1 point of compression makes very little difference in power (9:5 to 10:5) As said whatever gain you "Theoritically you Might get" sometimes has to be tuned out so it does not detonate running gasoline. Anyone who has Desktop Dyno sym software can prove this to you.

10:1 is about the safe limit on gasoline, I do not care what engine it is, gas quality sucks today period! Engines can infact have inaudible detonation to the ear. And it plays hell on Rod bearings overtime!

That all said from 10:1 to 10:5 is just not a wise gamble. Some might get away with it others will not, and have major headaches. The reasons is a long list including cam selection. Point is what are people chasing every last tiny bit of performanace with a half point of compression at the risk of detonation? Not a good trade off in my mind.

As for the 211s I run them. They are strong in a 96 Inch!

 

The single biggest problem you can run into with 10.5:1 compression is not getting the timing correct. The higher compression, you may need to take out timing when running a base map download. Most maps used for a baseline load are standard compression.

 

I am running 10.5:1 compression. I haven't had any pinging at all. I use the highest octane available when I fill up. Sometimes that's 93 and sometimes that's 87.

I gained 10hp and 10tq over the street legal 103" kit. The only con so far after 3,000 miles is that the higher compression motor likes to cruise at a slightly higher rpm than it used to. I used to feel strong in 6th gear at 2600 to 2700 rpms. That was around 70mph. Now the bike likes to cruise at 3,000 rpms which means I am in 5th gear most of the time. 3,000 rpms is just over 80mph in 6th gear and I usually don't cruise that fast for any distance anymore unless I am on the interstate.

Dennis

 

I'm running stronger with a 10.5:1 96" than any 103s out there unless they've had head and cams. And as stong as alot of those. I take the bike to a Thunder-Max tuner on Thursday to get the timing tuned in. I agree if you don't know what you're doing, don't play around with a $20000 bike's engine.

The fact remains, done right, a higher compression engine (within reason) will perform stronger than a standard compression engine with the same set-up. Unless of course you're running a turbo. A 10.5:1 set-up correctly can and is a very reliable way to gain performance at a reasonable price. The Magic is to get these engines to breath better. Adding displacement is not where true performance gains are made. I see too many times, guys buy a bike and before they even ride it, they have a 103 kit done. They claim how much stronger it is, but really have no idea.

 

So got my tune done, 105hp and 113 tg. Bumping the compression up to 10.6 got me over 100 tq at 2500 rpm, about 1.5 secs sooner than before now I stay above 100 tq and 100 hp all the way to 6500 rpm. Before I would run out on top at 5k and didnt come on strong util about 2800 rpm. So the area under the torque curve is much broader now. No pinging but can alway get 92 or 93 octane fuel here in the midwest.