What size domes for 100 octane

[JoeHazzard]

I'm thinking of switching up my dome size. I have the Athena BB kit w/68mm pistons and stock stroke. I'm not sure what size domes they came with because it didn't say on them what they were. Which is kinda gaytarded. But the compression is suppose to be 11.9:1 and should run 96 octane. I usally mix 2 gallons 110 and 3 gallons of 93 = about 100. So if I'm already running 100 I was considering running 1cc smaller to fully utalize the octane or go slighty bigger to run 93. The bike runs strong now but had a coolant leak from a bad o-ring and not sure if it was caused by a slight ding on the dome itself which could have ate the o-ring. New domes would take in out of the equation. So if it eats this o-ring I'm getting new domes.

[AKheathen]

I'm thinking of switching up my dome size. I have the Athena BB kit w/68mm pistons and stock stroke. I'm not sure what size domes they came with because it didn't say on them what they were. Which is kinda gaytarded. But the compression is suppose to be 11.9:1 and should run 96 octane. I usally mix 2 gallons 110 and 3 gallons of 93 = about 100. So if I'm already running 100 I was considering running 1cc smaller to fully utalize the octane or go slighty bigger to run 93. The bike runs strong now but had a coolant leak from a bad o-ring and not sure if it was caused by a slight ding on the dome itself which could have ate the o-ring. New domes would take in out of the equation. So if it eats this o-ring I'm getting new domes.

the domes should have the size printed right on the side of them. your elevation will change that, too. i think you need 24cc to run 93, ideally.

[JoeHazzard]

the domes should have the size printed right on the side of them. your elevation will change that, too. i think you need 24cc to run 93, ideally.

 

 

Thanks AKheathen,

They should have been printed on them. But they were not. I decided I will go smaller if I do anything. I can't stand the idea of detuning. So if what your saying is true the Athena domes should be around 23 to 21. So I'll probaly go with 20 to 18cc domes. Does anyone know if any other companys big bore domes will fit the Athena head?

Edited August 14, 2010 by JoeHazzard

[firebanshee]

I would not go any smaller than a 20cc dome on a 68mil bore at sea level.

[AKheathen]

someone probably knows off hand, but you can just cc the domes yourself, or have them cc'd at a shop. use a peice of plexiglass and drill a hole in the middle. istall the sparkplug in a dome, turn it upside down, smear some vaseline or something around the oring area and put the plexi over the dome. use a syringe and measure how many cc's of water it takes to fill it. 18cc's would be murder on a big bore.

[misterww225]

To measure the cc volume, lightly grease the cylinder to effectively "seal" it, then rotate and lock the the crank at TDC. Wipe the excessive grease off. Install the head/dome and fill the dome to the bottom of the plug threads using the syringe with oil to measure the head volume. Be sure to remove the head and clean the grease off afterwards.