| Author | Message | ||
     Thruster |
I was coasting down a long gradual downhill on my 08 Uly, in neutral (to rest my left hand), at a steady 25 mph, on smooth dry pavement without pebbles or other debris. As I approached the bottom of the hill, I pulled in the clutch lever all the way, a few seconds later shifted from neutral to first (with the bike still rolling along at 25 mph), and at that instant, I felt a strong kick, while the clutch was still fully disengaged, and the drive belt immediately snapped and fell to the pavement. The bike did not lurch forward or back, nor did it wheelie when this happened. I am the original owner and have always been gentle with it, as it's my main commuting machine. 1. What is the diagnosis? How and why did the belt break? 2. Did I do anything wrong in how I operated the bike? 3. Inspecting the bike afterwards, I noticed the wire clutch cable retainer was broken, the cable housing was touching the front header, and a hole was melted through the rubber boot on the cable housing. Could this have compromised clutch operation enough to cause the belt to break? 4. This occurred six weeks ago. The dealer says the replacement belt is still back-ordered, maybe for another week or two. Has Buell not been producing any bikes for two months, or are they just too lazy to pull a belt from their production supply stream? They were informed right away that the bike is my primary mode of transpo (I ride a bicycle otherwise -- no cars!). I guess selling new bikes takes priority over servicing bikes already sold. 5. Since I first got the bike in Oct 07, whenever I shift from neutral to first, I have felt a slight kick. I've always thought this was normal, perhaps having something to do with the engine flywheel, but now I'm worried that this may have been a milder form of the problem that caused the belt to break. Is there something about the flywheel or something else in the engine, clutch, or transmission, normal or abnormal, that caused the drive belt to snap? 6. Buell customer service was not really helpful regarding my questions. The dealer also would not say what might have happened until they get the new belt and start working on the bike. I'm not too hopeful about getting a correct diagnosis, since both seemed intent on pushing the stupid pebble excuse, which is clearly not what happened here. Any help from readers would be greatly appreciated. | ||
| Skully |
Oleh, How many miles does the bike have on it now? It's possible that something damaged the belt previously and downshifting into first simply supplied enough of a shock load to break it. According to the engineer that I spoke with at Goodyear, the maximum load they measured on the belt was 5,000 lbs and that occurred during shifting. The tensile strength of the belt is 7,500 lbs. The belts have been recently upgraded but I don't recall what the tensile strength is now. Keith | ||
| Swordsman |
But what would make it snap with ZERO pressure on it? He had the clutch in... everything was freewheeling...? ~SM | ||
| Thruster |
The bike has about 9000 miles on it, almost all of it from my 50 mi/day commuting since Oct 07, with no history of accidents or stunting. SM, The belt got strongly "kicked" during the shift from neutral to first, demonstrating a large impulse of sudden pressure, definitely not zero, even with the clutch lever pulled in. That's why I was suggesting that the flywheel may be somehow involved. Maybe the intertia of the flywheel turning slowly (engine was only at idle speed) strongly resisted the faster speed of the transmission when shifted into first gear while coasting at 25 mph. Maybe some kind of synchronizers remain engaged even when the clutch is fully disengaged. I think synchronizers by themselves would not be heavy enough to carry the large amount of inertia required to snap the belt. I don't know anything about the construction of the transmission, so my speculation about synchronizers is purely hypothetical, but it's the best idea I've got so far. Hopefully, someone on BadWeb will be able to tell me what really happened. | ||
| Swordsman |
I was talking about zero pressure on the belt... so long as the clutch was pulled, there shouldn't have been any way for the the engine/tranny to have any impact on the belt. At least not in my experience. I'm also a noob as to how it all fits together, but I know when I have my clutch pulled, nothing else seems to effect the rear wheel, which is mechanically fixed to that belt. My guess is that your clutch WASN'T fully disengaged. ~SM (Message edited by Swordsman on August 25, 2008) | ||
| Hughlysses |
