XS11 Transmission - Pictures and Explanation

[xs11]

XS11 Transmission
Pictures and Explanation
by Steve Borenstein

I've had this transmission apart twice now, it's taken a while for me to get a full understanding of what's going on here for each gear. I took a picture of every gear so I could see exactly what's happening in every gear and neutral. I also discovered why neutral-1st shifts are so hard on the transmission. Here's my explanation of things: First off, the microfiche exploded diagram is really helpful in seeing some of the details. Short summary: There are two sets of shafts with gears that are all in constant contact with their countershaft companion. The shaft seen in these pictures is the "Countershaft" or "Drive Axle Shaft". This contains the "gears". The shaft just below them is the "Main Shaft" or "Axle Shaft". This contains the "pinions". Some of the gears and pinions are connected to the shaft so that they are locked to the shafts rotation, others are allowed to spin freely on the shaft. Located on a rod just above the gears are three shift forks (note: they are numbered right-to-left, 1-3). Connected to "Shift Cam Drum". These forks move two of the gears (4th and 5th) and one of the pinions (2nd/3rd) into different positions on the shaft. This moving gears and pinion are what cause your transmission to shift gears. This design also enforces sequential shifting. Take a good look at the drum to see how the grooves impact the fork positions. The "Forked Gears": These gears make it all happen. Here's how: 4th gear, 5th gear and the 2nd gear pinion have "Dogs", protruding parts that engage with their neighbor gears' or pinions' "slots". These three are only parts fixed to their shaft, with the exception of the 1st gear pinion, which is actually built into the shaft. By connecting with these dogs/slots, they can transfer power to or from the other freespooling gears to the shafts. 4th "Forked" Gear: This gear has three positions. The left position engages with 1st gear, the right position is engaged with 3rd gear and the middle position is not engaged. 5th "Forked" Gear: This gear has two positions. The left position engages with 2nd gear and the right position is not engaged. 2nd/3rd "Forked" Pinion: You can't see it in this picture, but it's connected to the #2 (middle) fork. It has 3 positions. The left position engages with the 4th gear pinion, the right position engages with the 5th gear pinion and the middle position is not engaged. The Gears:Listed from left to right in the pictures: Middle Drive Gear: This gear is fixed to the countershaft and transfers power to the wheels. Whenever the countershaft and this gear are moving, the wheels are moving. 1st Gear: 1st Gear freespools on the countershaft and is always connected to a fixed pinion on the main shaft. When the engine is running and clutch is engaged, this gear is ALWAYS moving. It has slots for 4th gear dogs to engage with. Since 4th gear is fixed to the shaft, then this causes the shaft to turn. 4th Gear: 4th Gear is fixed to the shaft, but can slide into three positions. The 4th gear pinion free spools on the main shaft. When 4th Gear is engaged, it is in the middle position and the 2nd/3rd gear pinion engages with the 4th gear pinion, to transfer power from the mainshaft through the pinion to 4th gear. 3rd Gear: 3rd gear freespools on the countershaft. It's pinion is fused to 2nd gear pinion, as described above. When the engine is running and clutch is engaged, 3rd gear is ALWAYS moving. When in 3rd gear, the 4th gear is engaged with it to transfer the power to the countershaft. In this case, the 2nd/3rd pinion is in the middle position. 2th Gear: 2nd gear freespools on the countershaft. It's pinion is fused to 3rd gear pinion. When the engine is running and clutch is engaged, 2nd gear is ALWAYS moving. When in 2nd gear, 5th gear engages with it to transfer power to the shaft. Notice that now, 4th gear sits as it does when in neutral, connected to it's freespooling pinion. NOTE:The infamous 2nd gear problem is due to a poor contact area between the dogs on 5th and slots on 2nd. In these pictures, the culprit washer has been moved to the left side of 2nd gear, allowing better contact of the dogs and slots. 