| Author | Message | ||
     Hootis29 |
I am installing a bigger front drive sprocket, hopefully lower RPMs, and better mileage. Anybody else tried it yet? | ||
| Rotorhead |
How's that work with the belt tension or are you talking about the XB9 primary drive gears? | ||
| Hootis29 |
Not sure yet, I'll probably use the 136t Sporty belt, or adjust the tensioner via some precise machining. We'll see how it goes, it should lower my highway RPM by about 400. | ||
| Hughlysses |
Hootis, I think the Sportster belt is the same length as the Uly belt (Uly belt same length/teeth number as tuber belt = Sportster belt). At any rate, the Sportster belt is not made for the reverse bend the Buell belt gets so it may not hold up. The few people here that have changed the gearing on their Uly's have gone the other way by installing XB9 primary sprockets. | ||
| Hootis29 |
There is a Sporty belt that is a tooth longer. Does'nt the XB 9 gearing giver you a shorter gear? higher RPMs? | ||
| Teeps |
Hootis29 Does'nt the XB 9 gearing giver you a shorter gear? higher RPMs? Yes. | ||
| Rotorhead |
I'm interested in the mod to lower rpm due to the long distance rides I do. 400 RPM would make a huge difference at say 75 MPH. I think it would be like adding a 6th gear I am always looking for. When some posts that has done the mod PN's would be great. I was thinking backwards with my 1st post at the top. My other dream is to have a lower 1st gear. I guess with the ULY you can't have your cake and eat it too. A 9 primary with the 29T mod would cancel each other out or would it? Way to much math for me to figure that out right now. | ||
| Johnboy777 |
I never even use 5th gear on the freeways, but then I don't go above 70-75mph...4th gives me great response in traffic. I doubt whether you'll improve fuel mileage much, if at all, dropping 400RPM - plenty of posts about this. . | ||
| Bad_karma |
Paul Not sure about the XB bikes the 29 tooth on my S3 and I had to be doing above 80 or the motor wouldn't hold the speed. My drop was more like 1200 rpm. I'm interested to see the difference in the two series. Joe | ||
| Hootis29 |
I have no concern about the power. I might look at one of those spung belt tensioners though. I'll keep everyone posted. | ||
| Jlnance |
Hootis29 - Before you do this, I'd try an experiment. Ride to someplace down the interstate about 100 miles away. Go in 5th gear and come back in 4th gear. Check your mileage each way. I did that and discovered I get better mileage on the highway in 4th. If that's the case for you, you obviously don't want to make the change you're describing. Some people get better in 4th and some in 5th. We are really sure why, perhaps it's rider weight or size. But it's worth checking. | ||
| Skyclad |
There is a theory that the improved fuel mileage is due to the engine working closer to it's peak torque speed with the lower gearing. Could also be due to not needing as much throttle to get the same acceleration (and we all know that Uly riders are responsible and wouldn't use the gearing the do more wheelies or anything like that). | ||
| Jammin_joules |
I am surprised someone wants a taller final gear ratio on a Uly. I guess if its use is solely on the highway. Off road, I want the XB9R primary, takes about 5% higher rpm for a given speed. A stock Uly is too fast for some situations IMHO, standing on pegs, clutching to slow down and decide a route, then having nearly a stalled motor, not good on a mountain side. Lowe RPM is obviously better for long term wear & tear. But don't look to better gas mileage. On the highway it is primarily determined by rolling resistance and coefficient of drag, eg. wind resistance. Your frontal area determines that - taller wind screen, size of rider, saddle bags, head wind versus tail wind. But it is not linear so riding into the wind in 5th and with the wind in 4th will yield considerably different results. Most optimum speed is determined by final (total gear ratio) and peak power. Riding near peak at what ever speed that results in will give you most efficient mileage. Hint: it's not at 3,500rpm. | ||
| California |
seems to me . . . what we're saying is that we'd like a six speed, with a lower first and second gear, but with sixth just a tad higher than fifth is now. Wonder how long before the MoCo develops it? | ||
| M_singer |
The idea that a motor is most fuel efficient for steady speed cruising at its peak torque rpm is simply false. If that were the case cars would not have OD gears. I am aware that it is not unusual for a motorcycle to get better fuel economy in 4th gear then in 5th but there are lots of factors at play. | ||
| Jlnance |
what we're saying is that we'd like a six speed, with a lower first and second gear, but with sixth just a tad higher than fifth is now. Wonder how long before the MoCo develops it? I don't even think you would need 6 gears, just spread the current gears out more. I've heard a 6 speed won't pass EPA noise regs. I'm guessing that's also why first is geared so high, and why the shift points in the manual are at such low RPM. | ||
| Rotorhead |
What I'm thinking is with a hardware gear set up and a ECMSPY remap it can all work out in the long run. It would take some dyno time to do it right and allot of that math stuff. | ||
| Arcticktm |
I switched my Uly to the XB9 primary setup (lower gearing) a month ago, and so far I LOVE it! 'Course, my issue was not being able to run smoothly at low speeds (<30mph), and I fried my stock clutch on some slow fireroads last fall. I just went to MB5 (about 160 miles each way) and had no problem with the higher RPM, however I avoid expressways generally on 2 wheels. The bike is way snappier through the gears, and I actually had to be careful on starts on slick wet pavement! Have not measured fuel economy since the change, but several folks on this board have reported higher highway mileage in 4th gear than in 5th stock. Don;t know why a 6 speed would make passing EPA sound any harder. It is a SAE test with a drive by sound measurement at a certain speed (unless it is different than the test I know). No requirement to run any specific gear. KTM used to get their mid 90's dual sports to pass sound by giving them crazy high gearing (top speed was in 4th!), and figuring the customer could change sprockets easily without having to go crazy with the muffler and airbox and other noise suppression. Not sure about bikes, but shift points in car manuals are usually low to provide best EPA fuel economy numbers. | ||
| Jammin_joules |
6th gear I didn't need yesterday, a slower 1st mighta been handy, but even then, it was greasy as the sun melted the frozen road surface  at 8,000 feet it got interesting  But Joules prevailed, a little dirty for the effort. Pingree Point, Roosevelt National Forest.  Next up - Moab, UT 5-7April. | ||
| Hughlysses |
Articktm, One thing I've always wondered about the XB9 primary change, how did your bike work out in the twisties in North Georgia? Did you find yourself having to shift more often, or did the gearing still work out OK? | ||
| Jlnance |
I just went to MB5 (about 160 miles each way) and had no problem with the higher RPM, however I avoid expressways generally on 2 wheels. I don't know either, but supposedly that was Erik Buell's explanation when asked about a 6 speed at Homecoming. Of course it's 3rd hand information by the time it gets to me, so I could be missing some details. I do think there are legal issues at play in all of this, though I don't know what they are. I was told the 1125r has shift points in the manual that have you in 6th gear by 55 mph. That's just insane. I'd love to know what motivated them to do that. | ||
| Arcticktm |
Hughlysses, Bike is working great with the XB9 gearing so far. I did not notice having to shift any more, but it was pretty damp all weekend, so I was not exactly charging hard. I also had brand new tires on, and new front brake pads. I do notice a lot more snap down low. I also changed to the '07 airbox at the same time, but I doubt that accounts for too much of this. Since I live in the twisties (West NC), I am confident this lower gearing is going to be a good thing. Seems like 70mph (indicated) is now about 3600 rpm or so. I did run it up to 100mph indicated, but do not recall the rpm. It's just math at that point, since both were in 5th gear. Jlnance - even my 1980 Suzuki GS650 had crazy low rpm shift point like you mention, so it appears to be an industry wide practice, whatever the root cause. |
