swapping primary gears xb12 to xb9

[holleywood]

I am looking for a little more low end grunt from my xb12r. I understand swapping the engine sprocket in the primary from the xb12 to one of an xb9 can make a considerable difference. This will be a change from 38 teeth to 34. Has anyone here done this? And, what did you discover?

 

[TCazes]

Free bump for curiosity sake

 

[oh9bolt]

Click Me

 

[50dro]

As 09 showed...lots of threads on this. I just did it on mine and LOVE IT!!! You'll lose some top end but it's a blast everywhere else!

 

[LocoLobo]

Is it just the sprocket that's replaced, or do you have to replace the chain also?

 

[50dro]

both

 

[holleywood]

Yes, I found Artur's thread, after some digging, about the swap. I hopped on the Buell wagon late. There is a wealth of info out there but sometimes its difficult to find. I don't mind losing a little top end for a bit more grunt. My biggest concerns were how much top end I would lose for a gain in acceleration and front wheel lift. Punching the numbers my bike runs 80 mph at about 4k. This gives me a theoretical top speed of about 136 mph at 6800 rpm. Swapping to an XB9 sprocket and chain seems like approximately 11% change in gearing. Which should net about 4500 rpm at 80 mph. Top speed at 6800 rpm should be about 120 mph.
I am just trying to verify my numbers are on the right track. I would like to hear from others who have done the swap. Thanks 50dro!
I like to wheelie and ride the mountains. Riding the 421 "the Snake" this weekend with a friend who owns an 1100 Monster I determined my xb12r is too civil. I want a lot more aggressive asphalt chewing torque monster. So, those who have changed engine sprockets, was this a change you were happy with or would you just prefer to undo the modification?
Thanks

 

[TCazes]

Damn. Guess I won't be doing this one. Sounds rough 4500 at 80 is a no go that shifts the power band way down. I like my 134 top end

 

[lawdog]

I did it and loved it! If you cruise in the city you will enjoy it. Really pulls that front wheel up! LOL If you are a highway cruiser or going on long trips the higher rpms will be a drag. All depends on the riding you do. I don't ride fast so top end is of no concern to me. But I sure do get there quicker! LOL I hate riding on the expressway so I enjoy the swap but if you cruise the expressway I would think twice about it.

 

[50dro]

Top speed at 6800 rpm should be about 120 mph.

Confirmed! I think you'll like it a lot for the type of riding you say you enjoy.

 

[Danicles]

I just bought a 2009 Ulyesses and it has this mod. Great for this bike! I also have a 2009 fire bolt witch it would be a good mod for but I like my top end on that bike. I'm looking into a 90ci kit for the fire bolt and possibly get the heads ported. It would be crazy with the lower primary gearing. It's a sacrifice and gain, just have to decide what you want.

 

[konarider94]

Yes I have done this mod as well. Its a very noticeable change and makes the bike feel a lot more powerful. If you press the sprocket out of the rotor be sure to buy new hardware for installing the new sprocket on the rotor. They come from the dealer with loctite already applied to the bolts.

 

[Jcastro4089]

This may be a dumb question, but I've always wondered. Has anyone ever gone the other direction and put an 12 primary in a 9? I've assumed this would lower the RPMs on the expressway when going 80 but would obviously hurt any low grunt that the 9 has. Again, I've always wondered so I thought I'd take this opportunity to throw it out there.

 

[holleywood]

[up]
Holy Smokes! I ordered a drive gear chain and stator rotor this weekend. These were used off an xb9... I thought I'd give this a go and see if the improvement was worth the effort. Having the rotor already attached made for a quick swap without worrying about damaging the rotor pressing the gear in and out.
As for performance... This is the heat! The front end is weightless now. All other mods (exhaust, race maps, open airbox) are a joke compaired to this. This project cost under 100.00. The bike is nasty now. It tears through the gears as fast as I can shift. Loads of eyeball flattening accellertion. Fifth gear is wide awake now. Less vibration and a whole lot more grunt. Awesome! As for top end... Not sure the engine cold've worked all the way to redline anyway. This mod will get it to redline quickly.
Thanks for the info.
Dave

 

[50dro]

[up]

 

[Bullettooth023]

definitely worth it! makes the bike a wheelie machine

 

[tomahawk1976]

Any suggestions as to where to pick up the xb 9 parts? Looks like a great mod

 

[Bullettooth023]

Just keep an eye out or you can pony up and buy from ASB

 

[Global Eyes]

Just missed this one.

Ebay

 

[UMDterp13]

Yes 12 primary on the 9 puts it around 150 mph (extra 500-700rpm equates to about 12mph as each 1000rpm= 20mph on stock belt xb12 primary) ((1:1 ratio)) but there's a catch. you need 90ish + hp to get there which means at minimum head work & custom tune.

Remember switching ratios on a chain drive bike can also move the speeds around