Spluttering under load at high revs

Hi my vespa t5 with mallosi 172 kit is running well until the back end of the revs in each gear then it begins to splutter and occasional back fire but is intermittent. Have tried another cdi and plug but has no effect. Any ideas cheers 

Hello Chrismulliner,

thank`s for your email!

We think that`s because about a damaged pickup or a damaged coil.

Maybe the mainjet is also to small.


Kind regards

Mario SIP