Moped Riders Association

mccannable · Net Rider Joined: 22 Jan 2008 Location: florida

this might have been done before, i tried searching/looking but nothing i have found yet.... i have it about 40mph on a stock 80 silver bullet flat ground, maybe a tail wind. i only weigh about 130 lbs.

42mph downhill.

MgsissonVT · Net Rider Joined: 03 Mar 2008 Location: Blacksburg, VA

I'm using a friends Puch Magnum, I'm 240 and I can get it to 47mph on flats, who knows down hill. He has it kitted with a polini 70cc, 14mm bing, bullet exhaust (I think). So fun to ride around town. We also have a kitted garelli ssxl that will prolly hit lower 50's (andy is still breaking it in). Fastest stock ped we've seen are newer tomos's around the low 40's, and a nice garelli running 35-38

jswift · Net Rider Joined: 05 Oct 2007 Location: GA

My lard ass will do 40 with massive tail wind on a 2007 ST, and that is scary, due to the crosswind. Today several X winds nearly took me out. I slowed down.

vuarra · Net Rider Joined: 03 Mar 2006 Location: Hamilton ON

Level ground, I've hit 72 km/h (44.7 mph)

Downhill... 81 km/h (50.3 mph)

Tab · Posted: Tue Apr 15, 2008 8:45 am Post subject: re: Post your top speed?

Currently...

Custom Revival - Airsal A-35 kit with speed sprocket - 46mph
Streetmate Type R - Airsal A-35 kit - 43mph
Aprilia Scarabeo with Polini Corsa - 55mph (62 on the speedo)

bigdog456 · Net Rider Joined: 14 Apr 2008 Location: clovis ca.

i got a sick 85 yamahopper up to 34 mph. nothing special done to this pile. it's just haulin my ass all over town at 102 miles per gallon. got to love it. have fun. a.j.

crx7 · Net Rider Joined: 18 Oct 2006 Location: Austin, Texas

42 Uphill, coming back from school, it's a decent hill which tires me out on the bicycle.

Haven't taken it to top speed yet as I'm "breaking" it in. Sucker starts to haul when you hit 35. I need to find a safe place to top speed it, and we'll see what is does.

70cc Qt50 with all the common upgrades.

xrongor · Net Rider Joined: 15 Nov 2005 Location: montana

exactly how did you get a 70cc QT50? even the stock YT60 cylinder only bumps it to an actual 54 cc's and there is no way to bore it out enough to even get an actual 60cc's out of it.

randy

crx7 · Net Rider Joined: 18 Oct 2006 Location: Austin, Texas

Whether it's an actual 70cc or not, I don't care, either way it's much more powerful than with the YT60 piston. I believe it's a 48mm piston and the YT cylinder is bored about as far as you would want to go. Don't know what calculations you're going by for the displacement, but the cylinder is much larger than the stock 50cc. For this reason I'm not using the 50cc head as the area doesn't match at all. YT60 head is close enough and probably gives good compression, or as much as I'd be comfortable with.

Exactly how: It's a piston from a Zuma/Jog/Vino 70cc kit. You can pick up the piston by itself every so often cheap on ebay, and it's available on some websites for more, just make sure you get the 10mm wrist pin version. The piston a bit cheap, I'd like to find a better quality one if anyone can find one of the same dimensions.

Do you have a figure on the stock bore and stroke? I've got 39.0 bore by 41.5 stroke which gives 49.6cc stock.

Measured diameter of my piston is 47.6. Giving a displacement of 73.85

crx7 · Net Rider Joined: 18 Oct 2006 Location: Austin, Texas

Sorry I multipled the wrong number for stroke. Stock is 41.5 bore by 39 stroke. With the 47.6mm piston it the displacement is 69.8cc.

YT 60 bore x stroke is: 44 x 39.2 which gives 59.6cc How'd you get 54?

xrongor · Net Rider Joined: 15 Nov 2005 Location: montana

so you swapped out the crank? both the YT60 and QT50 have the same crank, hence the same stroke of 39.2 mm (3.92 cm) unless you swapped it out you cant change the stroke.

as per the manual, stock QT50 has a bore of 40 mm which comes out close to 50 cc's.

stock YT60 has bore of 44 mm, or a radius of 22mm (2.2 cm)

pi r squared times stroke = bore

3.14 * 2.2^2 * 3.92 = 59.6

i had it stuck in my head it was a 42mm bore i guess. sweet i just gained 5 cc's by doing nothing hehe. ok im with you on the displacement. sorry my bad.

yeah i agree about the head. stock QT50 probably would be too much. i worried about it even on a stock YT cylinder (when you kill the ignition you get that nice clunk of the piston rebounding, lets me know i got good compression still!), but not so much so after 2k miles with it.

dang though you got that wall pretty thin. the whole section of the cylinder that sticks into the engine is only 51ish mm wide. shave more than that and its gone! ah well, they're cheap. i assume you got PW gears on it, i bet stock QT gears you could pop a wheelie!

randy

Targa5150 · Posted: Sat Apr 19, 2008 11:42 pm Post subject: re: Post your top speed?

45 top speed on my 2005 Targa LX (Bee attractor) on flat land..

Stats: 220lbs (me) / Stocking air filter / #66 jet / Bi-Turbo / Speed Sprocket / Minor Exahust porting

Not bad concidering its got 18,000 miles on the original 50cc cylinder.. :)

Alan

pehuskey · Posted: Sun Apr 20, 2008 1:26 am Post subject: re: Post your top speed?

yeah...I would say that's pretty good, since I can't get mine going much over 42-43 on the flat...but I have a lot of hills where I live and it doesn't lose much on the hills.

JD · Posted: Sun Apr 20, 2008 8:36 am Post subject: re: Post your top speed?

mac,

Take most speed claims with a gram of sodium chloride. The speedometers on these bikes are often wildly optimistic. To get a reliable reading, you've got use some sort of electronic timing device (radar, GPS) or attach a speedometer that you can calibrate.

We did a rough calibration of our TGBs with the car and learned the speedo was about 15% optimistic, so the "50 MPH" we were riding yesterday was really about 43 MPH.

jd

duck · Posted: Sun Apr 20, 2008 7:41 pm Post subject: re: Post your top speed?

I've been fast enough to know I shouldn't be going that fast.. aproximatly 47 on the speedo.. probably 42ish in actuality....

had my front tire pop... now I'm sticking to 40ish