What could cause a noisy fifth gear on a 1999 Yamaha 650 v star?

Answer 1

Hello. Are you sure it is 5th gear making the noise? The noise is quite possibly a dry and very worn coupling which connects the drive shaft to the pinion shaft in the differential. Yamaha does not put enough grease an this coupling at the factory. Folks think that driveshafts are maintenance free and don't think to check this joint. My wife's 2002 V star 650 Classic experienced a driveline failure at 11,000 miles. The coupling wore down and eventually stripped the splines from the pinion shaft. You can't buy a new pinion shaft, or even a ring and pinion set. The only repair is to order an entire new differential assembly (about $600, as of 12/22/06). Unlike an automobile, which uses a yoke and u-joint to connect the driveshaft to the rear of the transmission and another to connect the diveshaft to the rear pinion shaft, most shaft driven motorcycles only employ a yoke and u-joint arrangement where the driveshaft connects to the transmission. Most modern bikes also have enclosed driveshafts, which are great at keeping things contained, uncontaminated, and lubed. I have a Yamaha Virago 535, a VMax, a 1981 XJ650 Midnight Maxim, and a Royal Star Venture, which have enclosed shafts. No problems at all with those bikes. However, the V Star series utilizes a design that employs an "open type" driveshaft. You can see about a foot long section of the driveshaft spinning as the bike is moving. The design uses a coupling which allows a little necessary movement between the splined rear end of the driveshaft and the splined area of the pinion shaft. The coupling looks like a 3 inch piece of pipe which has splines on the inside. The rear of the coupling slides over the pinion shaft and the driveshft slides into the coupling from the front end. There is a shock spring located in the end of the pinion to keep the driveshaft from slamming into it as the suspension of the bike moves up and down during normal operation. During any rear wheel removal the entire rear differential and the driveshaft must be removed as one unit. Sounds complicated, but in reality, it is a very, very easy process. When the assembly is removed, it only takes a minute to remove the four acorn nuts from the forward housing of the assembly, slide the housing up the driveshaft and inspect the coupling for proper lubrication. Even if you have to grease the coupling joint, it should only take about five minutes to disassemble the housing, grease the area, and reassemble it. The problem is that most folks don't think about it. The design of the differential causes you to think that the front housing is lubricated from the differential fluid. However, it is a totally separate area and requires a moly type grease for the coupling. I have been my own car and motorcycle mechanic for about 35 years and even I didn't think about inspecting that area (until it failed). Now (as well as feeling embarassed) I'm spending big bucks for the part, which I hope gets here soon. I'm just glad the parts failed about a mile from home and not while we were on a trip to another state. I would hope that you take the time to inspect your differential. While you are at it, take a few minutes to inspect your wheel spokes for tightness. The V Star rear wheel seems to like to loosen its spokes every so often. If any need adjusting, make absolutely sure to tighten them in the proper sequence or you will pull the wheel out of round. A spoke torque wrench is a valuable tool to use for this. Good luck.