| Author | Message | ||
     Biknut |
i would like to know if a xb12 r and s have the same gearing? what is the theoretical road speed at 6500 rpm? thanks in advance. | ||
| M1combat |
The ratios are the same, although I hear you take much more of a beating at those speeds on an S model. At 6500 I would estimate 124-127MPH. | ||
| Biknut |
gee i thought it would be more than that. a stock 1200 sportster (5 speed) is 139mph @ 6500. my 4 speed 1200 stock is 120 @ 6500 | ||
| Wyckedflesh |
When mine was configured as strictly an "S" model it would top out at 135mph indicated. With the "R" fairing and laying down on the tank I have crept just past 140mph indicated. The motors have the power for more top speed but the stock gearing isn't set up for more. | ||
| Biknut |
what i've heard is the indicated is not very accurate at high speeds. i would like to know the actual speed at 6500 rpm for comparison. | ||
| Wyckedflesh |
I would rather not get tagged by the radar gun to give you that top speed. Also the numbers your showing for the Sporties seems a tad high. I will admit I could be wrong but the top 4speed stock sporty was something like 95mph and MCnews topped out a 2004 1200sporty at 123mph. | ||
| Firemanjim |
Check out Paul's report of running his XB at Lake Gardiner in Australia.I seem to remember a best of mid 120's as you run into a 2 step rev limiter.Should be in the Tale section.Or just wait for him to see this thread--- | ||
| Biknut |
yea i know a stock sportsters won't do 139. i'm just talking about the theoretical speed you get from the stock gearing. | ||
| Ingemar |
yea i know a stock sportsters won't do 139 You're right! My sportster 1200S did 220 kmh (137mhp) on the speedometer.  | ||
| Rick_a |
Well, ALL production speedo's are a bit optimistic. I laugh when people tell me how much faster their old big twins were (I use a calibrated digital bicycle speedo). Anyway, Harley/Buell speedo's are some of the most accurate (dangerously so by one magazines account)...I guess it's unsafe to know how fast you're actually going? Japanese factories are notorious for having the least accurate. I hear too many, "yeah, the magazines are wrong, mine's gone 175, dude!" | ||
| Court |
>>>Anyway, Harley/Buell speedo's are some of the most accurate May I quote you? Buells have, up until a couple years ago, had quite notoriously inaccurate speedos. The saving grace was that the degree to which they were inaccurate was well known...I seem to recall 4.5% but may be wrong. In this day and age, having GPS units so cheap, a speedo would be the last source I would consult if I needed to know ACCURATE speed. I never have. I used measured miles for testing in the old days and GPS or a calibrated bicycle speedo now. Old timers will recall the stopwatches attached to the panels of many of my old Buells. In addition, if you are going 175MPH it should be on the salt and your time will be handed to you accurate to within .000.  | ||
| Glitch |
Court, 4.5% is as good as it wonderful! Buell does have one of the most accurate speedos on production bikes out there. Japanese bikes can be off as much as 10% and it gets worse the faster you go. | ||
| Bud |
mine did 150 m/h on the dyno that is  | ||
| Biknut |
if this information is not published then finding the answer requires putting the pencil to the paper. i'm too dumb to figure out how to do that. i was hoping a xb owner out there might also be a rocket scientist. this graf is for a 1200 sportster.  | ||
| Glitch |
I think it is written somewhere on what ever it is they write on somewhere an XB12 will do 137mph. | ||
| Biknut |
ok, 137 mph, i assume that's at 6800 rpm. that would make it 130.95 @ 6500rpm. now we're getting somewhere. | ||
| Court |
My GUESS is that it's darn close to 125.243 MPH for a BONE STOCK Buell XB12.  | ||
| Glitch |
Yeah that's what they do in the real world, but, I thought we were talking about what it'll do on paper. Is that PaulinOz? Nice guy, got to meet him at the Ridge Run last month. | ||
| Court |
That is Paul and he is fairly nice but for the damage he and FMJH did to my house! The XB "in theory" speed is greater than Paul's, he was EMC limited. Next year, I hope he can narrow the practical and theoretical gap. Court | ||
| Rick_a |
Some Japanese and Italian brands have speedos that can read up to 15% optimistic at speed...so as Glitch said, 4.5% is pretty good. | ||
| Wyckedflesh |
