CV front drive shaft *fix* 03+ 660 Death wobble
*Update, this is considered the "Death wobble"*
My (03+) Grizzly 660 had the famous worn out splines on the engine side coupler splines and engine side drive shaft splines, on the front CV drive shaft.
If you dont ride in lots of mud and water, you probably wont have to ever worry about this happening.
For those that dont know, 03+ Yamaha switched from u joints to a CV joints for the front drive shafts. There is a spring on the engine side of the shaft (diagrams show diff side, its a miss print) pushing the shaft towards the coupler in the diff. There are three problems with this.
1. When the frame twists and bends as you move, the shaft will move slightly against the spring and into the engine coupler more (whether the frame actually ever twists enough to make this move is unknown). As the shaft moves inside more, it pumps air and grease out of the coupler and long rubber seal. When the frame switches back and the shaft pushes back towards the front diff, the coupler then pumps (sucks) water and mud from the current mud hole into the coupler from the seal, rusting and wearing out the splines at a enormously fast rate.
2. Because the shaft does not sit fully in the coupler (extra splines sitting out), the long rubber seal (mounts onto the coupler) does not rest against the housing of the CV joint on the shaft, but instead it rests on the splines on the shaft. This would be fine if the seal was designed for it, but its not. The seal is cut perfectly round inside, but your splines have multiple bumps (being why they are splines), causing the seal to not actually seal, but instead just sit there for the ride and allow water and mud to pass right between the seal and the lower portions of the splines as soon as the grease that is making up for the seal washes away. One again, rusting and wearing out the splines as a enormously fast rate.
3. Because the shaft inside the engine and inside the front diff were designed larger to have a large diameter yoke for the u joints to attach to, when Yamaha switched to CV joints and couplers, the couplers had to be larger in side. This resulted in a large diameter splines because Yamaha is too lazy to remake the engine shaft and diff shaft to properly accompany a properly size coupler and splines for the drive shaft. The diameter is almost as big as the length of the spline. This causes a automatic increase in the amount of "orbit" that the joint has from factory. As soon as there is some mud or water inside, this built in orbit increases the amount of force wearing on the splines.
These two pics (shown without the long rubber seal) both show how much extra splines are exposes and not used in the coupler. This is a 1/3 of the total amount of splines on that end of the shaft, resulting in the diameter of the shaft being just as big as the length of splines inside the coupler.
My camera does not show enough detail to bother taking a picture of the wear, but the splines left inside the coupler were so worn that the ends of the splines were already starting to twist, as it was soon going to strip out the spline.
If i pulled my shaft to one side, i could push it about a inch (1") to the other side. Thats allot of play, the orbiting CV shaft actually wore a mark into the belt air intake pipe above it.
Over priced OEM parts up here in Canada was going to set me back $100 per coupler, and $515!!!! for the shaft!!! That would be over $600 to fix yamaha's F-up! Well, there is no way im spending that much over a shaft. I bought a Kimpex shaft for $200, and the OEM engine side coupler for $100.
Now to fix the problem:
I wanted to fix this from happening again.
After looking over HL and google, the best method seemed to be lengthening the engine side coupler by about 1/4" (give or take), so that there would be less exposed splines, reducing the orbit and allowing the seal to properly seat against the CV housing on the shaft. To do this, you need to either cut the GOOD splines out of the old coupler (the splines in the back of the coupler are still good as the shaft never actually pushed into the coupler more than how it would just sit in there), or cut some splines out of a new coupler, and weld them onto the end of your new coupler.
Its best to take this to a machine shop, if the splines dont line up, or if the weight is off too much you could have serious problems, and is a pain to do if you dont have the right tools (lathe).
Lucky for me i worked at a fab shop over the summer, so my ex boss did it for me! Only took a hour or two, so if you ketch a local fab/ machinist shop while they are not busy it should not cost ya much.
Another option would be to send your good condition (or new) drive shaft to turner, have them lengthen the splines, then send it back. All that shipping + machining sounded like big $$$ to me though.
New coupler, lengthened with 1/4" of the GOOD splines from the old engine side coupler.
I did take pics of it on the bike (fit together and looks like it will work PERFECTLY!) but i must have rubbed my finger across the lens, as the pics look horrible, and you cant even tell where the actual joint is.
I also had to grind down the seal a bit as it was then a bit too long due to the minimal amount of room i left for the shaft to slide.