I've got a question about the Zongshen ZS250GS.

I've recently bought one (a few weeks ago) on ebay, only a few hundred miles on the clock, and only a few years old.

but this thing feels slow.
don't get me wrong it gets up to highway speed (70MPH), but it seems to struggle to get there... -and whilst that is the legal max so I don't have a lot to complain about, a little bit more is always nice, you know if you're passing someone etc).

I used to have a Lifan 125gy-3 I could understand a not too blistering performance from a learner legal 125, but I was hoping a bit more from the (around twice as powerful) zongshen. (I could happily get to around 60 - 65 on the 125, and could push it all the way to the redline at 12k, it's happily sit at 11k all the way home on a 40 mile drive and then start on the first kick the next morning ready for a boat load more abuse.

(after owning the bike for three years I gave the bike to a guy, now and again I pass it, or see it in the street and think I used to have a bike like that, then I see the plate and realise it was my bike)

but the 250 gs just seems a bit lack lustre, on a dual carriageway it sits at around 70MPH and struggles to get any more, that's top gear with the revs at around 7k, so only just over half way around the clock... it just won't rev any higher, or go any faster. no matter how much I try to "tuck myself in, or going downhill, or wind direction.


I'm wondering if the bike is limited? underpowered, or would just struggle to cart around a fat git such as myself, (at 16Stone / 220lbs).

(I don't need uber speeds out of this machine, the reason I have this machine is a fuel economy based decision, riding it around so far I've gone around 100 miles on a little over 1/3rd of a tank, (so getting around 80MPG)...
if I want speed I've also got a GSXR 750... though the economy of that is about half the Zongshen, and road tax is around twice!)

TL:DR
my ZS250GS seems underpowered,
is that just how it is? or is this indicative of a problem?
what mods are cheap and sensible for eeking out a little more power.
what sort of power gains can be expected (and are these also dependant on wishful thinking and wind direction?)

I know that this bike is always going to be a sub 90MPH commuter more suited to towns than highways... but my commute involves towns and highways