I want to shorten the compression height, and machine some valve pockets into a piston, and I can't figure out a good way to clamp the damn thing down without damaging it. Anybody done this before?

Background: I'm a low budget guy so I'm not going out to buy an expensive fixture. The OEM replacements are discontinued from Yamaha... its old.

Would I be able to modify a regular piston ring clamp to work out?

 

Ok, so I guess I'm going to glue some sandpaper down to a sheet of glass. Watch some TV while I slo o o o owly grind down the compression height of this thing.

 

well...make a block of aluming, and machine a hole in it so the piston fits in it snug...like .010 clearance I guess...maybe less and then put a pin thru where the wrist pin goes to keep it from spinning and make sure it fits tight as hell. and then knock yourself out.

Note I'm not a machinist, but I did stay at a holiday inn last night.

 

I was thinking of trying something like that with wood. I picked up the piston for ten bucks, no way I'm going out to buy an expensive block of aluminum to do this...

 

get a DA sander and go to down....and a die grinder while you're at it.

 

you should just be able to hold it in a milling vice on the flat sides, but get some plastic shim and use it between the jaws and the piston so you dont marr or deform it. then snug it up good and go to town. the piston should hold up fine, take light cuts if you are scared

 

http://www.bhjinc.com/1products/0-landing.htm
Click on piston tooling on the left.These are not cheap but it may give you some ideas.
Glenn

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 4drsedaneg &raquo;</TD></TR><TR><TD CLASS="quote">you should just be able to hold it in a milling vice on the flat sides,

the piston should hold up fine, take light cuts if you are scared</TD></TR></TABLE>

I just clamped it right in the lathe ghetto style. No shims. Spun it up, cut the skirt down, and then cut a few mm off of the dished top. Barely scratched it any. I sanded the scratches down and it looks like it will work out fine.

I'm going to do the valve reliefs by hand. They are 90 degrees from the old ones I cut off...

Thanks for the replies.