Big bore kit 63mm for GY6. How to make a bigger hole in the blocks without take a part engine!

DIY tool for making a bigger hole in the blocks of engine (125ccm GY6). Without take apart engine and remove of crank shaft.

[josepeixoto]

i dd it like you did, just no nylon bushing on the square steel plate, it is justa oome shot deal, and i did it with a steel hole saw;from 125 to 171cc; but the saw cut a 1mm groove on the crank round balancer, so, steel chips got inside;har a hard time fishing them out with magnets; changed oil and cleaned the screen a few times seems ok, i will drive it on the street, soon; so far it has been tested for around 2 miles, runs good
The big problem is that i reused the 125cc head and now the compression is huge and the starter has a very hard time turning over (it does at the 2nd or 3rd try, and it starts immediately) and the kick starter is impossible to get down against the compression, even if i totally stand on it, it takes 15 to 30 secs to go down
a sandwich plate 0.75 or 050 mm thick, i will do the calculations, with 2 gaskets, i should have installed on the bottom of the cylinder, may still have to do that if i don't find another way;
that or installing 3 or 4 head gaskets, need to calculate that too
that why the seller stated that the 125cc head could not be re-used

[rubensgarnier]

How do I know if the head bolts are going to fit?

[Peckadelic]

How did you clean the metal shavings out? I attempted something similar and my crank bearings are now destroyed after a very short time running it. I filled the jug to the brim with oil & turned the engine a few times like 10 times.

[sickssix]

no music please, if you insist on music, something soothing and pleasant not that loud rubbish,