Head Mod (squish)
 

I drive a EC 300 '09 Model and I'm looking for bit more power at the bottom and a better throttle response since I mostly ride very tight and tricky stuff. I measured squish and my results are 2mm. The base gaskets are 1 grey and 2 greens = 1,1mm. Compression on a warm engine was 11,5 bar, 166psi. I know how to use a lathe so i was thinking to just take of 0,2mm off the head to drop the combustion chamber of the head down and therefor change squish to 1,8mm for starts and see if I like the results. The fuel we run here has at least 95 Octane so that should be ok. Will this mod be a risk for the engine or should I just go for it?

As long as you get cut the head level you'll be fine.

should be fine. might wanna check and see if piston lines up with exhaust port at bdc. you could just lose a base gasket or 2, if that still keeps piston in line with exhaust port. if not, cutting head would be the way to go. optimal is 1.2 - 1.6 depending on octane, port and ignition timing.... 1.6mm is a good number to shoot for. and you can still move it around slightly with base gaskets if need be.

Being a cheapskate I did mine by dropping the base gasket thickness, improved the bottom end but at the expense of top end.

I found exactly the same thing on my 250. I removed a .5 and a .3 gaskets from stock, leaving only a .1. The bottom end improved but at the noticable reduction in over-rev (top end). Because I rather like top end hit, I re-added a .3.

I took off the head today to look if the piston is aligned with the exhaust port at bdc. Looks like the piston is higher than the port. I didn't measure it but i can feel that the piston is higher when I go over the edge with my finger.

My 07 300 was that way. I went with the thickest and thinnest gaskets and had RB cut the head and do the carb mods. I ended up with exactly what I asked Ron for - slightly better bottom end and a top end that screamed like a 250.

I took off 0,4mm from the head and measured squish again. Now the 2mm solder barely gets touched, so I am at about 1,9-2,0mm. I checked compression and it went up from 11,5bar to 13bar. Is that too much already or can, should I do more??

13.5 is probably the limit for pump gas, higher than that and you will probably get detonation. Compression doesn't tell the whole story either, squish band and angle play a large part as well. So to go to a more desirable squish level you may have to have the head/squish band re shaped.

did you reshape the squish band or just cut the outer mating surface?


if you just cut the mating surface, i wouldn't go any further.

as you said previously, the piston is higher than the port, so now you can adjust base gaskets, and you'll be right where you want to be... try removing 1 .15 or .30 base and see what that gets you. you need to watch your compression. over 190psi can possibly ping unless race fuel mix is added...