I think there would have been a significant impact load to the belt. The transmission output shaft was spinning at ~25 MPH equivalent, the transmission input shaft was at ~zero. When you engaged first, the input shaft had to instantly come up to a couple of thousand RPM or so, which would have put a pretty big "reverse" impact load on the belt. I sure wouldn't have expected it to break, but maybe you just discovered something we should never do. BTW- there's a thread on how the belt backorder problem was evidently corrected here: http://www.badweatherbikers.com/buell/messages/142 838/387545.html Not sure if they can get your belt any sooner, but you might e-mail Court and ask. | ||
| Ekass13 |
Am I the only one that thinks down shifting into first at 25mph is bad? In fact the only time I ever down shift into first is when I’m going to basically stop. There is enough tq in 2nd even in my 9 to pull out of a near stop. | ||
| Thruster |
The clutch lever WAS fully pulled-in. I very carefully and methodically noted exactly what I was doing because I had felt a similar "kick", albeit milder, once before about a week earlier near the bottom of the same hill, under exactly the same conditions, and noted then that the behavior was unexpected. I believe also that the clutch itself WAS fully disengaged, as the bike has never had a tendency to creep forward the least bit with the clutch lever pulled in all the way, tranny in first, both brakes off, waiting for a light to turn green. On the handful of other occasions that I did coast in neutral on that hill, I either shifted into second (no kick) or if I intended to shift from neutral to first, I blipped the throttle before shifting (also no kick). I only got the kick when the engine was at idle speed when I shifted from neutral to first while coasting. If you're adventurous, give it a try yourself and see what happens! As I said before, all it takes is 25 mph, so the "risk of death" is minimal. | ||
| Thruster |
Thanks Hugh, best explanation so far. I was intending to come to a full stop using just my brakes while keeping the clutch lever pulled in all the way, and already be in first, ready to pull out of the intersection when clear. I did not consider my actions foolhardy, as I had the clutch lever pulled in all the way the whole time. We may indeed have identified something fundamental that we shouldn't do, despite the fact that it did not make it into the owner's manual. | ||
| Swordsman |
"When you engaged first, the input shaft had to instantly come up to a couple of thousand RPM or so, which would have put a pretty big "reverse" impact load on the belt." With the clutch pulled...? How would the force be transmitted? Don't the clutch plates separate the two elements? I'm befuddled....  ~SM (Message edited by Swordsman on August 25, 2008) | ||
| Husky |
I just had a brain fart. Maybe it broke because it had a tension shock load on the part of the belt that goes over the belt tensioner pulley. That would cause a reverse bending load on the belt, which is not the normal load the belt was designed for? This plus the fact under this condition the rear shock is fully extended, which by itself seems to cause a greater load on the belt due to the tensioner pulley. Add them up and you may have exceeded the belts capacity..... Just a thought Husky | ||
| Ekass13 |
Wow this is something because my bike wont allow me to shift into first at that speed; it makes some kinda grinding noise. Other then that its a very smooth tranny, well... for Buells. Oh and Maybe it broke because it had a tension shock load on the part of the belt that goes over the belt tensioner pulley. That would cause a reverse bending load on the belt, which is not the normal load the belt was designed for? This plus the fact under this condition the rear shock is fully extended, which by itself seems to cause a greater load on the belt due to the tensioner pulley. Add them up and you may have exceeded the belts capacity..... Just a thought I think your onto something... | ||
| Thruster |
SM, What Hugh said implies that the input shaft is on the tranny side of the clutch, not on the engine side. The fact that I coasted in neutral for a few blocks implies that the input shaft probably came to rest, since it was not being driven from either the engine side (because the clutch was disengaged) or from the tranny side (because the tranny was in neutral). When I engaged first, the resting inertia of the input shaft brought the tranny to a sudden stop, the resultant force on the belt was too great for it to bear, so the belt just snapped. I initially didn't think that any parts of the tranny would be heavy enough to provide enough inertia to snap the belt, but I now think that Hugh's right -- even the relatively low mass of the input shaft can apparently provide enough resting inertia to cause the belt to snap if there's a large enough velocity differential applied over a short enough period of time. As good as the Buells are, I guess they're still not quite ready for "Impulse Drive"! | ||
| Thruster |
