| Author | Message | ||
     Mxer83 |
what is the best way to change an xb9r to a xb12r, or what is the best bore job size ? keep in mind this is a track only bike, all input appreciated ! | ||
| Fmaxwell |
Honestly: Sell it and buy an XB12R. I'm not trying to be a wet blanket, but the difference in resale between the two is way less than the cost of converting an XB9 to an XB12. Just off the top of my head, I can come up with a whole host of things that would need to change: Crankshaft, rods, pistons (pretty sure that they are different), primary drive chain and sprockets, exhaust headers and muffler, throttle body and intake manifold, ECM, heads (bigger ports), and clutch spring. You have a bunch of expensive parts to replace and a lot of labor to do it. And that's assuming that nothing goes wrong. | ||
| Diablobrian |
I think that Mxer83 is talking about a big bore shorter stroke motor rather than converting it into an actual XB12. The short stroke motor is preferred by a lot of teams at the track over the longer stroke motor. For a street bike however you may be better off trading your 9 in on a 12. Unless you have specific reasons for wanting the short stroke motor. | ||
| Brent_crossbronkos |
"For a street bike however you may be better off trading your 9 in on a 12.." - I agree but a big bore short stroke XB would be pretty cool! | ||
| Bads1 |
Mxer83 said, keep in mind this is a track only bike, all input appreciated ! | ||
| Saintly |
heads (bigger ports), Nope. Heads are identical. | ||
| Fmaxwell |
Saintly wrote: Nope. Heads are identical. Wow, I'd thought that the heads were different given that Buell upped the size of both the exhaust headers and the throttle body. My bad -- should have checked part numbers. Thanks for straightening out that bit of misinformation I posted. | ||
| Fmaxwell |
Brent_crossbronkos wrote: I agree but a big bore short stroke XB would be pretty cool! I'd be interested in what kind of redline you could reliably support with that combination. You would be keeping piston speed down by having short stroke, but you'd still be slinging bigger, probably heavier pistons at the ends of the rods. | ||
| Diablobrian |
For track only the displacement limits of the classes you run will dictate what bore you should run. Octane rating of available fuel will dictate what compression ratio you should be looking at too. No sense in building a motor that you can't legally run, or one that you have to have fuel shipped in for. Motors should be built as systems for a specific goal. If you have too narrow of a perspective on it you won't get the maximum bang for your buck. The parts need to work cooperatively. | ||
| Hogs |
The Thunder class buells that just raced here along with Ducs. and bmw`s they all have to meet Horsepower class I think its 1 HP per 3.8 lbs.. So around a 100 RWHP give or take is all that is allowed | ||
| Rick_a |
For sure a big bore on a 9 crank would be the way to go. 3-13/16" is pretty common. It'd be an 1170cc screamer. | ||
| Slaughter |
3 13/16 with the stock 3 1/8 stroke gets you a motor that makes almost identical power to the 12 but it'll spin up faster. Lighten and balance the crank/rod/pistons and it'll rev REALLY quick. Unfortunately, it is a pricey mod but for racing, it's a great way to go. | ||
| Djkaplan |
I'd be interested in what kind of redline you could reliably support with that combination. If the stroke stays the same, so does piston speed. The absolute redline would be the same no matter what the bore. | ||
| Fmaxwell |
If the stroke stays the same, so does piston speed. True. The absolute redline would be the same no matter what the bore. Untrue. The redline is related to piston speed, piston mass, connecting rod mass, and the ability of the crank and connecting rod bearings to withstand the loads. (In our case, the valvetrain is not an issue.) If piston mass increases, then the redline limit decreases. Decrease the mass of the piston and the redline limit increases. Just look at the 2008 Buell XB12 engines: They have a 300rpm higher redline and the way that they accomplished it was with lighter pistons, stronger connecting rods, and larger diameter bearings. There was no change to bore or stroke. This all relates to the maximum positive and negative piston acceleration. Maximum positive occurs near top dead center. This is when the rod is being stretched as the piston is pulled down the cylinder bore away from top dead center. Maximum negative piston acceleration near bottom dead center. Here, the rod is being compressed as the piston is pushed back up the cylinder bore from bottom dead center. The more massive the piston, the greater the positive and negative loads imposed on the rod, rod bearings, and (in an unbalanced engine like ours) the crankshaft bearings. Piston speed is a part of the equation, but increased piston mass is what may change the redline in this situation. | ||
