YZ250E squish adjustment

[oldyzman]

Gday lads,
In the past when i have adj squish, i have had the fortune of being able to reduce the thickness of the base gasket. My yz is allready down to 0.5mm base gasket std.
The squish maesurement is currently at 2.0mm. I have read that this is excessive.
I am trying to achieve 1.2mm or so.
The head gasket is copper std and it would be hard to change the thickness.
The mateing surface on the head allready adjoins to the squish ring.
I can remove the studs to machine the top of the cylinder and possibly have to helicoil one or more to put them back in.
Or is it the done thing to use a lathe and grip the top of the cylinder inside of the bore in a three Jaw chuck and turn down the base face of the cylinder??


All coments welcome
Brett

[jimg1au]

brett
i thought that you welded up the head and machined out what you want.
i have a nos high comp elsinore head like chalk and cheese compaired to std
jim

[oldyzman]

Thanks Jim,
The head allready has a reasonable squish ring, the prob also is thet the piston sits 0.9mm below the cylinder face and once you add the gasket atapprox 1.0. this means the head squish ring starts off allready level with the head mateing face...
Brett

[JohnnyO]

Machining the top of the cylinder is probably the best way to do it. If you machine the base of the cylinder you are changing the port timing by lowering the ports.. which may not be a bad thing on a 250E, it would give you more bottom end.

[Taka 100]

i know when i used to bump compression for meth i bought thin copper sheet and cut out gasket with siccors and sharp punches and heat anealed them and never had an issue could be the go before the chop shop

[jimg1au]

brett
if you want to try to make your own we have the hole punches at work bring it over 1 night and we can punch the holes in
jim

[oldyzman]

Thanks Taka, Jim amd Johnny,
I think i will try to get some thin copper and try that port of call first as it is the least permanent ...
Brett