Base gasket 'stack'

[WAZ]

I am getting ready to do a top end on my 02 EC300, including setting up cylinder height, squish and compression. My question is this: What base gaskets are typicaly required to set the piston at the bottom edge of the exhaust port? The top end gasket set from 'The motocross center' contains 0.5, 0.3 and 0.15 gaskets, but am unsure if I should order any extras just in case. Obviously there are variations in cylinder/port height and piston height, but a rough idea would be good.
Thanks.

[Zman]

Check out this other post. http://www.gasgasrider.org/forum/showthread.php?t=17578
The piston being at the bottom of the cylinder is not the most important issue. The port timing is more critical. Your first move is to determine how you want to change the power delivery from your engine. If you want to move the power from the low rpms to the high rpms then raise the cylinder with more gaskets. If you want more low end at the expense of the high rpm then drop the cylinder with thinner gaskets. If you just want more power all over, then cut the head and raise compression.

To answer your original question, I am not wild about stacking many gaskets so I would reccomend that you can cut your own thicker gasket from sheet gasket stock that you can get from most autoparts stores.

[WAZ]

Originally Posted by Zman

Check out this other post. http://www.gasgasrider.org/forum/showthread.php?t=17578
The piston being at the bottom of the cylinder is not the most important issue. The port timing is more critical. Your first move is to determine how you want to change the power delivery from your engine. If you want to move the power from the low rpms to the high rpms then raise the cylinder with more gaskets. If you want more low end at the expense of the high rpm then drop the cylinder with thinner gaskets. If you just want more power all over, then cut the head and raise compression.

To answer your original question, I am not wild about stacking many gaskets so I would reccomend that you can cut your own thicker gasket from sheet gasket stock that you can get from most autoparts stores.

I'm well aware of the theoretical effects of raising or lowering a 2 stroke cylinder as I'm sure you are too, but that isn't the question I asked.

If anybody has the answer to the actual question I asked, it would be most appreciated. Thanks.

[pscook]

I would be surprised if there is a "standard" stack that would provide that condition, especially since there is a variation of up to 0.5mm difference in squish between bikes, even in the same model year. Of course, the differing squish dimensions could be because of the differing base gasket stack ups.

What was your original BDC measurement and gasket stack height? I would then provide a quick answer of "the difference between those two dimensions" would provide the condition you are looking for.

You could also install the cylinder over the piston (without rings) and measure the difference, as I did, and install the gaskets you want to get to the dimension you want.

Good luck, and maybe there is a standard gasket stack that will give you the answer, but I am not sure if it is out there.

[motopsycho87]

I'm running 3x 1.5mm and turned about 1.8mm off my head for squish, then removed 7cc for compression. If you don't have those facilities, use the gaskets to get yournsquish right, worry about port timing later.

[JP4]

My stock base gasket stack was somewhere between 0.045" (1.143mm) and 0.050" (1.27mm) - it was a little hard to get a perfect measurement.

I used all the gaskets in the kit I got from Motocross Center (2 green ones with a thin clear plastic one sandwiched between them). The whole stack measured out at 0.035" (0.889mm). Worked fine, but I did have to go up a pilot jet as the thinner stack seemed to lean out the jetting.

[Zman]

I have a 01 XC250 that took 1/16 inch (1.5mm) to get it correct, which is why I cut my own base gasket from Felpro sheet gasket stock.

[lonetree]

ive had a 04 and two 09's they all have had a "standard" stack of 1.3mm-2x .5 and a .3 in the middle.