if you haven't jetted your carb then the aftermarket can and filter can actually slow you down, my 90mph pre mod was on the big straight on the a1 near st neots in mid summer, i only get 85 in 5th now because of the larger front sprocket, my other mods just give me a tad extra power, i've never checked my valves or changed my cam or polished the head or carb, my engine is 100% stock seriously if you live close enough i'll meet you and you can see for yourself, just don't drop the f*cker lol.Pics of NOS ooorrrr...
Ps I think you are on drugs, as I already posted , mines struggled at 82 and I was tucked, down a hill, no danger are you getting 85 in 5th, just no way.
And mines has a custom downpipe, cone air filter and scorpion end can.
So mines isn't completely standard either.
The only person on here who can say anything about the mods is Carlos, he knows his stuff and I think he seen his go to around 18 bhp after head skimmed and race cam, compare that to a 2t and 18 hp is a poor 125 2t so would maybe only get around 90-95 then.
And I checked my valve clearances yestarday and they're perfect, so my bikes running mint.
Never had anywhere near the speeds your saying.
I'm calling bs.
my nos kit is pretty basic tbh it's closest to this one http://www.ebay.co.uk/itm/Dirt-Mini-Pit-Pocket-Bike-ATV-Quad-50-80-90-110-125-cc-NOS-Nitrous-Oxide-Kit-/330784273367?pt=Motorcycles_Parts_Accessories&hash=item4d044773d7 i just have a different delivery system.