hybrid chinese motors and performance tuning

Getting a High comp engine to run without burning up in the AZ Desert is a lot different then up North. There is a huge temp difference.
 
Yes, and some of them are running special blowhards. I am not sure if they are the centrifugal or roots type.
 
each main bearing got an oil feed


holey piston. this is the stock chinese piston with large intake windows and lateral gas ports.


and its assembled




the cylinder has been decked 3mm for that perfect squish.
 
how do you think chinege pistion will live? and by the by i love the gass vents r you gunna run it with 1 ring then?
 
i cant imagine it will last too long. 1 ring yes. those vents dont go all the way through though. they cool the piston and clear the ring of exhaust gasses at the expense of a little primary compression.
 
and if you had the ports going all the way through youd leave the chance to hang a ring and detop the pist but you know 10000 rpm and a good bump might just do it for ya i wanna see :eek::eek::eek::p
 
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Hi foureasy, I love the amount of time and effort your putting into this, it's very fascinating. This thread opened up a whole new world of possibilities with moped and pocket bike motors and I now understand the interest in mopeds. I didn't know people were modding them. I have a few questions for you if you don't mind. Your clearly over taxing the strength of the of the bottom end and bearings of the motors. Isn't there any alternatives to the cheapo bottom ends these motors have? Wouldn't you be better off trying to get power at a lower rpm? Are you designing your own pipes? How the heck does the drive line hold up? Thank you, Brian
 
ruppster,
i think the cranks are ok for sub 10k rpm motors, they just need to be balanced and trued with good bearings installed. you know how your motor starts off smooth and gradually gets more vibration until you feel like the motor will come apart. it will! with a balanced crank the motor feels a lot like my panhead, there is a definite low rpm vibration, and as engine speeds increase, the motor gets smooth as butter.
i am designing and building my own pipes out of .023 stainless. my chambers weigh less than the stock pipes. my last pipe had a longer baffle cone for more over revs and it was letting me hit rpms slightly above 11k, which ate up some big end bearings. my next pipe will have a shorter baffle cone which will give me a higher peak power and act like a rev limiter, hopefully somewhere around 9500rpm. the only driveline failures i've had were with a bicycle chain as a drive chain. not only did it break, but it caused all kinds of vibrations.
 
Thanks for the info but now I have more questions. How did you figure out that moped stuff would work on these motors?You must have had some cross exposure to pocket bikes or mopeds or work with two strokes somehow, what else am I missing? Are you using pipe software? I'm surprised the crank assembly is good for that kind of rpm, putting the holes in for main bearing lubrication was a great idea but I can't believe it didn't have some from the factory. I just got my first motor a couple of weeks ago so I haven't been into one yet but they look about as hi tech as a weed whacker.
 
i had almost zero 2 stroke knowledge before i got one of these bikes. most of my experience is with welding and fabrication for custom cars and pre evo harleys. the only software i use is cone layout, and most of the rest of the info is here
chamerdesigndimentions.jpg


6202
 
finally in the frame. and a new intake for the flatslide.
upon looking at these photos now, i see that i need to slide the rear motor mount up on the seat tube at least an inch. that will give me more room to get the exhaust past the downtube without obstructing the flow. luckily the intake will still fit.

DSC01158.jpg
 
foureasy said:
all those nicks were from a previous wreck that broke the intake off and sucked some of 4th ave. into the chamber.
the head gasket (silicone) leaked and caused a major lean condition which ventillated my piston. the cylinder is fine, nikasil is very hardy. new piston ordered yesterday. i did some port work on the transfers also last night.


oh yeah, when i switched to the flatslide mikuni, i stuck with gas for now. 110 vp and klotz at 32:1
Click to expand...

awesome! I love Klotz! It's the only thing I would run in the dirtbikes, only two stroke oil I've bought since I was 14. Which Klotz do you use?
 
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