QT50 gearing/upgrades

Hi all, I'm sure this has been covered 1000 times, but I have a further question on the QT50 gearing mod.

My 85 QT50 runs like its brand new. Though it gets "on the pipe" at 24mph and hits that nasty 25mph rev limiter.

Heres my question:


Do I need JUST the pw50 gearbox/differential, or do I need the gearbox AND the driveshaft. Can I go w/ the stock QT50 driveshaft? PLEASE DO NOT GUESS.

If you have not performed this mod. Please do not reply. Not trying to be rude, I simply would like suggestion from someoen that actually has done the mod. Thanks guys in advance. Trying to get this puppy to at least 35mph versus 26mph. Thanks again.


Re: QT50 gearing/upgrades

hmmm my qt does 36mph with a 15 sha and a boss pipe, what is this about a rpm limiter?

Re: QT50 gearing/upgrades

I did that swap on my buddies qt. one drive shaft is longer than the others. I believe the pw shaft is longer than the qt's if I remember right. also he had problems with the qt's wheel not matching perfectly with the pw.s axle so I put the pw.s ring gear on the qt's axle assembly(this required a press).

also,he had no problems with a rev limiter at 25. I think you have another problem if your bike is hitting a wall at 25. if you have the factory pipe on there get rid of it(upgrade and upjet) or cook it and if everything else is good you should see more than 25.

Re: QT50 gearing/upgrades

Moto Photog /

Hey Kevin, thanks for the reply. I have seen many other folks talk about the QT50 hitting a wall at 25mph. You can tell its a limiter because when you're going up a steep hill (and im 220lbs) it chugs along and on the pipe it stays at a good 25mph even up steep hills. The second you're on a straight, it doesnt want to go faster than 25-27, cuts in and out a bit, but you can feel its not carburration. Hmmm... Seems some of the different years had different limits. Thats why I wanted the PW50 gearing, to keep the revs low, but to have it pull right along.

Re: QT50 gearing/upgrades

what about hardwiring it and just avoiding the regulator all together?

Re: QT50 gearing/upgrades

Ryan M

Email: goldenwesttires@hotmail.com

get ahold of this guy for details. he has done this mod and had a post in detail about it but I can't seem to find it now

Re: QT50 gearing/upgrades

Tate in Madison /

You know its possible there is a rev limiter on some QTs but I have never had one.

I have had plenty that feel like it but thats just four stroking, hence the pulling up the hill. They made the pipes/airbox/jetting such that it four strokes right around 26mph.

Go ahead and pull your stock air box and put a Uni filter on her or even just a panty hose. Hell you could even run it around the block without an airfilter to see what I am talking about. You will get up closer to 28mph or so.

If you are interested in making a fast QT50 I would recommend tracking down a Towny and robbleing the engine and rear wheel off of it. Better yet just get a Towny.

They do 35+ stock and get there way faster than a QT gets to 25. Townys have a 2 speed engine and also have the taller gearing like on a PW50.

They also have a bigger front tire, better forks, better rear suspension, better exhaust, better cylinder porting, and are superior in every way.

The only thing that makes me believe that it is possible that some QT50s do have a restriction is the fact that their ignition system has the whole 3 position switch with off/start/run. In the start position it will not rev at all. The spark is retarded to idle somehow. I am assuming its in the CDI but I never checked.

I am thinking Yamaha could have used the same device to retard the spark at whatever RPM=25mph.

Still though I have seen a lot of QT50s and most of them didn't want to go over 24-26mph but once you swap the air filter you get closer to 30mph.

Re: QT50 gearing/upgrades

i don't use that email anymore I use this one now since I changed my handle.

Pw's drive shaft and drive shaft housing is shorter.

Pw's have a taller final drive because they use a smaller rear tire, this means that with a pw rear gear swap you'll pull more mph while at the same rpm. It roughly comes out to a 10% increase in mph at the same rpm.

I did a complete tooth count of a towny engine and qt engine and they are almost the same. The qt's gear is the same as the towny's second gear. The towny has a short first that can be rapped the fuck out if you lighten the first gear's clutch.

I'll say this one final time. THERE IS NO REV LIMITER!!! The stock oil injector pumps toooooo much oil and makes the bike four stroke. This is because the pump not only pumps more oil with more throttle input(ala the split cable that goes to the pump) but also pumps more oil in the higher the rpm gets. That is what gets mistaken as the rev limiter. What the previous poster mentioned about the "start" switch limiting revs is true but it limits them soooo low you couldn't do but 5mph. In fact the "start" mode bypasses the normal cdi and engages a second limited cdi that has the limiter but also a wayyyy higher voltage spark. But again you wouldn't do more than 5mph with it selected to "start" so adjust your pump.

