08-22-2017, 03:04 AM
Raising compression is not difficult, but it is difficult.... if you get my drift. There is no magic button, the motor must come out and get breathed upon by someone that knows what they are doing. If he said it would have been easy for HONDA to do, he is right, but that is not what Honda chose to do in designing this motor. If he said it would be easy for YOU to do, I am surprised.
In order to raise compression you have to decrease the space in which the gas compresses. That is usually done my milling the cylinder head (or using thinner head gaskets..or higher domed pistons) making the dome of the cylinder closer to the dome of the piston creating less space for detonation therefore upping the compression ratio. Make the gap too small however and the pistons slam into the valves when they are open. Don't mill it flat and you take the chance of creating a gap or leak of compression or oil. Personally I am mixed on this when it comes to streetable bikes and the CB1100 in particular. I certainly wouldn't want to do anything to my engine which would make more heat, which raising the compression ratio would do, however I think Honda has over built these motors and doubt a small increase in compression would hurt anything. You would also have to use an octane of gas more appropriate for a higher compression motor, which again produces more heat.
The thing for me is, this is such a lovely motor, with IMO the right power, right where it needs it, that I see little benefit and much risk from changing how Honda designed it. Unless you did intake work, exhaust work, cam work, valve work I can't see where just raising the compression would have very much effect. You are certainly not going to go from 88 hp to 104 hp (or whatever) thru just a boost in compression IMO. Performance is a chain and adding one link doesn't make your chain much longer... a bunch of new links are required to make the chain very long.
But that's my opinion.
A serious HP chaser may have an entirely different outlook and opinion.
In order to raise compression you have to decrease the space in which the gas compresses. That is usually done my milling the cylinder head (or using thinner head gaskets..or higher domed pistons) making the dome of the cylinder closer to the dome of the piston creating less space for detonation therefore upping the compression ratio. Make the gap too small however and the pistons slam into the valves when they are open. Don't mill it flat and you take the chance of creating a gap or leak of compression or oil. Personally I am mixed on this when it comes to streetable bikes and the CB1100 in particular. I certainly wouldn't want to do anything to my engine which would make more heat, which raising the compression ratio would do, however I think Honda has over built these motors and doubt a small increase in compression would hurt anything. You would also have to use an octane of gas more appropriate for a higher compression motor, which again produces more heat.
The thing for me is, this is such a lovely motor, with IMO the right power, right where it needs it, that I see little benefit and much risk from changing how Honda designed it. Unless you did intake work, exhaust work, cam work, valve work I can't see where just raising the compression would have very much effect. You are certainly not going to go from 88 hp to 104 hp (or whatever) thru just a boost in compression IMO. Performance is a chain and adding one link doesn't make your chain much longer... a bunch of new links are required to make the chain very long.
But that's my opinion.
A serious HP chaser may have an entirely different outlook and opinion.