How to cut piston Windows.

[chris2470]

Does anybody know the best or safest way possible to cut some windows into a piston. I've also seen many types, from 2 oval or round holes to a single hole, any advice on this will also be greatly received, thank you.

[dapper]

Largest angle grinder you can find

[camel]

well the previous comment is helpfull isnt it!!!
depends what facillities you have....if you know the exact position and shape you require,the easiest way would be to mill it out on a milling machine,if you havnt got access or a suitable mate to do this id start by drilling a hole and shaping it with a file to your dimesions,being soft alloy metal can be removed easily
remember if you do clamp the piston in a vice to use something not to mark the piston,some cardboard will do and definatly do not clamp it to hard to distort the shape.

[ducksta]

i know how to put a hole in the top of the piston if thats any good to you :anbrgin;

[wack 63]

Mark out the windows then drill a hole bit enough to get a small dremil burr in the 4 corners(presuming square shaped) and cut the window out a few mm inside your marks then carefully square them up with a radius in each corner.I hold the piston top to bottom in a vice with soft jaws and work from above.

[tavspeed]

before you go down the route of cutting windows in your piston,which could weaken the piston substantially,you can get similar results by cutting the piston from the gudgeon pin to the skirt,havent seen one done like this,perhaps somebody has more info or pictures of how to do it.

[ulyssescale]

I use a Proxxon rotary grinder with a carbide bur. Drill a small starter hole and then rout it out slowly.

This is me doing an Imola piston for Mugello 186:

Adding windows to Mugello piston by SFvsr, on Flickr


Mugello piston finished by SFvsr, on Flickr

I also did some windows on a MB RaceTour piston destined for an LTH Reed Manifold on GP barrel:

Modified Lambretta Piston by SFvsr, on Flickr

[gaz_powell]

hi

i`ve just done a TS185 for a T5 polini barrel:-

1. masking taped the whole piston and marked the port out
2. stitched drilled the hole roughly and popped out the piece
3. filed it to correct size using a fine file
4. rounded the corners and took the sharp edges off

also had to shorten the skirt :-

1. measure the amount to be removed from the skirt
2. put piston in barrel with the area to be cut off poking out the bottom
3. line up cut mark with bottom of barrel and clamp - this ensures a perfect cut around the piston as the base of the barrel is the guide for cutting
4. chamfer the cut with a file

best of luck

[Starwave]

Hello

Not having a lot of kit in my garage I drilled 4 x 12mm diameter holes in a 225 Asso piston, when I fitted an LTH reedvalve. This was done using a normal household leccy drill. I filled the edges a wee bit and went over them with a bit of wet n dry. As long as there are no sharp corners or edges I reckon the shape of the holes is immaterial.
The holes are positioned horizontally so the outer edge of the holes are a few mil in from the edge of the inlet port. This leaves a decent amount of meat between the holes. The vertical position of the holes were drilled so the inlet port is never blocked (although the scoot won't induct fuel mixture for the full stroke of course). The top holes are quite high up but I think I read that can aid cooling of the piston crown, although I may have made that up. And it's bowlacks.

Anyhow, I've used this piston for about 4000 hassle free miles in a Rapido 225 LTH reed set up and am well happy with the results. Could put in a boost port sometime as the positions of both the ring pegs and the holes would allow this.
I tried my butchery out on an old knackered piston first and would upload a pic but I cannae figure out how.

cheers