MOPED ARMY

In my opinion the QT50 is a great platform, but I don't think you'll see 55+ with that mild setup. The biggest limiting factor in the QT50 is final drive ratio, which I believe can be swapped out for a pw50 gearset for more speed, but you'll need to setup the clutch for proper engagement and such. Also you haven't factored in airbox solution, replacement cables etc.

i had a stockish QT50 going 40+ with different final drive gears. you get them from PW50 forums sometimes.

my stock-ish MJ50 (more like an SG50) would get up over 45mph. isnt SG50 also a 2 speed?

I think a qt could do 55. You have to go to the pw gears and I laced up a 16" rear tire for it. This particular pipe is more low to mid range IMO but I could be wrong on that. That's just what it seems to me. So anyways, I've got the gearing to do those kind of speeds now. Now it's just a matter of getting the engine to do it.

Actually this thing has pretty good acceleration which is a combo of the pipe and the HPI system and I'm using the HPI CDI with the more aggressive curve that advances timing in the low to mid rpm range and then retards it slightly in the higher rpm range. You can look up description on treatland's site as to how it exactly works - I'm using my somewhat faulty memory.

I'm at just under 51 mph. But I think just raising the exhaust port a little could give me a tiny bump in top speed. Switching to a different pipe would help too and I could play with different timing settings on the HPI. But after taking several nasty falls learning to snowboard, I'm a little hesitant of experiencing similar falls on asphalt. Despite it's small stature, the qt does feel pretty stable at higher speeds though (I've added a crossbar which helps). Obviously the stock brakes were not meant for this.

Short answer - yeah it think it could be done - 55mph on a qt.

this is from my thread. i was asking about putting a vm20 on a 50cc motor.

"You can attempt to put a VM18 on this, but general rule of thumb is you want venturi size to be at most 50% of bore. So, on a 38mm~ cylinder you wan a ~18mm carb max (and that's theoretical maximum, so including a pipe and porting). Aka, a stock port and intake, and a 12-15mm is more than adequate and youll get better response from the smaller carb"

TM24 does seem a bit huge for a stocker 50cc. I run a tm24 on my nu/nx motor, but im also running a heavily modified h2o setup that spins the motor to ~10k rpm

The biggest problem with running a large carb on small cylinder (especially on an single speed, fixed ratio transmission) is that you're really never going to get AS accurate tuning as you could with a smaller, proportionate bore, because your intake pulse/draw is weakened. Generally speaking, in flow dynamics you lose fluid speed velocity the greater your volume is. Big bore carb means air travels through it slower and has a slower reaction to throttle input changes because of this. In addition, many modern carbs are HEAVILY reliant on a strong intake pulse to properly meter

This is really true of mikuni carbs, where EVERY VM20 bike I have ever built or worked on whether for friends or Second Stroke/NYC Mopeds build, ran decently with the factory jets the VM20 comes with.

Now, I can tune it in from there, but their pulse metering is so good, they typically just work, unlike a PHBG.

Again, this can be motivated through many ways to get decent results, but in the end I will typically err to smaller carb per build.

15mm carb on a 44mm cylinder is not too small. That's pretty standard and healthy, imo.

I run a 12.12 SHA on my 46mm Pinasco kitted ciao and love it. I have no issues tuning and it runs cool and well.

And to answer the OP: look at what Jack mentioned a few replies down. All the the items in your buy list, PLUS HPI, relaced rim, new gears, and a bunch of know-how, and he's at 51mph.

Could you get 55+ put of a QT? Yes.

Will you get it out of the parts listed in the first post? No.

The MB5 is also a weak comparison because it's about 100 lbs heavier and it's output is not even that high compared to it's contemporaries.

It is a great bike tho.

I put EBC brakes on front and rear, probably best out there, way better then stock or another off brand I had. They're still inadequate. Why are they so narrow? They're not even using all of the drum.