| Slaughter |
Many of the 3 13/16 pistons are actually same weight or even lighter than the stockers. Hence the higher redline POTENTIAL. I'd tend to stick with the stock redline UNLESS you're just planning on more rebuilds - there's a whole lot of slamming and banging going on, not just small end and big end bearings. (Message edited by slaughter on August 20, 2007) | ||
| Xb9 |
You need a couple of these 3 7/8 inchers with 15 degree squish CP racng pistons, 12:1:   Then you got to do some headwork to feed 'em   Along with a whole bunch of other goodies to make it all work. You'll spend some money, but a short stroke 1208cc torque monster that revs all day to 7500 is a whole lotta fun to ride! Call Brian Nallin at Revolution Performance and he can set you up. | ||
| Hogs |
XB9... Cut that OUT you are making me Drool... I got the ITCH to do the 1450 but have been asking ?`s all the UK forums/and here and there and sponsors and all say don`t go there.. use the xb9 but I want the 1450 not 1250 oh well... I can dream..>! someday...! I still think the NEw Xb`s will have a 1350 or so kit coming soon for the nEW 12`s | ||
| Slaughter |
XB9 - you can get those into the cases and still get enough metal left for the studs? Know how big the spigot bore is? Wondering if he's got a slightly bigger bore in the cylinders (thinner wall)?? 1/16 more bore diameter - interesting... but for racing, it'd bump me over 1200cc which limits the number of classes available but for a streetbike??? SWEET!!! I just know how little aluminum I have left after boring the cases for 3 13/16 and there's just not much "meat" left for a bigger bore. | ||
| Xb9 |
oh yea the Darkhorse crank:  | ||
| Xb9 |
You can see in the last pic where the cases are bored to fit the spigots - you can't go any further. I think Brian does use a thinner wall spigot with the Nikasil bore. You'd have to ask him. I just had this down for inspection after about 1500 track miles and 1000 street miles and everthing looks perfect, like new. I run 110 Octane race gas at the track, but with a little mapping it runs fine on the street with 93 Octane. Had to go to an XBRR oil cooler to keep the temps down, it creates some BTU's. (Message edited by xb9 on August 20, 2007) | ||
| Hogs |
BY any chance wd. ya have a picture without the jugs on to see the bored out holes? OH ok I see now... also see the pin is welded interesting.... (Message edited by hogs on August 20, 2007) (Message edited by hogs on August 20, 2007) | ||
| Slaughter |
Wow - that's all I can say. Getting my wish list together for the racebike rebuild in the next couple months. | ||
| Hogs |
Xb9, HAve you had the Puppy dyno at all?  | ||
| Xb9 |
nope, not yet. It doesn't get pulled much down the straights by most newer 600's though so it should be right around 110 RWHP. Maybe a little more, just a guess. It will pull them coming off the corners though (585V2 cams). | ||
| Hogs |
NIce.... I may Pm ya later on, on a few ?`s if ya don`t mind... | ||
| 1324 |
Awesome thread, if for nothing more than the pics. By the way, how fast does that thing spin up? | ||
| Xb9 |
Hogs, be glad to answer any questions. It's been a lot of fun to build and ride. 1324, It spins up way faster than a stock motor, it really doesn't sound anything like a stocker either. I'm running the micron, and some people say it sounds kinda like a built small block chevy. It's just got a real bad ass sound, real nasty. When you rev it on the stand, the rear squats from the torque and the quick spin up. I'll have it at the VIR and Mid-Ohio Inside Pass trackdays. (Message edited by xb9 on August 20, 2007) | ||
| Djkaplan |
"The absolute redline would be the same no matter what the bore." "Untrue. The redline is related to piston speed, piston mass, connecting rod mass, and the ability of the crank and connecting rod bearings to withstand the loads. (In our case, the valvetrain is not an issue.)" Thank you for your thoughtful response. I still think rpm capability would be the same, but longevity at that rpm would be less. I agree it's the big end rod bearing that will suffer the most with increased piston weight. Am I correct? Hell if I know. Actually, no matter what weight piston or stroke you used, if you didn't change the ignition, absolute rpm would never change because of the rev-limiter. | ||
| Djkaplan |
"Just look at the 2008 Buell XB12 engines: They have a 300rpm higher redline..." I did not know this. Now I gotta have the 2008 crank and rods! |