To adjust your pump you need to take off the plastic cover and loosen the pumps jam nut and then turn the adjuster nut and then re-tighten the jam nut. Which way you turn the adjuster nut i forget but even the pw50 manual goes into great detail about how to take a dial indicator to fine tune it.

To use a pw50 rear end you either need to press out the axle shaft from the ring gear and press on the pw's ring gear onto the old qt's axle shaft so the axle shaft is the same length or just use washers to take up the slack. Using washers allows you to later run a right side swing arm if you go with a towny engine like I did or fab up your own right side swing arm like I did before getting a towny engine.

If you want a pw50 rear gear and housing email me, I got two extras. I'll trade you for the stock qt rear gear and housing as I want to start to hit the track soon and I think I'll need to tune my bike for acceleration more than top speed as it's a go kart track.

If you got anymore questions just ask.


this is my qt

Re: QT50 gearing/upgrades

yeah and hard wiring is super simple but if you want to do it just to bypass the supposed rev limiter, don't. Just adjust the pump.

Re: QT50 gearing/upgrades

BryAn eurism /

Clarified: get PW gear and housing

Unpress shafts from host gears

Swap and press. = stock axle shaft + PW gear and housing

Rev plate; piston in stock position seriously blocks off generous exhaust port @BDC. Stack base gaskets, aluminum shims or Masonite to bring up exhaust floor flush to piston crown

Deck barrel by the amount you raised it. I used a Dremel in a drill press attachment with a diamond wheel. You can get by with that big fat grinding wheel they sell at Big Lots chucked in a drill and true it up relatively OK rubbing it around on something flat and gritty

Pipe is what wakes up the whole combo, header length preserves just enough bottom

Still running stock carb reeds & jazz, with a bit of piston slap, Radar poled me @37 being 3/4 in the groove, posed bolt upright with my tools on the back. Could go more aggro but why wreck a good daily?

Re: QT50 gearing/upgrades

You can switch to premix and bypass the pump so you always get the right amount of oil. Also you can get an aftermarket filter or just drill holes in the stock airbox and adjust the jetting to help. Those are just some simple quick cheap ways to run better at higher speeds without a lot of mods.

Re: QT50 gearing/upgrades

Hoosier Dude (Moving Targets) /

yep, shafts are different lengths, gotta press em out and swap.

pw and qt gears have a 1 tooth difference, so this mod wont gain you too much.

gotta delete oil injection, plug the hole, use oil tank as reserve gas tank

delete airbox. needs more air.

after getting an expansion chamber on her, (i chose an estoril)

I'm doing 45 on flat ground

I had to do a little chopping/jetting, she is thirstier now.


Re: QT50 gearing/upgrades

gps video please

Re: QT50 gearing/upgrades

Hoosier Dude (Moving Targets) /

for what? will that make it go even faster? where do I hook it up?

no seriously...

o.k, I'll get out my helmet camera and my global positioning system, and get right on that.

this matter deserves my immediate attention, I just cant stand my credibility being doubted.

you do those same mods on a qt, you will do 45... with that little ped, it feels like you're defying death.

by the way, I dont even have a gps, my speed was tracked with a vehicle alongside, a few different times and a few different vehicles, and hey, maybe a few mph off or inaccurate or whatever, but it dont matter, I wouldnt want to go any faster.

and short of buying an expensive kit, I've done about all the mods I can do for top end speed.

Re: QT50 gearing/upgrades

only with a special made pipe i could hit 44 on gps but it was unrideable as the power would only kick on right below 40 and this was even on my two speed engine. I doubt all but gps as car speedos cant read low and must read high or car manufacturers would be blamed for speeding tickets. This has already been discussed.

