top speed and mpg loss

[iantys46]

i have a pcx 125 now done 20,000 miles when i first got it it bounced off the rev limiter at 62-63 mph and did around 106 mpg.
like another guy on here i have fitted michelin city grip from and rear and had it serviced and every time i have it service it seems to lose around 3mph and 3mpg i have had the belt changed around a year ago. It is now doing 55mph and 98mpg and seems to struggle to achieve this speed where before the engine was wanting to go faster but the electronics cut in. It easily hit 63mph even two up.
The local dealers i have spoken to don't seem to be conversant with this problem but i know others have had similar issues.
Any advice would be greatly appreciated

[dkazzed]

Dirty air filter? Dirty fuel injector? Spark plug needs replacement? Worn CVT components like rollers, clutch, etc.? Needs a valve adjustment?

Those five would be my main suspects, sorted by easiest to hardest fix.

[honkerman]

It would be good to have more information.

Did anything happen prior to this: Recent service? New Belt? Long time unused?

Are the tire pressures right? How does the spark plug look? Always check the little things first.

Have you had regular services done per the service schedule in your manual?

The reason I ask is, it could be a simple matter, or something more complicated like worn CVT parts (belt, pulleys, variator, secondary clutch), or a leaky valve, or a fuel delivery issue.

Best to start by checking the easy stuff.

[Mel46]

You do need to add your location so that we can better determine if the environment may play a part in this. Also, the rollers should have been replaced at some point in that time. If not, then do that, either using the OEM ones or get some NCY 13 gram rollers and give it some pep. How many miles have you put on the new belt? As it wears it will affect your top end and gas mileage.

[txpcx13]

I really can't add too much more. If you follow the recommendations above you should find your problem.... My one small tip is to change the fluids yourself (oil and tranny) to make sure you get it done properly and the stealership isn't cutting corners.