ybr 125 surging?

[samybr]

hi all, new to forum new to biking!
have just bought a ybr 125 2006, non fuel injected model and have a problem with it.
when trying to hold a steady rpm it rises and falls independently and it feels like the bike is surging at full throttle. Have replaced the coil, regulator and spark plug, cleaned the carb out and checked for any loose wires, does anyone have any ideas of a problem with this model . cheers sam

[Damon]

could it be an air leak somewhere?

[samybr]

i thoght that too but o ring seals inbetween carb and manifold seem to look ok.but under the tank there is a diaphram 'thingy'attached to the top of the engine by a metal tube.could it be this??

[greenman]

get a tin of wd 40 [assuminig it has a rubber manifold[carb to head]let bike tick over and spray wd40 allover the rubber [yes it will give off fumes /spray carb to rubber then cover all rubber joints /dont hold back, if engine rises theres ye problem

[greenman]

o rings might be ok its the rubber that that splits but you cannot see so while it ticks over and you spray the rubber it fills the cracks and causes the engine to rise [not sure what you mean by rubber pipe /is it coming from head to airbox [if so its a breather take it off and see if its clear [on tick over does it rise by itself

[samybr]

tick over rises and falls a little, but it is more noticable at a steady 40 mph or above, almost like a miss fire but its not miss firing. yes that is the pipe from the head to the airbox its not rubber though its metal it has a diaphram in line looked like more than a breather?

[Damon]

you dont have the choke on do you?