Lost performance of Sento 50 - HELP !!!!!

[dbcove]

So not too long ago my Kymco Sento 50 ( GY6 engine ),was very spirited with a top speed of 45 and I'm a 220 pound guy. Then, the performance went away. Now sluggish up to 30mph top speed on the flats. If I try to give it more throttle it just sounds like its bogging, muffled sound. So I did a compression test dry and wet. Wide open throttle with 5 revolutions provided by the electric starter. Dry was 150psi, wet ( 2 TBSP Marvelous Mystery Oil ), and got 190psi. Looked for any apparent cracked hoses, cracked intake, changed plug ( although it looked good ), no change. Been running small  amount of gumout through it, not helping. Doesn't have problems starting or idling, just running really lazy.
Need you folks and your expertise to guide me down next steps. Thanks in Advance !!

BT 4 Stroke... thx

[wkreps]

Welcome to the forums. You have a good air filter in it. I once had a old Yamaha 50cc and it bogged under acceleration (had NO air filter in it). Put in a new one and she took right off.

[dbcove]

Air filter good. Looking for feedback on compression readings...anyone ?

[blue]

Sounds like time to do the valves.

[dbcove]

Not a pro here so I apologize for asking blue, on what do you base that assessment ? And if that is the case can I just purchase a new top end with the valves included ? Can you suggest a site with quality parts for this task ? Thanks in advance!

[Chris0381]

Something similar happened to someone in the ZX50 forum. I believe he discovered they didn't put a head gasket on at the factory and vibrations eventually knocked the head loose enough to lose compression.

[aaron8]

Clean the carb