F5's 300 head mod thread

[Anders]

Thanks a lot for all the detailed info here. This thread is mainly about your 300 head, although you refer to your 200 as well.
I just measured my '15 200 squish to be 1.8mm (OEM setup, doing the bike's first ever piston replacement now).
I haven't removed the cylinder yet, but it sure has a thick base gasket, at least one of the 0.5 ones.
If I go with one .15mm gasket, that should bring the squish down in the 1.45 area, a tad too high I presume (if there is a 0.5 gasket now). However, I do have a lathe (and have cut heads earlier) so if necessary, I'll cut it down.

I thought about aiming for 1.3mm. Should I go lower? I run 98 octane gas (known as Super around here).
What squish height did you end up with on your 200? and what about the CR?

[(F5)]

I took one of the base gaskets out, bear in mind mine was the '02 200, then I skimmed it so squish was less than 1mm. 0.8mm would be ideal. 1.3 is miserable. Then cut chamber to reduce compression ratio.
13:1 should be fine, maybe up to 13.5.
You should check if squish band is parallel or tapered and correct to parallel. Can't remember thought the 200 wasn't bad in that respect but different piston manufacturers may be different as may changes over the years.

[Anders]

Originally Posted by (F5)

I took one of the base gaskets out, bear in mind mine was the '02 200, then I skimmed it so squish was less than 1mm. 0.8mm would be ideal. 1.3 is miserable. Then cut chamber to reduce compression ratio.
13:1 should be fine, maybe up to 13.5.
You should check if squish band is parallel or tapered and correct to parallel. Can't remember thought the 200 wasn't bad in that respect but different piston manufacturers may be different as may changes over the years.

On my '15 200, I found the OEM base gasket to be 1mm. The OEM volume above the piston is 15.2 - 15.5 ml (measured twice, got different results) which should give a CR of around 14:1. So I will aim for unaltered CR as this works well with my fuel.

[(F5)]

Take the time to get your eye in with measuring technique. Flywheel needs to be held at tdc which it doesn't naturally stay in. But yeah if it works with your gas keep it there.