Hugh's explanation also beautifully accounts for why the bike kicks a little when shifting from neutral to first when just getting under way after warming up. While warming up, the clutch lever is out, so the input shaft is spinning, but the tranny is at rest (in neutral). If I pull in the clutch and then shift into first right away, the tranny, which is standing still, will suddenly try to stop the still-spinning input shaft (note that the clutch is already disengaged, but the input shaft is still spinning from its own rotational inertia). The belt then takes a hit in this situation as well, due to the resting inertia of the rear wheel, the traction of the rear tire against the pavement, and the inertia of the resting tranny components, but usually this kick is not so bad. The effect can be ameliorated by waiting a little longer after pulling in the clutch lever and before shifting into first, to give the input shaft time to slow down, just from friction. Conversely, not that I'd ever want to try it, but I suppose the effect can be accentuated by revving the engine while still in neutral with the clutch engaged (lever out), then quickly pulling the clutch lever in and then shifting into first right away. "Reverse Impulse Drive"! | ||
| Chessm |
anyone know what the tensile strength is for the average motorcycle drive chain? | ||
| Husky |
http://www.didchain.com/specs.htm take your pick, you would probably choose 50(530)VM Husky | ||
| Chessm |
^ ah thanks for putting it in context | ||
| Skully |
On my way home this evening, I tried downshifting to first at 25 mph: no problem at all. Then I tried it again at 30, and then at 40. No problems, no gear clash, nothing. Just a smooth downshift. I don't recommend letting the clutch out too quickly at the higher speeds though! Keith | ||
| Jake_blues |
Word of advice on backordered parts: you have to take the initiative to find the part from another dealer(your dealer should be able to pull up who has the part in their computer, or you can use the dealer locater on Buell.com to get the #s to your local dealers), because the dealers won't go through the trouble to call around for you. They can still buy the part and it it still be covered under warranty. I just went through the same thing with my Firebolt(Voltage Regulator though) but pulled my bike out of the shop because the Shop manager is a jerk and I don't want anyone at H-D of Jackson touching my bike. At least they told you yours was on backorder, I had to wait 3 and 1/2 weeks before anyone told me(and they only did so because I reported them to the HD/Buell customer service). | ||
| Iamarchangel |
There's a number of reasons why long coasting is bad for an engine. This would be another one. I would go with the sudden addition of torque to the belt. | ||
| Thruster |
Keith, My scenario is not the same as simply downshifting at whatever speed. Rather, it involves conditions that cause a much wider disparity between input and output shafts before engaging the gears. Coasting in neutral allowed the input drive shaft RPM's to diminish to engine idle speed, and when I pulled in the clutch lever, the RPM's diminished even further. Meanwhile, the output shaft was still going fast due to the coasting. The reverse scenario, which I already described earlier (shifting into first after warming up), involves a stationary output shaft with a rapidly-turning input shaft. I wish they taught us this stuff in riding classes so I wouldn't have to learn the hard way (I took the Rider's Edge class). | ||
| Punkid8888 |
I think it sounds like you either had a poorly manufactured belt, or picked up a rock or something that started a weak point. I really can't see anything that you did that would break the belt. just bad luck get the new belt and try the exact same thing. It will be fie | ||
| Skully |
I still can't imagine the inertia of the gearbox coming anywhere near developing 7500 lbs tension in the belt! I agree with Punkid; there must have been damage to the belt previously. (Message edited by skully on August 26, 2008) | ||
| Ekass13 |
Skully you downshift into first at 40 with no problems? What rpm is that in 1st gear? On my nine 40mph's would be 4000 rpm in 2nd and power in first up top is hard to keep the front down, making as you said "I don't recommend letting the clutch out too quickly at the higher speeds though!" I'll rev out first but downshifting into first at 40 is something. | ||
| Thruster |