5th Gear: 5th Gear is fixed to the shaft and its pinion is freespooling. When in 5th gear, the 2nd/3rd pinion engages with the 5th gear pinion to transfer power to the pinion and then to the gear. Additional Info: About Neutral and the Neutral-1st gear shift: In addition to the popular 2nd gear problem, there has also been a number of 1st gear problems with this transmission. The cause is due to how the gears behave when in neutral, and how that effects the shift into first. When the engine is running and clutch is engaged, and the transmission is in neutral, 1st, 2nd and 3rd gears are freespooling, but their pinions are fixed. Thus, each of these gears is spinning on the countershaft, though the countershaft is not spinning at all (remember, the countershaft and wheel have a hard connection, if the wheel is stopped, the countershaft is stopped). Since 1st gear is so large, it has a lot of momentum, disengaging the clutch and shifting into first causes the non-spinning 4th gear to engage with the spinning 1st gear. This causes the shifts to be hard. This is why there is a loud "thunk" when shifting into 1st from neutral. To make it worse, the bike is shaft driven; on chain and belted bikes, the chain or belt will bounce to absorb some of the shock. The way to avoid this is to wait several seconds after releasing the clutch to engage 1st gear. This will allow the gear to slow down enough or stop, so that the shift will be less brutal. 4th Gear-5th Gear dead spot: Someone a while ago was talking about a dead spot between 4th and 5th, that felt much like neutral If you look at the pictures, you will see that the there is no difference between the positions of 4th gear and 5th gear when you are in 4th gear, 5th gear or neutral. It is the movement of the 2nd/3rd pinion that differentiates these gear positions. When you shift from 4th to 5th, you are actually passing through neutral. Why the shifts for other gears are so smooth: The reason that the shifts from all the other gears are so smooth is because whenever the bike is moving (thus, the countershaft is spinning), every gear on the shaft is spinning as well. This allows the dogs to engage with a softer impact, making the shift smoother. How a broken or bent shift fork could ruin your day: If a shift fork were to break or bend severely, this could cause two gear ratios to be engaged at the same time. These forces would work against each other immediately, causing the gear box to lock up or grenade. In either case, you're flying through the air before you have a chance to realize what happened. It's for this reason that being easy on the shifter is so important. It is the force of your foot combined with some springs that cause the shift cam drum to rotate and move the forks. About these photos: I bought this XS11 for $300 with the knowledge that I would have to rebuild this transmission. This is a task that I have never done before. This is the second time I have rebuilt this transmission in the month that I have had the motorcycle. The first time I tried the "black and decker fix", however it only fixed 2nd gear, 1st gear actually got worse. 2nd was also hard to shift at this point. So, I bought brand new 1st, 2nd, 4th and 5th gears as well as the #3 shift fork. 3rd gear was okay. This time the process went much quicker then the first time, you can see from the color of the new parts that they haven't seen much oil, heat or pressure yet. Please feel free to email me with any questions or comments. If any information here is incorrect, please inform me and the website owner. Steve Borenstein: rifraf@mac.com

Click on any picture to load larger and more clear image. 1st Gear:4th engaged with 1st, 5th not engaged. 2nd/3rd pinion is in middle position, freespooling 2nd and 3rd. Neutral: Neither 4th or 5th dogs engaged. 2nd/3rd pinion in the middle, contacts freespooling 2nd and 3rd. Not that this is the only case in which no dogs are in contact with any slots. SEE NEUTRAL-1st GEAR PROBLEM EXPLANATION 2nd Gear: 5th Engaged with 2nd, 4th in middle position. 2nd/3rd gear pinion in middle position, in contact with 2nd 3rd Gear:4th Engaged with 3rd, 5th not engaged. 2nd/3rd gear pinion in middle position, in contact 3rd. 4th Gear:4th and 5th Gear not engaged. 2nd/3rd gear pinion engaged with 4th gear pinion 5th Gear:4th and 5th not engaged. 2nd/3rd pinion engaged with 5th gear pinion.