whats this ajustment on zongshen engine???

[zongshen fury]

Hello again all,
could anyone tell me what ajustment thing this is,its on a zongshen 250cc pushrod motor, if u take the bolt out of it you can turn it in and out and i have no idea what is is or what its there for/used for...in the pic below.....
Thanx again

 

[mattbombers]

timing chain roller

 

[zongshen fury]

its a pushrod motor..no timing chain.....?
the bolt is up above,its really long and u have to turn it so the mark is facing upward for the bolt to drop thrugh.. i took the bolt out one time and turned the motor over,(but not start it) and it was like something was pushing it coz it was goen in and out so i thought it mite have been some ajustment for the cam or something????? any ideas???

 

[rumble]

Something to do with the cam adjustment.