08-22-2017, 03:27 AM
(08-22-2017, 03:04 AM)The ferret_imp Wrote: 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.
100% agree with you the Ferret. I was on a ride this sunday where i was all over the motor in 2nd 3rd and 4th (after regearing only the top of 4th hits the governor) and it was amazingly fun and i was keepign up with much faster bikes with no issues (you can only go so fast on the road and the cb1100 keeps up in that range with most everything else), and im like 260 so probably one of the heavier riders. Since the motor is overbuilt ill be able to ride it like a bat outta he** for years and years and it will ask for seconds. a great ride to be sure.
The hassle of trying to build the motor for more power (other than bolt on stuff) is the heat as the Ferret said. I could see bumping it slightly and the motor would probably hold but then youd be needing to change the synthetic oil more often because of higher heat murdering the magic lube. I would still love to get a legit oil temp gauge setup so i know whats normal and if when im on the motor harder i can adjust the oil change intervals as needed. I religiously use the oil temp gauge in my cars and value its data. now to find a place to tap one in.