Setting squish on a 02 MS4

[mahoneygod]

Just double checking the squish I should be shooting for is 1.00 mm?

[Speeddog]

That's the generally accepted number, yes.

[memper]

Squish? You mean sag?

[ducpainter]

Squish? You mean sag?

Nope...he means squish...

the distance between the piston and head at TDC.

[Speeddog]

Squish? You mean sag?

No, squish is the distance between the top of the piston and the bottom of the cylinder head at TDC.

[lazylightnin717]

Excuse my ignorance but how do you "set" that?

[ducpainter]

Excuse my ignorance but how do you "set" that?

Typically with base gasket thickness.

If things were past adjustable tolerances you could machine a surface.

[mahoneygod]

Speaking of base gasket thickness where does one acquire different thicknesses?

[Speeddog]

Cometic makes head and base gaskets, tho they don't show different thicknesses.


AFAIK, 916SBK base gaskets would be the same pattern, typically the SBK's had different thicknesses available from Ducati.

[mahoneygod]

When I replace the retaining clips for the pistons do I need a specific kind or will the ones from Lowes do the job?

[ducpainter]

When I replace the retaining clips for the pistons do I need a specific kind or will the ones from Lowes do the job?

I've never, and wouldn't, use clips from Lowes.

Get them from Ducati or whoever manufactured the pistons.

[bigiain]

Brad Black just blogged about setting squish - this was about a carbed 900, but it's probably worth a read none the less:

http://bradthebikeboy.blogspot.com.au/2012/05/setting-squish-and-cam-timing.html

big

[mahoneygod]

Good read. If my squish is good at 1.00mm do I need to advance my cams?

[Ddan]

Interesting read, but I'm curious about his comment that looser squish could lead to detonation.  Anyone got any insight?

[Speeddog]

Good read. If my squish is good at 1.00mm do I need to advance my cams?

You can degree your cams to Brad Black's specs:
http://www.bikeboy.org/camtime4v.html

Likely you'll need to adjust mixture a bit, so that may make a difference.

Interesting read, but I'm curious about his comment that looser squish could lead to detonation.  Anyone got any insight?

Narrower squish leads to more combustion chamber turbulence, so mixture is less likely to detonate.
And if it's narrow enough, the mixture there won't burn 'til well after TDC, as the piston and head absorb heat from the thin layer.

If it's wide, it takes a long time for the flame front to fill the combustion chamber and then get to the edge of the squish.
During that time, the pressure is rising, and it may get high enough for the mixture in the squish to ignite on it's own (detonation).