Al (AmericanSportBike.com, in case you don't know yet) offered the following bit of enlightenment: -------- 1) The scenario you describe can be as hard or harder on the belt than what can be done with "normal" operation. You generally only shift into neutral when you're coasting to a stop. If you DO put it in neutral and then go to re-engage the driveline, you really need to rev the engine and match the engine speed somewhat closely to what it would be at the gear and speed you're at PRIOR to releasing the clutch, and you always want to select a higher gear for that speed, not a lower gear. Otherwise you subject the driveline to MUCH higher forces than you can ever provide by the engine alone. I very rarely shift into neutral while moving unless I'm about to stop, and if I do, I will upshift it prior to slipping the clutch in, and always with a blip of the throttle prior to engaging the clutch. 2)See 1) 3)Not a chance. Buell has released a new clamp for the clutch cable, that wireform has been a perpetual failure point. But it had nothing to do with your belt failure. 4) I hear ya. Spare parts fulfillment is a totally different profit center, run more by Harley than the Buell factory. The Buell production line is a JIT operation, and orders to keep that line going are managed completely different than the spare parts fulfillment processes. Different folks, different systems. 5) That is fairly normal, how much is does that is related to how well the clutch is adjusted. If the clutch isn't fully disengaged, there will be a larger clunk. Also, when the engine is cold, the oil is much thicker and there is much more clutch drag, so there is generally a bit larger a clunk into gear on a cold engine than on a hot engine. I doubt that it had any bearing on your belt failure. 6) Pebble, maybe. When was the rear wheel removed last for tire service? Who did it? While the 04 belt is less twist sensitive than the 03 belt, and the 06 belt is less sensitive than the 04 belt, it can still be damaged if someone doesn't minimize the amount of twist that is input into the belt. That is as likely, or more so, the major contributor to the failure. Al -------- I missed that the clutch was fully disengaged through the whole thing, should have read more closely. That will certainly lessen the loads, but the loads don't go to zero. Enough to break a belt? Doesn't seem likely. But I've heard that clunk before, and it isn't a good one. It's why I don't coast in neutral. With the bike coasting in neutral, the final drive gear, and it's mating gear on the counter shaft, and the countershaft itself, are spinning at the same speeds that they would be if you were engaged normally, driven by the rear wheel. The mainshaft, OTOH, is spinning at the normal speed of the clutch basket connected to the idling engine if the clutch was not pulled in while it was coasting in neutral. Even with the clutch pulled in, with any time coasting, your clutch behaves much like an automatic transmission in that there is viscoelastic fluid coupling between the driving and driven plates in your clutch, so the mainshaft will approach the speed of the clutch basket because there is little to no load on it, only inertial acceleration loads. At the moment that you put it in gear, you now instantaneously are trying to make the mainshaft and countershaft match speeds (per the driving/driven gear ratios). With the clutch disengaged, you aren't trying to instantaneously make the ENGINE match that speed. But the mainshaft has a few big heavy gears on it , as well as the internal clutch hub (not the basket) that are ALWAYS spinning at mainshaft speed, so there is a lot of inertia in that shaft. The countershaft that has gears that are coupled and uncoupled from the countershaft speed, it doesn't have anywhere near the inertia of the mainshaft. Note that clutch engaged or disengaged ONLY affects the engine (clutch basket, primary chain, rotor, flywheel, pistons, etc) speed relative to these events, so clutch slip does NOT lessen the load due to the mainshaft inertial effects, only the engine inertial effects. I wouldn't expect that those loads are enough to break a perfectly good belt. But it's an ugly clunk that occurs, and a pretty instantaneous one. There is NO clutch slip on that engagement as there is on an engine downshift. It is an instantaneous spin up. If you're ever coasting in neutral and then want to put it into ANY gear, your best bet is to leave the clutch engaged, blip the engine RPMs high to accelerate the mainshaft, then clutch in and shift into gear so that the mainshaft is already spinning at or above the RPMs it will need to be at after engaging the countershaft. I suspect your belt was already damaged in some way and that the mainshaft inertial loads were just the proverbial straw. Al | ||
| Blake |
By virtue of its wet clutch configuration, there is always some transfer of torque between the input and output sides of the clutch, more so if the transmission is not yet hot or is overfilled. It's always a good idea to blip the throttle when shifting from neutral into 1st gear. This helps get the input and output of the clutch spinning at closer to the same rate and it also helps fling excess oil off the clutch plates, thus reducing the viscous transfer of torque even with clutch fully disengaged. | ||
| Prowler |
