QT50 or QT60 mods

[xrongor]

[82QT50]

[xrongor]

[lars91]

Hi, I also have a 1984 QT50 that runs good but will not go over 25 MPH with the similar symptoms mentioned here. I am going to try the general upgrades posted here and see what happens. I assume you guys are drilling the airbox on the rear half of the cover and not the front? 3-4 1/4'' holes?

Larry

[pete in pa]

[Aceface]

MLM (Motion Left Mopeds) just came out with an awesome expansion chamber for the qt. bolts right up. badass side-bleed, best on the market. also, pw rear gears dude

[pete in pa]

[pete in pa]

Well I've got the 60 stuff on the way! In the mean time I took off the top end and was surprised to see blowby (black streaks below the rings) on the piston.

This is on an 81 with 2300 miles. It was running fine with good power, does this mean it was never broke in correctly?

For the 60 I'm going to use NON syn oil at 50 to 1 and I'm not going to abuse it, but I'm not going to baby it either. I will break those rings in!

[pete in pa]

Well the UPS guy came at 6:30 tonight and by 8 it was running. In the process of breaking it in but even with that I can feel the power! 1/4 throttle picks the speed up like full used to.

I'm running 50 to 1 dino oil and will switch back to Amsoil synthetic after break-in.

I've got an 80 jet in there, once broke in I'll see if it needs lowered. BP6HS Plug is more black than brown. Rather have it too rich than lean and risk a seize.

[pete in pa]

Just did the PW ring and pinion gears. Big improvement! Now cruises at 35-40 on level ground and I've had the factory speedo needle pointing PAST straight down (6 o'clock) downhill. I'm geussing 50+ mph!

Still only at 50 miles on new 60cc upgrade, so it's still improving. Performance keeps going up.

Thinking about stiffer clutch springs since the point of full clutch engagement is now 15 mph.

Now total list of mods: 60CC upgrade, PW50 gears, air filter housing lots of big holes, 75 main jet, 50 to 1 premix, 2.25 kenda tires front and rear, what's next?

[pete in pa]

Just saw the Malossi kit is available again. http://www.treatland.tv/yamaha-QT50-YT6 ... 318007.htm

this one has 45.5 mm bore instead of my 44mm. how much more performance would this get me?

Also this kit looks good for others wanting to go to 60cc.
http://www.ebay.com/itm/YAMAHA-QT50-60C ... e9&vxp=mtr only $85 !!

On my current setup what will Boysen reeds do for me?

Will milling the head to get more compression?

What will get me more power?

EDIT: Malossi is a bit optimistic with their 70cc.

Stock QT: 49.26cc
YT60: 59.61cc
Malossi: 63.74cc

For the price I'll keep the 60cc for now.

Current setup: Yamaha yt60 cylinder, piston, rings, head, PW50 rear end gears, Qt50 muffler rear bored out, carb with 75 jet, air filter box with lots of holes, 50 to 1 premix with amsoil syn. oil, BP6HS plug.