I did go from 11:1 to 14:1, and you can tell a big difference all the way through. Similar to 1BadRaptor, I got faster with the extra compression. I did change to a Grizzly 660 battery as well with the added compression. Makes starting easier. The YUASA Grizzly 660 battery was easy to get off Rockymountainatv.com and I haven't had a problem to date with my build. Going up on compression and running race fuel will call for a rejet. So don't forget that.

And goodluck with the high compression. I have a feeling you will love it. [img]i/expressions/face-icon-small-smile.gif[/img]

 

I installed the Grizz battery in my Rappy also and although it did help because the battery didn't go dead it still stressed the starter alot and starting was still hard.

 

Hey guys...........If your crank is balanced to an 11 to 1 piston and you install a heavier piston laterlike a 12, 13 or 14 to 1...will that not effect your balance?????[img]i/expressions/face-icon-small-confused.gif[/img]

 

After having my crank balenced for the Ross 11:1, I was informed by Falicon and Craycraft, that the 14:1 would not hurt anything.


And with my 14:1 set up, my start's are not hard. Three tap's of the throttle, and the push of the button and it fires right up. Knock on wood...I haven't had any trouble with the one way or anything since the build.

 

I don't think you should NEED to balance your crank, it's just another one of those options. It's always a good thing to have it balanced but nothing should go wrong if it isn't. I was running 12:1 on an unbalanced (stock) crank and it was fine but after the rod failed and tore my engine up I had to get it rebalanced and welded.

Yamaha660r: My rappy always starts up fast and easy but USUALLY when the piston first hits the compression stroke it stalls for a second before turning over again, after it hits that first compression stroke it always starts up on the next revolution.

 

I did the same setup as Sam here and from the 11:1 to the 12.5:1 it was a well noticeable increase!! Then I went to the 14:1 and it was exactly double the increase [img]i/expressions/face-icon-small-happy.gif[/img] You will notice the difference and with your new Rod, you will be safe. I ran VP 110 and it worked out great!!