This being the case(?): "At the moment that you put it in gear, you now instantaneously are trying to make the mainshaft and countershaft match speeds (per the driving/driven gear ratios). With the clutch disengaged, you aren't trying to instantaneously make the ENGINE match that speed. But the mainshaft has a few big heavy gears on it , as well as the internal clutch hub (not the basket) that are ALWAYS spinning at mainshaft speed, so there is a lot of inertia in that shaft. The countershaft that has gears that are coupled and uncoupled from the countershaft speed, it doesn't have anywhere near the inertia of the mainshaft. Note that clutch engaged or disengaged ONLY affects the engine (clutch basket, primary chain, rotor, flywheel, pistons, etc) speed relative to these events, so clutch slip does NOT lessen the load due to the mainshaft inertial effects, only the engine inertial effects." Plus the fact that when the Uly rear end is unloaded (when braking or downshifting), the belt is stretched to it's highest loaded position (which has been noted to be 25% higher than any other Buell model). Combination of the two along with a flaw in your belt (crack in the rubber/composite casing or defect/puncture in the belt) possibly could have caused your belt failure. (Message edited by prowler on August 26, 2008) | ||
| Thruster |
Blake, I believe your recommendation to blip the throttle applies when moving, not when standing still. Thus, when coasting in neutral and intending to shift into first, the following sequence will avoid the strain on the belt: 1. Blip the throttle while the clutch is still engaged (this spins up the mainshaft of the tranny to match the countershaft more closely); 2. Pull in the clutch lever (the mainshaft will keep spinning from its own inertia); 3. Before the spinning of the mainshaft diminishes (from friction), shift from neutral into first. If you pull in the clutch lever before you blip, the blip will not spin up the mainshaft as needed to match the countershaft. This maneuver seems like a nuisance. I'd rather not bother and instead just brake to a full stop while still in neutral. If I'm standing still in neutral (whether about to get underway after initial warm-up or just stopped at an intersection), the countershaft is at rest, not spinning, so the situation is opposite: 1. Pull in the clutch lever; 2. Wait for the mainshaft to come to rest (from friction, guessing 5 to 10 sec may be enough to go from idle speed to zero); 3. Shift from neutral into first (clunk should then be minimal to none). A quick blip before pulling in the lever may indeed fling some excess oil off the plates, but I don't think it would help, and may be counterproductive, as you then may have to wait a little longer for the mainshaft to come to rest before shifting from neutral into first. Note: I'm using Al's terminology here: mainshaft = input shaft to the tranny; countershaft = output shaft of the tranny. Prowler, Are you implying the designers might have made a calculation error in positioning the belt idler pulley on the Uly? It's supposed to be carefully positioned to maintain a constant belt path length throughout the range of swingarm movement. I'm guessing maybe they were lazy and failed to redo the calculations when they increased the swingarm travel in the Uly design. Do you think Uly owners ought to get an aftermarket spring-loaded idler to compensate, or would the added slop open up a whole new category of issues and risks? It may also be an issue that the geometric constraints are such that a fixed idler can accommodate only a narrow range of swingarm motion, even if perfectly positioned, so the greater range of swingarm motion on the Uly may necessitate a moving idler via a more complex set of linkages, something the designers might not have been willing to undertake. Whatever; just speculating. How dead do you guys think we can beat this horse? I'm still having fun, but I do think we're almost done... | ||
| Pkforbes87 |
The belt on my X1 broke as I was slowing to a stop as well, but I never felt anything. I waited at the intersection completely oblivious, and when the light turned green and the bike wouldn't move, there was the belt laying about 10 feet behind me. Now that I think about it, the majority of riders I've talked to who use a belt drive setup experienced a break while slowing and/or shifting. | ||
| Thruster |
Much thanks for that, Phil! I've been waiting for a comment like that. It's an issue that I think is very important to understand, but I've not seen it addressed at all in Motorcycle School, books, magazines, forums, or blogs. Maybe most people don't have the time or patience to work through the gnarly concepts, but I at least would have liked to see a paragraph explaining this in the owner's manual. I wonder what percentage of broken (and backordered) belts have been due to this issue! Once this thread quiets down, maybe I'll send a copy to Buell. |
