I guess I'm going 88" next year

[Phelan]

Just picked these up. Big Bore XB race cases with a billet trap door to boot. Windage tray has been welded, but otherwise they look sound, other than needing CLR bad. I don't trust the cylinder studs either, but for $200, not gonna complain. Actually there were 2 sets for sale, and my client picked up both, one set for me and one set for his future Lightning build.

http://www.ebay.com/itm/Buell-XB-Rac...-/161892491482

[RaisinCain]

Please post up when you get to building

[Phelan]

Of course! I'm excited. I said I'd do an 88', but it's still tempting to do a high revving 1204 with a 3.875" bore and 3 1/8" stroke (XB9 crank). Who knows. My client's bike will be either an 1170cc or a 1204, both options utilizing an 08 XB9 crank. I may duplicate it for simplicity, but not sure yet. It won't be til next year anyway.

[Chicknstripn]

For those of us that don't build engines for a living, could you give us the pros and cons to the type of set up you're looking to run? How high does a 1204 with an xb9 crank rev compared to say a bike with 1250 kit? And how much more power is achievable/available because of the difference in crank set up? I know theres no black and white answer here, I believe the effeminacy of the heads plays a huge roll in the power numbers, but just a general idea for us laypeople would be appreciated.
Does the increase in revs decrease the life expectancy of the motor? Or does the larger crank pin and lighter rods of the 08+ crank compensate for the extra strain on the motor?
And tuning... ....this going to be an EFI engine or a carborated build?
For some of us this type of build and info is like porn!
Thanks for sharing you ideas/build with us. Sounds very exciting and interesting.

[Phelan]

Using an 08 crank helps with the revs, and I plan on having the crank balanced to the pistons I use. A 1250 kit uses an XB12 crank (3 13/16" stroke), otherwise it's a 1050 kit on a 9 crank (actually 1021cc). Both are 3.563" bore. A 1250 with balanced 08 crank and forged pistons can safely be revved to 7400-7500 or so, with variance depending on piston design, whereas an 88/90" (3.813"/3.875" bore with 12 crank) shouldn't be rev'd over 7200 in the same scenario, due to much more piston mass and much shorter piston skirts, which creates more piston rock. A 9 crank has shorter stroke and longer rods though, so you can use pistons with full length skirts. Since the shorter stroke allows more RPM to net the same piston speed, a 3.563" bore 1021cc XB9 with pistons and crank balanced to each other can safely be revved to 8200 or so. A 3.813" or 3.875" bore XB9 with balanced pistons and crank shouldn't be revved over 7500 with the standard short skirt pistons supplied in most big bore kits. But I'm going to have custom pistons made with full skirts and short wrist pins, and balance everything in effort to run an 8200 RPM redline on the big bore XB9. Keep in mind my numbers are just ballpark, and other variables can affect these as well. For example, the teeth on the 08-up cranks create drag, so I'm specifically using an 03-07 style motor with a cam sensor so I can have the teeth cut off the crank when it's balanced (also for more cam selection).

[Phelan]

Oh, and it will stay DDFI, tuned with TunerPro RT.

[Phelan]

Tonight when I get back on my computer, I'll post up some info on my Uly motor builds. I've done two different 1250cc builds on the stock bottom end, with 2 different variants in the heads in the first build.

[Chicknstripn]

Man, I wish there was a shop near my area with your knowledge. The ECM tunning is the down fall to my build.
I knew the importance of balancing(crank and Pistons) but had no idea the difference in revs between an 9 vs 12 crank. Those higher reva give you a greater potential for HP correct?
I was told that lightening the crank diminishes the life expectancy of the motor. Is this true due to the higher revs?
And what are you planning on doing with your heads?

[Phelan]

Lightening the crank does diminish the life expectancy, because it allows faster revving, which creates more force and wear. I'm not looking to knife edge mine, just get them balanced properly for the pistons and get rid of the potential drag from the crank notches. All other things equal, the max power should be the same between an 3.813" bore XB12 or 3.813" XB9 build. The difference is that the XB12 will make the power and peak at earlier RPM, and thus making more torque. The main advantages of the XB9 builld are the potential longevity of bore integrity by using full length piston skirts (which won't fit with the XB12 stroke), usually somewhat faster revving, as well as the thrill of hearing a pushrod V-Twin scream at over 8,000 RPM.

As promised, a couple old build threads with some pictures.

http://www.badweatherbikers.com/buel...tml?1429569920

http://www.badweatherbikers.com/buel...tml?1436279887

http://www.badweatherbikers.com/buel...tml?1446426346

The best dyno I ever managed was with the setup in the middle link, I managed 103.51 RWHP with the stock exhaust, and 103.50 RWHP with a stainless Drummer. This was on a conservative dyno mind you, which showed 75.92 RWHP on this exact bike when it was stock. The current build, listed in the 3rd link, only has about 250 miles on it, and I still have some sorting to do, so I haven't dyno'd or tuned it yet.



Right now the bike is actually going through a complete transformation. New color scheme, wheels, bodywork, tail, non-Buell headlight assembly, etc. More to come soon.

[Chicknstripn]

You got 28hp by balancing the crank and tunning? No head work?
That's insane!
I haven't looked at those other build threads yet.
Very interesting stuff