THE OFFICIAL QT50 THREAD!

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re: THE OFFICIAL QT50 THREAD!

Postby wsemajb » Thu Jul 19, 2012 4:34 pm

I'm considering a winter project with one of these.

Neighbor has a garage-bound QT50 with 1400 miles on it. Extremely dirty and missing the carb but otherwise doesn't look like too much to get it breathing again. Plan to keep engine completely stock except for carb and pipe.

May try to improve front shocks/triple-tree and mount larger wheels. I'd like to do a minimalist rebuild of this bike. Stripped of all cosmetic plastic, replace large headlamp and taillamp with a tiny halogen units, remove instrument cluster, etc.

Any links to previous efforts to lengthen the drive shaft and tube? Would love to relace the hubs with 24in 28hole BMX alum rims and a nice sturdy high pressure lighter weight road tire...

Image

Any experience with a suggestion seen elsewhere on adding 4mm of spacer under the jug and milling same from top in order to take advantage of exhaust port volume that is blocked by the original design?
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re: THE OFFICIAL QT50 THREAD!

Postby Brad G » Wed Aug 01, 2012 2:23 pm

I've created a forum specific to the Yamaha QT50. My hope is that we can share tips and advice for the Yamaha QT50. I contacted Tab from this site and was granted permission before soliciting the QT50 forum.

It's hard to find sites dedicated to specific models but when you do it's sure nice.
Hope to see you there!

Thanks,
Brad

A.K.A. ~Focker
Link - http://qt50.darkbb.com
1980 Yamaha QT50
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Re: THE OFFICIAL QT50 THREAD!

Postby pete in pa » Sat Aug 29, 2015 5:47 pm

Anybody still out there?

I've still got my QT60. Just took it out for a run today, still works great, Still doing 40-45 mph.

Just noticed new rear tire wearing rapidly. Kenda 2.25-14 didn't have much tread when new. Next I'll do the IRC NR77 tire in 70/90-14.
1981 Yamaha QT50: Yamaha 60cc hop up, PW gears, stock pilot, 75 main, red Uni filter, BP7HS plug.
2006 Honda ST1300
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Re: THE OFFICIAL QT50 THREAD!

Postby YamahopperChris » Sun Aug 30, 2015 1:29 am

Hi, I just registered. I have a QT50 I hope to start restoring soon. I got it from my grandfather in 1992. I believe he was the original owner. It's been in a friend's barn for about 18 years. I lost the key. Can I get it running without the key?
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Re: THE OFFICIAL QT50 THREAD!

Postby YamahopperChris » Mon Aug 31, 2015 10:00 pm

Date on the frame says 7/79.

I'm not a mechanic but have some skills and can figure stuff out. If I start tearing this down is there an order? Should I bag and label stuff?
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Re: THE OFFICIAL QT50 THREAD!

Postby pete in pa » Tue Sep 01, 2015 5:16 pm

Here's a manual: man_yamahaqt50sm.php

Going by the wire schematic you can "hot wire" without the key but I'd find that key or go on ebay and get a replacement ignition.

Do a search here and read ALL the posts on the QT50.

If you need engine work just do the 60cc upgrade.

With a good clean up looks like a good bike.
1981 Yamaha QT50: Yamaha 60cc hop up, PW gears, stock pilot, 75 main, red Uni filter, BP7HS plug.
2006 Honda ST1300
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Re: THE OFFICIAL QT50 THREAD!

Postby YamahopperChris » Wed Sep 02, 2015 10:47 pm

I didn't even try to start it. Bad gas etc... I've been breaking it down, bagging and labeling things.

Lots of dirt dauber nests all through the inside of the frame, the headlight, air filter housing and under the fuel tank.
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Re: THE OFFICIAL QT50 THREAD!

Postby YamahopperChris » Wed Sep 09, 2015 6:47 pm

Anyone disassemble the oil pump? Mine looks like the one in the shop manual on 3-14 but mine has a spring that's not shown. I'm trying to clean all around it but can't figure out how to take it off.
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Re: THE OFFICIAL QT50 THREAD!

Postby porter1 » Tue Oct 13, 2015 4:01 pm

Hi, I'm new to this forum. I bought a qt50 2 weeks ago with no carb, but otherwise complete bike, I bought a carb off ebay and put in a new battery. It runs real nice now. I had one a couple of yrs ago but sold it, I was sorry I sold it, but I'm going to keep this one. nice thread on qt's, lots of good info.
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Re: THE OFFICIAL QT50 THREAD!

Postby pepper » Sat Dec 19, 2015 5:58 pm

The speedometer on my QT50 is not working and I've isolated the problem to the drive gear/meter gear in the front hub. I haven't been able to remove them. The drive gear appears to be held in by a rubber retainer ring. I don't want to destroy the ring since I think its no longer available. Any tips on how to do this? The service manual doesn't explain it.
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Re: THE OFFICIAL QT50 THREAD!

Postby pete in pa » Sat Mar 05, 2016 6:38 pm

Should have done this FIRST. Any of you with an old moped or ANY 2-stroke change crank seals from the start. If it sucks on the left it will get air in and mess up your attempts at jetting. Sucks on the right you pull tranny oil in and burn it. Mine was doing this and steadily getting worse.

Doing crank seals on my 81 QT50 (60) I looked high and low on the internet. Couldn't find if this could be done in the frame without separating the crankcases......IT CAN.

Service manual has a complete disassembly of the engine but doesn't tell you it's not needed for crank seals. Left side you have to pull the flywheel.

If you don't have or get the right tool Use this: http://www.harborfreight.com/automotive ... 66868.html Automotive pulley puller. $13 from Harbor Freight.

Just also buy longer bolts and nuts to hold the jaws on (in one review on HF website). Be careful inserting the puller jaws in there are magnets and coils back there. If you're careful, no problems.

My flywheel (and crank seals) are original. Took some work to break that flywheel loose.

Remove the timing plate. BTW you'll need an impact screwdriver. Lots of JIS screws.

Take a small drill bit and slowly, carefully drill a hole in the crank seal. Crank seals are metal inside surrounded by rubber. The bearing is right behind so be careful. Run a wood screw in the hole and pull the seal out. There are videos online to watch how to do this.

For right side drain oil, remove cover, try to save gasket, if not order one.

Put an all copper penny between gears and break the crank gear loose.

Remove clutch, primary gear and all else in the way. This seal you can pry out carefully with a small screwdriver.

Drive the seals in squarely with a large washer and long socket. Or anything that will get the seals installed flush and straight.
1981 Yamaha QT50: Yamaha 60cc hop up, PW gears, stock pilot, 75 main, red Uni filter, BP7HS plug.
2006 Honda ST1300
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