Engine jerking and hard to start

Jeramie

New Member
Joined
Dec 7, 2019
Messages
24
Hey guys ... Ive been trying to figure out why my bike is jerking alot and wont even start sometimes now ... It jumps and jolts when trying to start ... If it starts it jerks real bad for almost the whole ride and sometimes it even shuts off the bike ... Hope its not toast ... Hasnt started at all today ... Its a 2 stroke 66 cc slant head ... About 200 miles ... New carb ... Just like the one it came with ... Please help
 


mark20

Well-Known Member
Joined
Sep 26, 2018
Messages
762
Hey guys ... Ive been trying to figure out why my bike is jerking alot and wont even start sometimes now ... It jumps and jolts when trying to start ... If it starts it jerks real bad for almost the whole ride and sometimes it even shuts off the bike ... Hope its not toast ... Hasnt started at all today ... Its a 2 stroke 66 cc slant head ... About 200 miles ... New carb ... Just like the one it came with ... Please help
check the if the cdi boot is making a good connection to the spark plug. and check to see if the magneto isnt loose inside the engine. that or the wires are not making a good connection.
change the sparkplug as it could be fouled, i use a NGK B6HS (if its really black, then run a less oil mix ratio like 40:1, or jet it leaner)

if that doesn't fix it, its the cdi and magneto crapping out. about 13$ to replace both.
https://www.ebay.com/itm/CDI-Ignition-Coil-Magneto-Spark-Plug-For-50cc-66cc-80cc-Engine-Motorized-Bike/372365902190?hash=item56b2bcc16e:g:5ogAAOSwzFRdU48O
 

YetiWoodz

Member
Joined
Dec 19, 2019
Messages
217
I had the same exact problem after I finished building my bike. My friend fixed it for me and I was there with him. Nothing was broken or needed to be replaced. I forget what it was. It may have been something with the clutch. Also every time you shut off the engine, this switch moves back, you have to move the switch every time before you start your engine so you get enough air into the carb.
92820

But you did say you rode this 200 miles so this is probably not the case.
 

YetiWoodz

Member
Joined
Dec 19, 2019
Messages
217
Check the chain and the sprocket too. Make sure its greased and that the sprocket is not bent. My guess its the spark plug. They only last 50 or so miles. If the spark plug is bad then you won't get proper spark which will make it jerk while its trying but failing to start.
 

Chainlube

Active Member
Joined
Jan 5, 2020
Messages
305
That's a good one, it doesn't even have a white wire attached so you don't have to remove it.

check the if the cdi boot is making a good connection to the spark plug. and check to see if the magneto isnt loose inside the engine. that or the wires are not making a good connection.
change the sparkplug as it could be fouled, i use a NGK B6HS (if its really black, then run a less oil mix ratio like 40:1, or jet it leaner)

if that doesn't fix it, its the cdi and magneto crapping out. about 13$ to replace both.
https://www.ebay.com/itm/CDI-Ignition-Coil-Magneto-Spark-Plug-For-50cc-66cc-80cc-Engine-Motorized-Bike/372365902190?hash=item56b2bcc16e:g:5ogAAOSwzFRdU48O
 

Chainlube

Active Member
Joined
Jan 5, 2020
Messages
305
That is your choke lever, it should be down for driving.


I had the same exact problem after I finished building my bike. My friend fixed it for me and I was there with him. Nothing was broken or needed to be replaced. I forget what it was. It may have been something with the clutch. Also every time you shut off the engine, this switch moves back, you have to move the switch every time before you start your engine so you get enough air into the carb.
View attachment 92820
But you did say you rode this 200 miles so this is probably not the case.
 

RB55

Active Member
Joined
Sep 18, 2019
Messages
139
I agree with the advice regarding the CDI and spark plug. I was thinking about the rear sprocket but that would not prevent your engine from starting so that's not the issue. After 250 miles my NGK B6HS fouled and the bike wouldn't start or remain running. I would first replace your sparks plug and if that doesn't help then I would replace your CDI and magneto. Good luck!
 

Jeramie

New Member
Joined
Dec 7, 2019
Messages
24
Well thank you to everybody that reply to try to help me out but I'm an idiot it was just my spark plug still thinks guys
 

kaneto

New Member
Joined
Aug 27, 2016
Messages
5
I had the same exact problem after I finished building my bike. My friend fixed it for me and I was there with him. Nothing was broken or needed to be replaced. I forget what it was. It may have been something with the clutch. Also every time you shut off the engine, this switch moves back, you have to move the switch every time before you start your engine so you get enough air into the carb.
View attachment 92820
But you did say you rode this 200 miles so this is probably not the case.
This is the CHOKE lever. You only need to move it up for cold starts. It limits the air, thus making the engine suck more fuel.
 
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