EC300 cylinder head
- Thread starter juuso*
- Start date
The free space between the head and piston (squish) varies from bike to bike.
You will have to measure the squish using this method...
http://www.gasgasrider.org/html/measuring_squish.html
You will have to measure the squish using this method...
http://www.gasgasrider.org/html/measuring_squish.html
Jakobi
Super Moderator
No fixed measurement, and even less chance of guessing with an unknown engine. Variables include cylinder height, base gasket stack, and the head itself. Changing any will effect the compression ratio (and the piston to head clearance aka squish height). Its essential that you measure it up.
Kind of on topic...
About to send my head off to get worked on. Quick question, I don't know what base gaskets I have currently. Going to throw some rings and new base gaskets in for the hell of it.
Where should I have the piston set up with the base gaskets? i.e. flush with top of cylinder at TDC as per KTM set up's or flush with exhaust port floor at BDC as I have read here somewhere?
Also should I set this prior to taking a squish measurement and sending the head off?
cheers.
About to send my head off to get worked on. Quick question, I don't know what base gaskets I have currently. Going to throw some rings and new base gaskets in for the hell of it.
Where should I have the piston set up with the base gaskets? i.e. flush with top of cylinder at TDC as per KTM set up's or flush with exhaust port floor at BDC as I have read here somewhere?
Also should I set this prior to taking a squish measurement and sending the head off?
cheers.
Jakobi
Super Moderator
The piston edge ideally should sit around the bottom of the exhaust port at bdc. Anywhere from flush to around 0.7mm above the port will be fine. Flush favours top end performance, while going the other way gives more grunt down low. Go too far and you'll lose top end. If you've been happy with the power curve you have currently just measure the gasket stack when you pull it down and use the same again.
Definitely measure the squish and have the head machined to suit the stack you are using. You can still measure squish first and then calculate the adjustments from there for the gaskets.
Definitely measure the squish and have the head machined to suit the stack you are using. You can still measure squish first and then calculate the adjustments from there for the gaskets.
Thanks. I'm not super happy with the top end so I may try and adjust the stack depending on what it currently is so the piston is flush with the exhaust port at BDC.
When I order the base gaskets what sizes should I get? ie what size usually gets the piston close to the port?
cheers.
When I order the base gaskets what sizes should I get? ie what size usually gets the piston close to the port?
cheers.
GMP
Active member
I think trying to get the piston even with the exhaust port is somewhat ineffective. At that point in time, its all over. Its the exhaust port roof and transfer port timing that make more difference. The corrected squish will help EVERYWHERE. I wouldn't sweat this too much as 300s don't rev out like the 250s anyway. I'd just set it up with a single .5mm or .5mm, .3mm for a slightly higher deck. Measure the squish as describe in the link and have it corrected along with compression. I would think your local tuner knows what works with your fuel. Also make sure your PV is opening completely. You can always retard the static timing slightly for more top end as well, free and completely reversable. 300s have a lot of room to play.