Re: QT50 gearing/upgrades

Hoosier Dude (Moving Targets) /

your right ,if you couldnt do it, it cant be done.

oh well, even if it reads +10 mph, I'm still doing 35 on a qt50, which isnt that disappointing. what is disappointing is your insinuating that I'm a liar.

a lie is a fabricated story which is completely untrue.

all i did was post some specs and my top speed, as read by a device called a 'speedometer". I dint make anything up, or even embellish.

so I'll see your pinnochio, and raise you a

Re: QT50 gearing/upgrades

If the gear change is only 10% it would be must easier to tune for higher revs to make up the difference. And almost any stock ped can be massaged to do 43-44 mph reliably

Re: QT50 gearing/upgrades

The down fall of the qt is the intake and reeds. unless you make your own intake and have built a four pedal read block it's kinda hard to make one of these turn super high rpms. This is why it's easier to upgear. Pushing one over 40 on truly flat ground with no wind is a great accomplishment(especially if still rolling 50cc). Going 60cc is another option but your theoretical redline goes down because of the weight of the piston. IDK but you are like the 20th person to post 45+(I even spotted a 50+ recently) but no one has put up a vid. Hell if someone would just throw up a vid of a 30mph qt they could truly lay claim to the fastest qt as I see it. Tuning these things is quite hard as there is almost no aftermarket(especially if you want to stay 50cc) so when someone spouts off ridiculous shit and mentions how little work it took to get there I call bs.

Re: QT50 gearing/upgrades

sure your tach is functioning accurately while running it on the stand.

Re: QT50 gearing/upgrades

Hoosier Dude (Moving Targets) /

ryan, you did 44 then? where's your video?

you're a LIAR unless I see VIDEO.

any day of the week- I'll bet you $1000 my 50cc stock jug qt will beat yours.

I'll put my money where my mouth is, we can do it at a rally this summer or whenever/wherever you like. titles go in the pot too.

Re: QT50 gearing/upgrades

the difference between me and you is that I plan to make a gps video as soon as my bike is back up and running. And you seriously don't want to bet against me, that's just throwing money away though I doubt you'd ever pay up.

Re: QT50 gearing/upgrades

my qt does about 36 GPS 'd with a boss pipe, 15 sha with stock top end gearing ect, and I agree with what was said above anything over 30 on that things is more then fast enough

to me 36mph feels like I'm out of control on a child's bike going down the side of a mountain

Re: QT50 gearing/upgrades

_And you seriously don

Re: QT50 gearing/upgrades

Hoosier Dude (Moving Targets) /

he tries to call me out because I dont have a gps video,

then he claims 44 mph, and doesnt have video himself.

and then he's all like "yeah, but I'm gonna make a video, as soon as my bike runs"

my gosh, you cant even race me with a broken bike, now can ya?

I wouldnt bet you, because you've proven yourself somewhat of a retarded, liar type

Re: QT50 gearing/upgrades

you should have seen the first pipe he made for his qt. bragging about the million cuts and welds he did and yet it still looked like a pencil dick pipe. people were trying to tell him that the pipe was holding him back but he couldn't bear the thought of someone else being a better tuner than he was. yep, pretty much douche from day 1.

Re: QT50 gearing/upgrades

i call bs. qt owners everywhere seem to be the kids from jersey. I see nothing wrong with dashing your make believe speeds with actual measurements. I am proud to be a dick.

Re: QT50 gearing/upgrades

see what i mean?

but where, oh, where are YOUR actual measurements, Mr. Dick?

Re: QT50 gearing/upgrades

so if I can gps vid my bike doing two runs, once up a street and once back down the same street, both times busting out 50 with only 50cc will I get the grand??? For that I may put my handle bars back on and just use a bar for my nonexistent rear shock and take a ride.

Re: QT50 gearing/upgrades

Hoosier Dude (Moving Targets) /

that's not a race, that's called proving the bullshit your trying to feed us.

In a proper race/wager situation, two individuals meet on neutral ground, a trusted third party holds both participants money, and the race takes place for a specified distance, after which the winner gets the spoils.

this wont be happening in this situation because I'm not racing on qt50's,

or any bike, for that matter, against a retard. sounds dangerous.


you dont know how wagering or betting works, or even how races work, so I dont consider you a worthy opponent.

you've made no friends here kid, why dont you move on.

go update your facebook or something, tell them all how much you know about mopeds or how fast your qt50 goes.

I initially replied to this thread to help ol' boy here with his tuning questions,

not to argue with some turd.

Re: QT50 gearing/upgrades

if I proved my bullshit would that then make my bullshit not bullshit but fact??? I'm no scientist but I think that's how it works.

Wait and now you don't wanna race because I'm a retard because I called you out for lying? How does that work? Saying you want a heads up race is laughable, actually quite.... retarded, as some would say. I'm in no hurry to run out to the midwest to race you but if you're ever over here I'll be more than happy to take your money since your pride mandates you loose it. Though I have this funny feeling that once you listen to my engine in this video you're gonna skwirm out of racing me, curses left in your wake.

You're defending your sinking ship.

just choke on the video then stfu

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