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?
Head Mod (squish)
- Thread starter Madhead
- Start date
stainlesscycle
Site Sponsor
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.
wasp4banger
New member
Being a cheapskate I did mine by dropping the base gasket thickness, improved the bottom end but at the expense of top end.
bchatt
Bronze Level Site Supporter
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.
gasser
New member
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.
noobi
New member
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.
stainlesscycle
Site Sponsor
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...
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I didn't reshape the squish band. Just cut the mating surface. But I just came back from a test ride. And it seems she's got a lot more torque and snap than before. Topend is still ok for me since I ride more tight technical stuff. And on the street she just hit 140km/h with a 13/51 chain ratio. So for now I'm happy and I think I will leave it this way, because I don't know how to reshape the squish band. Or do I just have to change the angle of the band? If I take out an 0.3mm gasket I would be at 1,6-1,7mm squish but wouldn't that raise my piston even more compared to the exhaust port at bdc?! and I would loose more top power right?
stainlesscycle
Site Sponsor
sorry, i wasn't thinking. if you remove base gaskets your piston will be too high into the exhaust port most likely.
GMP
Active member
Squish is adjusted to be consistant across the width of the band by cutting the head so that the desired squish is met at the inside edge (the largest usually). Then the band is cut back at an angle so that the outside edge matches. This is what the solder sample is for, to get the angle right. The bowl is then scooped out to drop compression to the desired level.
Its all about effective squish. You can have a very wide squish band, which is theoretically good for low end, but if its only tight over a short distance then it doesn't matter. My heads that Ron did actually came back a mm more narrow, but totally consistant, so much more effective squish.
Its all about effective squish. You can have a very wide squish band, which is theoretically good for low end, but if its only tight over a short distance then it doesn't matter. My heads that Ron did actually came back a mm more narrow, but totally consistant, so much more effective squish.
stainlesscycle
Site Sponsor
squish band also is dictated by bore diameter, and piston dome profile. so when you send a head out to rb, you are getting a bit of work for a relatively cheap price....
bchatt
Bronze Level Site Supporter
Are the piston dome profiles always exactly the same? What say you replace a piston with a different brand - will the dome be the same? Would you need to re-measure and perhaps re machine the head?
A while ago I replaced the stock (which happened to be an S3) piston with a vertex. I forget the exact figures but there was a difference between the two, especially the distance between the top ring and the crown.
A while ago I replaced the stock (which happened to be an S3) piston with a vertex. I forget the exact figures but there was a difference between the two, especially the distance between the top ring and the crown.
stainlesscycle
Site Sponsor
not sure how ron is doing it, but to the best of my knowledge, the squish band volume has to be adjusted, so the band is displacing the proper amount versus the entire volume of head. i would assume the angle is kept the same (hence the solder - measure outer edge, and inside of band, and duplilcate original angle, while maintaining proper head volume) the jennings book goes into detail about squish band volume versus total head volume. not necessarily parallel with the piston dome... (if i remember correctly) the original squish band angle is not parallel with piston dome, it's tapered.
GMP
Active member
Head is milled to acheive the desired squish clearance at the GREATEST current point, always the inside.
Band is cut to keep this clearance consistant to the outside edge
Head volume is adjusted to reduce compression to desired level. Band width may be more narrow but consistant width gives more EFFECTIVE squish.
All based on compression/fuel, and original squish data (solder crush sample)provided.
Band is cut to keep this clearance consistant to the outside edge
Head volume is adjusted to reduce compression to desired level. Band width may be more narrow but consistant width gives more EFFECTIVE squish.
All based on compression/fuel, and original squish data (solder crush sample)provided.
