| Author | Message | ||
     Riclyd |
What will the top speed on my XB12S with XB9 primary chain conversion be? | ||
| Gentleman_jon |
You will theoretically lose 11% in top speed. However, whilst a small rider on an XB12 R might achieve the theoretical top speed, I do not believe that a large rider on a Lightning will. Therefor you may not lose that much top speed if any. The Buell like many production motorcycles are over geared not for optimum performance, but also to meet gov't regulations. I have geared my chain driven XB 12 S down about 10% , and I am very happy with the results. I weigh 235# in full gear. Here is an rather boring discussion of the entire matter which I have previously posted. Please don't feel any compulsion to read it. I made these notes in the process of figuring out how to select a rear sprocket for my bike, Lil' Blackie.  Lil’ Blackie Gear Analysis XB12S Stock gearing Primary: 57/37 = 1.5 Secondary: 2.407 = 65/27 total 1.5*2.4= 3.6 gear box ratio in fifth is 1:1 Lil Blackie Final selection primary  ratios from XB nine) 1.676 ( 57/ 34) Secondary chain 46/20 = 2.3 total 1.676*2.3 = 3.85 Rear tire cicumference Dunlop Qualifier 1991 mm =.00123715 miles = (6.53215 feet x 60 min) = .074226 =k Question: How many teeth are required on the rear secondary sprocket so that the final gearing equals the stock XB12S or some other selected ratio. There fore : in the stock set up, each 1000 rpm in fifth equals 1000 engine rmp/1.5 =666.7 rpm /2.4 = 277.8 rpm To get 277 final rpm from 1.67 primary you need a secondary of 2.15 : 1000/1.67 = 599rpm/ 2.15 = 278.5 Leaving the primary unchanged, and using one of the existing rear sprockest we could get the 2.15 final ration with a 50/ 23 combo using the existing 50 tooth rear sprocket or a 43/ 20 using the existing 20 front sprocket. However, we are going to reduce top speed by ten miles an hour, and increase acceleration, using a 46 tooth rear and 20 front sprocket because: a) the rider is larger than average, b) S model is less streamlined than R c) rider prefers acceleration to top speed d) the 20 tooth front sprocket is already installed and Hals said that is the size they normally furnish. Estimate top speed with the selected 46/20 combo total reduction = 1.67*2.3 = 3.841 6800 rpm /1.67 = 4072 rpm/2.30 = 1750 rpm x .00123715 mi. x 60 minutes = 130 mph 4000 rpm/1.67 = 2395 rpm/2.3 =1041 rpmx .00123715 mi. x 60 minutes = 77 mph 3500 rpm/1.67 = 2095rpm/2.3 = 911 rpm x k = 67 mph Estimate stock 6800 rpm/ 1.5 = 4533 rpm /2.407 = 1885 rpm x .00123715 mi. x 60minutes = 139 mph This is mostly like overgearing for 235# rider on S model. . Stock Nine for comparison 7500 rpm/1.67 = 4491 rpm/2.5 = 1796rpm x .00123715 mi. x 60 minutes = 133 mph Lil’ Blackie as Delivered ( It had "Nine" primary with a 57/20 secondary!) 6800rpm/1.67 =4072/.2.85 = 1428 rpm x .00123715 mi. x 60 min. = 106 mph. I think it was set up as a supermotard. (Quick Calculation: Speed = rpm/total reduction *k ex: 6800/3.85*.074226 =131mph) 1000/3.85x.074226=19.2 mph = minimum speed Observed speed: 3000 rpm = 55 mph. Actual calculated = 57.5 so speed is 5% slow. rpm x .0192 = speed ex. 6800 x .0192 = 130.56 | ||
| Stevedplumber |
UH!!?  | ||
| Ustorque |
i believe what jon was trying to say is " when this baby hits 88MPH you're gonna see some serious sh*t"  | ||
| Cereal |
Best movie ever. | ||
| 12r |
i believe what jon was trying to say is " when this baby hits 88MPH you're gonna see some serious sh*t" Great reply  How can anyone ask a question like this when we can't decide if our Buells are Harleys ?  | ||
| Njsxb9 |
Mine is all stock and I hit just below 140mph this weekend on my XB9city | ||
| Diablobrian |
indicated speeds and actual speeds can be far different things. | ||
| Gentleman_jon |
Nick, Nice to see another Long Islander on the board. As Brian has correctly observed, indicated and actual speeds can be far different things. Perhaps you noted in my chain analysis, that the theoretical top speed of the XB9 is 133 mph: Stock Nine for comparison 7500 rpm/1.67 = 4491 rpm/2.5 = 1796rpm x .00123715 mi. x 60 minutes = 133 mph Thus it is rather unlikely that you actually "hit just below 140" although your speedo may have read that high: they are notoriously inaccurate at their upper limits. I might add that I find the speedo rather hard to read accurately at anything over a hundred on a Lightning. What with the drag of a Lightning, and the hard limit on the rev limiter, actual speeds of over 130 on a Lightning are rare, (and not really advisable on the LIE.) | ||
| Spike |
My brother in law created this gearing calculator a while back: http://www.cryohold.com/bike/gears.html It has an '04 XB12R loaded as a preset. If you load the XB12R, change any of the inputs, then tab to the next field it will regenerate the table below. According to it, the top speed of an XB12 (gear limited) will drop from 137mph to 119mph by switching to the XB9 primary. | ||
| Riclyd |
What must be changed on my XB12 in order to get an XB9 primary gearing and how much will it cost? | ||
| Gentleman_jon |
The XB9 primary gearing kit is available from at least one of our sponsors, American Sport Bike. Cost: $193.10  The kit includes a new primary chain, a new, smaller engine sprocket and a primary chain case gasket. Another alternative, converting to chain secondary drive, does not cost a lot more, using the Saintly chain conversion. This provides the ability to select a wide variety of gear ratios, and eliminates the belt, which has a mixed record of reliability. | ||
| Rigman |
I have an 04 XB12s with XB9 primary gearing. It hits the rev limiter at 127-128 on the speedo. Don't know how accurate the speedo is though but maybe this will help. I'm 175lbs It limits you on a hard take off in 1st because the bike wants to stand up all the time. You can wheelie all day long in 2nd. But cruising at 60mph with a Jardine pipe is loud. I would not recommend it if you do extended amounts of driving over 55mph. | ||
| Hammer71 |
10 miles per hour | ||
| Fullpower |
So you say your XB9 went 140 Miles Per Hour? I hope you deployed the parachute before impact. |
