hybrid chinese motors and performance tuning
- Thread starter foureasy
- Start date
as requested
YouTube - 0206001552.avi
sorry about the cell phone video, on my return trip from florida my camera and video camera were stolen at the airport
YouTube - 0206001552.avi
sorry about the cell phone video, on my return trip from florida my camera and video camera were stolen at the airport
These china saga rocks!!
Give me Fuel Give Fire Give That Which I Desire!! Just saying..
Give me Fuel Give Fire Give That Which I Desire!! Just saying..
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Some of the water-cooled pocket bike 49cc motors put out 12hp, my Kawasaki kx80 which is only 15cc bigger puts out 20hp. 6hp is not that amazing for the displacement.... go for 10! 
So what is the stock HP?
Honestly i don't know.
I only go by what they specify on the zoom site for the PK80.
Honestly i don't know.
I only go by what they specify on the zoom site for the PK80.
a kx 80 makes no more than 20 at the crank 10%loss to the wheel i know this because i had a kx 100 and it made 17 at the rear wheel on a dynojet 250I and my cr 250r has 42.9 at the rear wheel the stage 3 motor we are working on has tecnology the worl has not even yet seen
you would have a job making a chinese bicycle engine go any where near as hard as a jap bike .the jap 2 strokes all have some sort of exhaust valve ,the yamaha was the simplest a barrel with a piece cut out of it that rotates depending on revs ,its used to raise and lower the exhaust port to give more top end power. if you port the life out of a chinese engine you shift the power band towards the top end and loose all the bottom end power and end up with a razer thin power band . i tried to fit a garelli 50 cc barrel to the chinese bottom end but you would have to weld up and re drill the stud holes , they are off by a little bit, you could use the 6 mm studs but i like to do things properly .ill try and get a port map and publish the 2 port maps so you can see the difference.the garelli run huge 13 to 1 compression so when you go to kickstart it you think its seized , its got a UB20S delorto carby ,and the exhaust header pipe is also huge at around 30 mm outside diameter.i guess thats why the early garelli has a claimed 8 to 11 hp . so 6 + hp out of a chinese engine should be possable ,the guy with dyno tuned 5+ hp at the back wheel would already be making more than 6hp at the crank .
I just raised the exhaust port on my generic 66 jug 2.5mm and widened it 3.5mm. Kept the stock floor height, and general shape. Finished with 600grit. Not quite like Rich's finish, but smooth. Widened the intake about 3mm, and it is about 1.5mm taller overall, as I had to re-champher (cham-fer?) the whole perimeter of it. But I got to starin' and head-scratchin' and, having read a book or two on the subject, decided to screw with the tranfer ports. Firt order of bidness was to get my dremel all the way in to the port (Pencil-type/ cable attachment). Went ahead and looked at my CR250 jug for ideas. A dimmly lit light bulb went off somewhere above me, and I began cutting 10mm additional material from the bottom of the jug, under the transfers, keeping the same basic shape.
... Now I can access the whole port. The idea is to direct flow not to the back of the chamber like stock, but to the middle, where the charge will collide, and likely get blown out the exhaust port, given the decreased blow-down time from the raised exhaust. Expansion pipe mandatory now. Having the fuel/air mix aimed towards the center is the current way of thought to boost mid-range power, which I'll need, since I've likely destroyed all my low-end torque. So I ground the transfer shape to the limit of material thickness until my inexperienced mind was satisfied. I think I have created a dog of a motor. I made a total of six measurments and did zero math. This is not how you are supposed to port a motor, but whateva I do wat I want. Tommorow is the install, and wed. is the test run. Pics are-a-commin. Any knowlegeable advice is appreciated.
