2011 GG 300 SD squish, comp, and jetting data

[kahluablast99]

During my recent top end rebuild, I measured my squish to be 2.1mm at the outside edge and my compression at 125psi. So, I sent my head off to Ron and had him take it down to 1.1mm. I also tried to have Ron adjust the volume of the combustion chamber to raise my compression since the bike has never had higher than 130 psi even when new. (This is at 6,600 feet elevation so there's an expected loss of around 20% or approximately 30psi.) Unfortunately, when I got the head back, the squish was right on at 1.1mm but my compression stayed the same. Ron adjusted the volume of the cc to be around 16cc but I think at this elevation, I probably need to take it down to 13 to 14cc. I wonder if the other GG's of this vintage also have low compression from the factory. I was surprised to see how high SixDays compression was at 5,000 feet. Maybe GG fixed this problem on the newer bikes.

[Bikerdad450F]

I measured my 09 ec300 today and the .095"/ 2.41 mm solder I laid across the piston didn't even get touched. So I'm at work measuring up a piece of round stock so that I can machine the head my self. measure 3x then cut once, i suppose. I will have to see if my mandrel spins the head concentrically or not. the head seems pretty uniform, i was going to thread some rod to screw into the plug hole and see what it looks like from there.
btw. I didn't do a compression check first, so i'll bolt the head back on in am and do that first. got to have a baseline, I run 94 octane Chevron gas at 500 to 1500 ft. Pacific coast BC

[AZRickD]

Somebody has some increased horse power and torque in their future.

[Bikerdad450F]

2.74 mm of squish ! and while I was at it I took a compression reading. 135 psi. This is with a brass adapter on the gauge, it is bored out inside so I've noticed that my readings are about 10 psi lower than they would be when I don't use the adapter. I suppose the extra volume inside the brass adapter is effectivly increasing the measured combustion chamber volume. I also measured my gasket stack under the cylinder, it is 3 gaskets; 2 green .5 mm, and 1 gray ? .25 mm . 1.25 mm total, and all this cylinder raising and the ports are still not exactly lined up with the piston at bdc. it is about .5 mm from being flush. I intend to leave the gasket stack in place and just machine the head to 1.4 mm squish.

[Jakobi]

Still unsure about measuring it through the plug hole. Would rather do it properly which brings me to my next dodgy question - Is it ok to reuse the gasket for the flywheel cover? I've already ordered all my parts. Spose I can chase up one more if required.

I'll be pulling the bike down for a top end soon. At that point will check current squish and note gasket stack.

Will then lift jug to set ports flush with piston at BDC and measure squish stock, S3 silver, red, and black.

Is it okay to take compression readings without the head o-rings in before deciding on which is best squish and comp?

[gasgasman]

Measuring through the spark plug hole won't give a reliable reading due to the shape of the combustion chamber.
You can reuse the ignition cover gasket.
When you raise the cylinder to match the ports, you can use the black insert for the S3 head.
The head gaskets will have to be in place for the compression reading.

[gassi]

Originally Posted by Jakobi

Is it ok to reuse the gasket for the flywheel cover?

I put a little grease on the gasket's. Some place's you can reuse them many times and they seal better!

[Jakobi]

Thanks all.

I was intending on using the black insert but thought it would be helpful to record the measurements for all the inserts out of interest. Sounds like it'll be a pain if i have to seat the o-rings for each one.

I'll still probably measure up the squish using each insert and pick the one that gets me closest to 1.4mm

[gasgasman]

To measure the squish, you don't need the o-rings in place.
The o-rings are not spacers, so the won't affect the squish dimension.

The black insert is considered "very high" compression.
I'm figuring that with the cylinder raised, the squish will be brought back into spec.

[Jakobi]

Yes. I am aware I can measure squish without the o-rings, but I can't measure compression

Also aware lifting the jug for port timing will increase squish, and decrease compression, which should be brought back into spec by using the higher compression insert!

How much compression is too much?? I'm not racing this bike and reliability is heaps more important than performance.