Biknut the problem is the revlimiter. Your graph is showing the sporty at 6500rpm, the limiter on the XB cuts in at 6200rpm for the soft then hard at 6800rpm. If the Sporty had the same limiters it would hit soft at 5400rpm and hard at 6000rpm which is the published redline. Which would make the Sporty down to about 115mph IF it had the same revlimiter system as the XB. The Sporty gets overrun the XB doesn't. Playing with RB racings page here http://rbracing-rsr.com/gearspeed.html and punching in 7300rpm for the XB specs (500rpm overrun from redline without the limiter per the Sporty specs) and using the measured diameter of my rear wheel at 23.75inches you get a top speed of 153.41mph at 7300 or at where the revlimiter kicks in you get 130.29mph top at 6200rpm | ||
| Bomber |
according to GPS, my Tuber speedometer is within 3% (it's just a bit optomistic) | ||
| Biknut |
wyckedflesh, that looks like good numbers. based on that, it looks like a xb12 would be doing 136.6 @ 6500 rpm. those are numbers that i can believe. a 1200 sportster must have slightly taller overall gearing than a xb12. | ||
| Wyckedflesh |
The gearing isn't very different between the XB and Sporty. like 1-3% difference. What the real question is...how long will it take the Sporty to hit that top speed VS the XB? | ||
| R1DynaSquid |
Sporties running in the 130 range?? Sounds bit far fetched to me. I have had my Dyna right around 115 indicated on the speedo & believe it when I say there is no way in hell I would ever want to go faster than that on a Harley. Besides she was just about pegged out. | ||
| Court |
>>>according to GPS, my Tuber speedometer is within 3% (it's just a bit optomistic) There is a very good reason for that and I'll bet it's consistent from bike to bike. Remind me to ...... | ||
| Bomber |
I don't mind commiting felonies, but I like to know WHEN I commit them -- an accurate speedometer (I would wrritten speedo to save some keystroked, but that would be wrong) is both a feature AND a benefit as for reminding, you, sir, I'll likely forget to . . . . . | ||
| Fullpower |
i have taken my 1998 sportster up to 6800 in top gear. thats with 21:48 final, and a 140 90 16 rear that calculates out to 138mph. that was the easy part, the hard part was getting it shut down, ran off the end of the drag strip into the weeds a bit. got pretty exciting there for a couple seconds. have not been able to get my XB12 up to rev limit in top gear yet, but Motorcycle Consumer News claims they got 135 mph on radar with their example. | ||
| Fullpower |
the REAL question is when is some one going to figure out how to hack the oem ECM and raise the rpm limit.even a single stage 7500 hard limit would be ok with me. could even make it timed allow 6800 indefinitely, and maybe give us 8 seconds of over-rev to 7500. just enough to squeeze 150 mph before we have to shut down for the corner. thats the kind of race ecm i'm talkin about | ||
| Paulinoz |
The hard limit must be related to the stroke, which in turn gives you piston speed. A higher rev limit will do you no good if the piston traveling at Mach 1 keeps going up when the rod has starated it's down stroke. The XB12R would rev through the soft limit aprox 6200 rpm all the way to the hard limit (indicated on Tach at 7000 rpm) hold there for aprox 3 seconds then shut you down to the soft limit. This is in 5th gear. The soft limit of 6200 gave 125 mph. and if the bike will hold the hard limit it would be (125 devided by 6200) x 7000 = 141 mph. Threfore to do 150 mph with stock gearing you need 7440 rpm indicated. So to do a 150 mph pass on a Std XB12R you need to be at that speed for 6 seconds in the Qtr mile plus time in and out of the measured sectiion. Therfore a Hard limit of 7500 would need to be at least for 12 seconds, ( and pray the engine stays together for that time.) Well thats how I see it anway. | ||
| Firemanjim |
Paul,I was running to 7500 with both the 1250cc and the 88" motors for all runs at Bonneville.XB should have no problem with those nice light valve springs. | ||
| Paulinoz |
"XB should have no problem with those nice light valve springs" Sounds good to me me.Must have somthing to do with our convict past we belive anything that comes from a dude who has a uniform. Now if a certain Lion owner / tamer from NYC can score me the loan of ECM module I will be good to go in March 2005 | ||
| Jssport |
My XL1200s using stock gearing 29/61 and stock tires got up to 149.254 mph that about 6500 rpm in 5th gear. I also got 110 mph @7200 in 3rd gear, but that's hard on the crank. JimS LSR 540/506 |
