| Author | Message | ||
     Shockeere |
Hello everyone, I think this is my first post on the Board. I ride an 07 xb12stt. This may be a long post.  I have a few questions for discussion with regards to raising the rev limit on my bike. I would like to bump it up +500 or even +1000 rpm, and do it properly. I believe there is a lot of power left on the table with our conservative rev limits. I have read many posts regarding jeopardizing durability, but i don't mind hearing more opinions on that aspect. I was inspired to look into this further by looking at this: http://www.sportrider.com/bikes/sportbike_dyno_charts/photo_17.html horsepower does not drop on any of the xb12 charts I have looked at. It only climbs linearly to red-line and shuts off. I believe that if we can extend our red-lines, our power will continue to grow in a linear fashion. I have ecmspy, and I noticed that the fuel map goes up to 8000rpm. However, the timing map only extends to 7000. I think that to safely scale up the rev limit, one needs to modify the timing map to have control over how the motor behaves at a higher limit. For reference, I attached some images of stock maps from an xb12 and an xb9. To start, I am considering a +500rpm increase. My scheme is to rescale the last column of the timing map to 7300, bump up all limits (soft-hi, soft-lo, kill-hi, etc) by 500, and to refuel the 6k, 7k, and 8k portions of the fuel map to run pretty rich just to be safe. I also adjusted the rear ignition timing map's final column to be more consistent. Most of my changes are reflected in the images below. My revised fuel map - prob needs more work  rev limits increased by 500  rescaled ignition timing map  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Stock map images for reference stock fuel map 900 front  stock fuel map 1200 front  stock timing map 900 front  stock timing map 1200 front  | ||
| Slaughter |
The problem is the valve train and the bottom end. UNLESS you've beefed up BOTH your valve train and big-end bearings, you can really be in for a world of hurt by spinning that much faster. You can get the bottom end Timken bearings put in - or even better, put the 2008 flywheels in there. Top end would be a little cheaper - roller rockers, possibly stiffer springs. What cams you running? To get comfortable with a reliable 8200 RPM rev limit, it cost me durn near $5000. | ||
| Slaughter |
I might add that after 36 races last year, I didn't have to do a thing to the bottom end during my December rebuild. | ||
| Glitch |
Don't listen to Slaughter. You can go 1000rpm above the red line, no sweat. I want first dibs on your suspension, and drive belts and pulleys. | ||
| Froggy |
His belt wont fit your bike without swapping the swingarm and rear shock. I call dibs on the headlights  | ||
| Paint_shaker |
FYI. On my stock motored 04 XB12R race bike, the rev limit is set to 7250. We raced all last season and just today ran Daytona without issue. | ||
| Greg_e |
So how did you do? | ||
| F22raptor |
Piston Speed,piston speed,that is the limiting factor..........  | ||
| Oddball |
Get a cityx, instant rpm increase.  | ||
| Sloppy |
BEFORE YOU INCREASE YOUR RPM YOU MUST FIRST DETERMINE WHAT YOUR PISTON SPEEDS ARE!!! Know this - there are VERY few bikes (and even less cars) whose piston speeds are as high as a Buell's. Remember that BS story of Yamaha's having a 16,000+ rpm redline - those in the "know" knew it was BS because they figured out the engine's piston speed. So once you figure out you piston speeds, you then figure out HOW LONG DO YOU WANT YOUR ENGINE TO LAST? Faster piston speeds = less life of your engine. It's obvious that you know how to do independent research - so figure out what your "proposed" piston speeds are going to be and let us know what they are. BTW, if you're doing this to get a "faster bike", then you shouldn't be working on the hardware. You should be working on the software first... go schedule a track day and you'll quickly realize that a bike with HALF your power can run circles around you... And once you get enough track time, you can do the same to an R1... and that's spoken from experience. | ||
| Vospertw |
Don't want to hijack the OP's post, but for the new guy here - does the XB12 have a rev limiter (other than the one located directly behind the airbox cover...)? I've poked around this site and the service manual with no luck. | ||
| Froggy |
All XB models have several rev limiters, they are programmed in the ECM. The box on your airbox cover is the exhaust actuator. | ||
| Vospertw |
Thanks Froggy. I figured it would but didn't want to run the RPM up one day and find out I was wrong. As far as the airbox cover, I was making an obviously unfunny reference to the rider being one of the rev limiters... Monday morning - cut me some slack. | ||
| Paint_shaker |
Greg, Sixth. It was a helluva battle for last place, which I ultimately lost!! LOL | ||
| Greg_e |
Sixth is not bad on an aircooled machine that most consider underpowered. | ||
| Surveyor |
I have run my XB9r on the track for several seasons bouncing regularly off a +500rpm rev limit without problem............so far. I understand that the 12 engine is more rev limit critical due to it's longer stroke. | ||
| Shockeere |
Thank you all for your comments! I went back and did some research for myself. I don't think that the valve train is the limiting factor, as our 900s share the same valve train equipment and spin freely to 7500. Perhaps the upper end needs some work to get to 8000, but Piston speeds really do get monumental at that level. Slaughter, what did you do to your bottom end to beef it up? was it just the Timken bearings? I am running stock cams currently. In my experience, I choose cams to give me a better top end performance level, which usually requires more rpm. I would like to get bigger cam but I need to do some more research first. Do our cams run out of steam at our current red lines? If the bike really ceases to make power than the risk is definitely worth the reward. What did the 08s get to have a 300 rpm increase? lighter pistons to reduce piston momentum? | ||
| Not_purple_s2 |
08 models have crank with bigger pins and better oiling system developed from the XBRR project | ||
| Chippy |
pm firebolteric_ma and ask him about increasing the rev limiter. he did. Ps. he now rides a honda... Pps. it in't a vtwin either. | ||
| Slaughter |
I had to totally rebuild the motor after a total wadding-up. Put 2008 flywheels and big end bearings in her. Keep in mind, I'm running the XB9 stroke (3 1/8) and bored it out to 3 13/16 - for 1169cc. I spin to 8000 (soft rev limit) - 8200 (hard rev limit) I had John Dahmer at Hoban Brothers/Darkhorse Crank Works to the mods. They did ALL of Paul James racing mods and knew how to build a motor to last. Dahmer is very responsive http://www.darkhorsecrankworks.com/ (Message edited by slaughter on March 08, 2010) | ||
| Slaughter |
Pic of stock flywheel (03) and the 08 - also lightened/balanced - note bigger main bearing.  You might not want to have it lightened but certainly worth having it balanced with lighter pistons! | ||
| Aptbldr |
Do race setups use OEM isolators & links? Enjoying your posts, Slaughter. |
