| Author | Message | ||
     Loud_and_low |
I heard it was a relatively simple procedure to take my 9 and increase it to a 12. How true is this? What gains would I see? What I would be looking for is quicker out of the corners on the track and increased top speed. My 116mph takes a little while to wind up. Thanks in advance for your replies. | ||
| Dhays1775 |
I believe the easiest route to take would be a bigger bore via the cylinders. The 12 has a much longer stroke, therefore, you would have to split the cases and pull the crank, then put a 12 crank in it. As far as replacing the cylinders, the hardest part is just pulling the motor. The rest is pretty simple as long as you follow the steps in the repair manual. I kinda went the same route on my 12. I pulled the top end of the motor, removed the base gaskets, then installed a thinner head gasket. Bumped the compression a pretty good bit. If I had it in my budget for the larger jugs, I would have slapped them on. Whatever you decide to do, good luck and have fun!!! | ||
| Slaughter |
I'm prejudiced against the long stroke motors. I think the bolt-on 1050 kit is about right. A little more poop and quick-revving. boring out to 3 13/16 makes a helluva sweet engine but you GOTTA work with a machine shop that's done it before. Going to the 12 does mean a longer stroke as others have said. | ||
| Greg_e |
For racing you really want to stay with the shorter stroke. Keeping the shorter stroke and increasing the displacement means you will need to machine the cases to get above 1050cc, the 1050 kit is bolt on. Have you maximized the intake and exhaust with head work and a larger throttle body? what about cams and larger valves? on higher than 100 octane race fuel increasing the compression ratio is always good for more power but a little dangerous on street pump gas. If you really want more umph, then your money might be better spent on an 1125, you'll certainly spend most or all of it on engine work and never get the same amount of power that the slightly modded 1125 will give you. | ||
| Slaughter |
Greg is ABSOLUTELY correct. The air-cooled motor is extremely limited in terms of what you can do. I did the mods because it is a race bike in middle-weight twins classes. Big bore/short stroke = 1169cc (class limit is 1200) BUT - with heads, valves, cams, spigot bores, jugs - roller rockers and other stuff to painful to mention, you're going to have almost $5K into the engine and still only able to make about 105HP/78ft-lb If you're not actually racing, the power from an 1125 is far cheaper than the mods to the aircooled motor (but it is undeniably cool to be the "only kid on the block" with one of these motors) (Message edited by slaughter on June 08, 2011) | ||
| Loud_and_low |
Great advice. Thanks. Right now I have been doing track days the last 3 years on it. I am ready to take the next step and start the process to get involved in racing it. So, that is my main goal. I really don't know what all that entails, but am reading and learning. I don't really understand the classifications, or what the mechanical limitations for any class. So, this is my first part of the process. Getting the bike ready. Again, thanks for any opinions and information. | ||
| Greg_e |
Get the 1125, spend some money on one of the race schools since many of them will go over the prep work needed for your bike. Lots of safety wire which means lots of drilling. | ||
| Loud_and_low |
Yeah...but I LOVE my XB. I dig the simplicity. Can it not compete in it's allotted class? | ||
| Slaughter |
Check your race organization. You are likely to find that you can enter more classes on the XB than the 1125 although in either case, you're really only competitive generally in middleweight twins (XB) and heavyweight twins (1125) - every organization's rules and class definitions run a little different. |
