Help me figure out this mystery
 

Hi

I have a Znen 150T scooter, lately it has not been running right at all, it starts and idles, but the idle is a bit "rough" when you sit on it, it almost feels like the bike is slighly bucking forward, its slight but noticable,,,you can ride this thing for about 10min,Go WOT, then you notice a slight loss in power and on throttle it starts to hitch or skip, then full throttle bog and stall,,,wait 10secs, its starts back up and is boggy and hitchy and will stall out,,,,when I put the bike in the garage it smells, hot or burned oil kind of scent and if you look under the bike later you will see oil drops, here are the things I have done so far with no success



-3 different new carburators

-new plug, battery, fuel petcock, CDI and IG coil

-oil change

-valve clearence .003 and .004 respectively

-sprayed carb clean on hoses on idle to detect vaccum leaks

-replaced some of the fuel and vaccum hoses

It SEEMS that when the bike get hot on WOT is when all the issues start

The symptoms listed are consistent no matter what I did, Im not sure what to try from here, if you have any ideas im open ears

TY for you help

Are you sure its really carb related? I would check:

It could be a main seal allowing air in. This really affects 2 strokes but it could affect a 4 stroke (like yours) as well. I would inspect inside of the transmission cover for excess oil, actually it should be relatively clean in the transmission. If that side looks good I would check behind the stator. Much more involved but I've had the main seal behind the stator leak on a Zuma 125.

Related to above, if you find oil in the transmission/belt area determine if its coming from behind the variator (main seal is behind it) OR if you have a leak behind the torque driver. I've had a few rear seals on the reduction box leak. High miles, doing burnouts, neglecting changing the gear/reduction box oil are just a few causes. Easy fix though.

Last thing I can think of right now. Is the intake that the carb mounts on rubber? Is there any cracks in the rubber? The Honda Helix is famous for the carb mount splitting, causing annoying running behavior.

Post your findings when you figure it out and feel free to ask us any further questions.

It could also be running hot from poor carb settings. New carbs are never set, you have to dial them in.

Could also be a stator failing.