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Post by reiko178 on Mar 3, 2011 0:12:08 GMT -5
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Post by speedy1125 on Mar 3, 2011 0:50:28 GMT -5
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Post by 90GTVert on Mar 3, 2011 0:59:01 GMT -5
:welcome:
The one you linked to is also a 139QMB engine, like speedy's. Do you have any particular performance goals, or do you just wanna tinker and learn?
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Post by speedy1125 on Mar 3, 2011 1:16:29 GMT -5
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Post by reiko178 on Mar 3, 2011 3:34:47 GMT -5
That is a great link wouldn't have thought to do all that but I will for sure. Just looking for something to mess around on and drive to work once in a while. I have a doodlebug minibike that I did a motor swap on and I just like small motors
I'd like to do a big bore kit But I don't k ow what I would do with the gearing since I don't quite understand how the auto tranny works yet. Need to do some more reading
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Post by Goosey on Mar 3, 2011 7:35:59 GMT -5
That would be a 4 stroke, GY6 engine. Common in most 50cc scooters and ATV's (any brand name). Cheap scooter, parts available (online), and fairly cheap. Look up parts by using "GY6", rather than "scooter" when searching on ebay. If you prep it properly it'll be a good short commuter, and not too complicated to work on. Not as powerful as the 2t's that many here have. As with any Chinese scooter it'll be do it yourself (with help from nice scooter people like you have found here). The CVT is pretty easy to work on with the right tools. Tools required are not too complicated, impact wrench (emergency 12v works great) sockets, 8mm, 10mm, 12mm, set of screwdrivers, flywheel remover, rubber mallet  feeler guages for valve adjustments... |
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Post by reiko178 on Mar 4, 2011 1:20:45 GMT -5
A few questions about 2 stroke tuning...
What is port duration? Is this how tall the holes are in the cylinder wall? Bigger the port the longer the duration? More time=more air/fuel= more power?
Which port is which I know there's an exhaust port what is a boost port? Is there an intake port as well?
Are reeds in between the carb and the intake? I'm guessing they take the place of an intake valve as a four stroke would have?
Pipe tuning: what is pipe math? Can Somone explain the basic concept of this? What does it mean when a pipe "hits"? Is this like an optimal rpm in the power band when you get the most power?
Sorry for all the questions but I'm just trying to wrap my head around all this
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Post by Fox on Mar 4, 2011 5:08:58 GMT -5
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Post by 90GTVert on Mar 4, 2011 8:21:08 GMT -5
What is port duration? Is this how tall the holes are in the cylinder wall? Bigger the port the longer the duration? More time=more air/fuel= more power? Basically. The port height, and port height relative to the cylinder wall will affect duration. Less duration tends to create more power at lower revs. Longer duration tends to create more power at higher revs and usually more peak power. Which port is which I know there's an exhaust port what is a boost port? Is there an intake port as well? The exhaust port is obviously the easiest to identify. It is generally the largest of the ports and the dead giveaway is that the exhaust pipe attaches to the other end of it. The boost port is directly opposite of the exhaust ports. The other ports are transfer ports. Basically you have an exhaust port (or ports in some cases) and the rest are intake ports. Are reeds in between the carb and the intake? I'm guessing they take the place of an intake valve as a four stroke would have? Carb>Intake>Reeds>Crankcase They are an intake valve/check valve, though the piston really does the work of the 4T valvetrain. The reed valve controls air/fuel entering the crankcases. The piston opens and closes the ports to allow mixture or gases in or out of the cylinder. Pipe tuning: what is pipe math? Can Somone explain the basic concept of this? What does it mean when a pipe "hits"? Is this like an optimal rpm in the power band when you get the most power? 2T pipe builders need to do a lot of math because they are trying to crate a pipe that creates peak power at a certain RPM. They need to calculate the tuned length of the pipe so that pressure waves reach their targets at the proper times. It won't do any good to have vacuum wave reaching the exhaust port to help draw fresh charge into the cylinder if that vacuum wave reaches after the piston has gone back up and covered the exhaust port for example. There's quite a lot involved, like angles of cones and how long each part is, diameters, etc... Here's a good animation w/explanations of the process... www.bukupower.com/AnimateCorrect.htmlMore info : 49ccscoot.proboards.com/index.cgi?board=basicstuff&action=display&thread=34749ccscoot.proboards.com/index.cgi?action=display&board=basicstuff&thread=343&page=1 |
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Post by Goosey on Mar 4, 2011 8:58:26 GMT -5
That price is only $200 more than a new 150cc engine  oops missed the shipping charge. |
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feeler guages for valve adjustments...
