help, scooter acting up By seanstr (Read 3,496 times)

[sprocket]

Do you know you need to have the engine case halves machined?? That BBK doesn't just slip in...it is a ton of work and expense.. just so you know...

[jct842]

some thing seems way wrong:
........................................................................ Re: help, scooter acting up
« Reply #50 on Mar 31, 2012, 8:50am »

Ordered big bore kit. Scooter Big Bore Kit 72cc GY6 QMB139 Four Stroke. 72cc GY6 QMB139 Four Stroke Big Bore Kit 72cc 47mm Increase Power by up to 30% and torque by up to 50% Each kit includes: Milled Cylinder Emissions style Head with 18mm intake 16mm exhaust and high performance springs Cylinder, piston, piston rings, piston pin, and clips Top end gaskets Performance Camshaft (not shown but is included) with 4.75mm intake stroke 4.55 exhaust and 123 degree lift angle. It has same emissions attachments mine has already too. I'm going I'll be ok putting this on. Tools needed?
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« Reply #59 Today at 5:28am »

Never done ring job. The bbk is supposed to be for the 150cc to whatever size a 63mm cylinder gives you. Just found out it's like a 178cc. That seems good.
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[roketafan]

63 machine case....

[seanstr]

What is involved in boring out case

[Alleyoop]

Here is a an example of MINE and I only have the 62mm kit yours the 63mm is a little bigger
than mine.
Now you side the size of the Original Pistion and the 62mm piston well that has to fit in what is called the JUG inbetween the 2 motor halves. So the hole in the motor case has to be made bigger to fit the Bigger Diameter JUG that carries the bigger pistion.
In other words you have to DRILL out a bigger hole that is what boreing is.
Alleyoop

[sprocket]

You need this done by a machine shop...because the tolerances are very very tight. Or invest in a case bore tool from NCY

www.mbe-motorsports.com/catalog/index.php/cPath/1_95

people have tried to do this with a dremel tool it doesn't work...

This video explains what you need to do

[seanstr]

Ok, big problem solved, I hope. I ordered the wrong size bbk. So, I'm returning it, & just getting a 150cc ring set. Should be gear soon. The thought & cost tobore out case, too much. Need to save $, not spend it.