XB12R Rebuilding Story and Customization

[Warlock]

I thought the pistons were the exact same. Only difference was the stroke.

 

[Thorivola]

XB9 pistons are dome topped and XB12 pistons are almost flat (very small dome)

XB9 is somewhere between 11.5 and 12.0 CR versus the stock 10.0 or whatever

so far below 4500 RPMs I've had no pre-combustion and it's been smooth as silk with a hell of a grunt

picture of XB9 pistons:

the XB12 pistons have a much smaller hump

compression ratio is a geometry measurement
basically, the amount of volume at complete bottom on the down stroke over the volume at top-dead-center up stroke

since all Buell motorcycles have a 10.0:1 ratio, with a small stroke length (the XB9) you need a small final area at the top of the up stroke

so by doming the piston, the piston leaves less room between the head and the piston surface

the picture I have here are 11.5:0 race pistons

they have thicker heavier tops and inside the piston skirt has a much different profiling to make them more durable to all kinds of combustion abuse

the pistons I actually ended up using were directly out of an XB9, the higher compression ratio gives you more torque but not really anything in horsepower

 

[tarvis]

cool thread cant wait to see a video

 

[kokomochandler]

so your picture is race pistons, is that what you used or did you put factory xb9 in. did it have any running issues ? my engine is on the bench and id love to try it and get my heads coated and put in a gold oil pump gear.

 

[browland]

man I am really thinkin about this I already emailed revolution performance about one of their big bore performance packages but if I could swap to the 9 pistons and have a noticeable diff it would save a small fortune

 

[kokomochandler]

does this affect the igniton timing at all ?

 

[Thorivola]

the last line of my last post says:
"the pistons I actually ended up using were directly out of an XB9, the higher compression ratio gives you more torque but not really anything in horsepower"

I made no adjustments in timing, because the only change is how much pressure the gasses are under

as long as the temperature and pressure isn't high enough it makes the gasses ignite any faster, there is no reason to retard the timing (which is what you would do to compensate for its willingness to ignite)

so basically, as long as you are running fuel with a high enough octane rating you aren't on the edge of pre-combustion you'll be fine to leave timing as it is

I also made no alterations to my ECM or anything like that

I'm running a complete buell factory race set: muffler, filter, ECM

if you want the cheapest strong performance upgrade, pull your cylinder heads off and contact these guys: http://www.jdeesperformance.com/

with the port profiling they do and XB9 pistons you can put down over 100 HP at the rear wheel and a hearty torque boost, not sure what numbers you get at the crank

I know a couple people with that specific set up, it's the simplest way to keep everything stock and get a nice boost

I didn't get my heads ported, I ran out of time

please keep in mind if you get a big-bore kit and stuff like that, you have to get head work done, get different cam profile, and do a bunch of tuning to really reach the performance level the equipment is capable of

if you have that much money to burn and all the free time for it, go ahead

I personally don't think screwing around with those extremes in engine characteristics is worth the time and money, just go buy an XBRR bike

 

[browland]

The Rev performance package includes the head work cams and other bits for right under 5k... almost like buying a second bike, I will be looking into jdees for sure

 

[Thorivola]

yea, I'd never put $5000 into a motorcycle I only paid $4500 for in the first place heh

 

[kokomochandler]

im going to give them a call and im definately going to be putting in the 9 pistons now. thanks for the info.

 

[Thorivola]

I'll let Jesse know I told you guys to contact him so he's expecting it

 

[kenney83]

What about the headers? I have heard of people swapping headers. I can't remember if it is 9 to 12, or 12 to 9. I believe they are a little different.

 

[Thorivola]

12 headers have a larger diameter than the 9 headers

people with XB9s can put the 12 headers on to get a little more airflow I guess, plus a muffler and some headwork could you give a substantial power boost with only map tuning

 

[GW 04 XB12R]

i have 9 headers on my 12. never got it dynoed, and it was like that when i got it so i can't tell you any differences... it definitely pulls hard, but then, don't all xb12's?

it has a k&n, jardine, and tune with the smaller headers. my theory is faster exhaust gases at lower RPMs, so more bottom-end torque, but it may lose a little top-end power due to the friction of the pipes and the large volume of exhaust gases. i'd love to do a comparison.

looks like i should get the 9 pistons, since i already have the headers!

 

[Thorivola]

the smaller headers will give you more back pressure, I don't have any idea what the performance would be like on an XB12 with XB9 headers

getting XB9 pistons won't change airflow during exhaust or intake strokes, just give you more grunt during combustion

here's a video:

 

[jzchev28]

good stuff right there, some interesting new ideas

 

[onelogue]

Thorivola, great video. Glad it finally came together.

Do you like the 9 pistons more than the 12's overall?

 

[jonzin]

Did the black powder coating have any impact on temperatures?

 

[Thorivola]

the bikes are powder-coated gray at the factory anyway, I just changed the color so I doubt it makes a difference but I hardly care to go through the work it would take to figure out if the color of the same material had a temperature difference lol

the XB9 pistons move the power-band right to idle, you can feel the extra torque as soon as you move the clutch

the bike will now take off without any throttle rotation if you ease the clutch in, and 1300 rpms is plenty good for a smooth easy launch

basically, I love the feel of the new pistons and you don't have to remap or anything to use them, they are a direct swap in in almost all cases

I've seen dynos with these pistons and simple head-porting that gives over 90 ft-lbs of torque and 100+ HP in the rear wheel hitting the ground

 

[epantell]

I know this is an old thread, but I'm about to put xb9 pistons in my xb12. Any regrets? Did you see a decrease in mileage? Any additional information would help. Thanks.