, has happened to members here.
 

·
Registered
Joined
·
1 Posts
my pull start keeps melting or catching fire when I accelerate or let it sit can someone help me or tell me what I need to do to fix this problem
 

·
Super Moderator
Joined
·
2,685 Posts
Turn the pull start so it's faceing sideways then the air blowing across the head won't blow over the top of the pull start handle some bikes have a heat shield to prevent this from happening...
 

·
Banned
Joined
·
21,744 Posts
my pull start keeps melting or catching fire when I accelerate or let it sit can someone help me or tell me what I need to do to fix this problem
You're either missing the spacer or you're e-start / generator combo is smoked and needs,to be gutted...
 
1 - 14 of 14 Posts
Top