Rear troubles

[superman6262]

Awite im hoping someone out there can help me. I flipped my bike the other day and it rolled into a ditch. Now the front tires turn and the rear ones dont. They will roll but i dont have four wheel drive. Now im riding EURO style...... front wheel two wheel drive. Any thoughts......maybe a broken axle. The mechanic at my bike shop said this was impossible since the wheels still turn.......we lifted the bike completely off the ground and the only thing turning was the front two wheels when we gave it gas. helllllllllllllllllllllllp please

[Jake]

Your mechanic is right, but only sort of right. It shouldn't be able to happen unless you also describe to him massive engine oil loss, binding, catching, or deafening grinding noise. But sometimes in the repair buisness there's "non-standard" failures, that no experienced technician will dare to give you his guesses at, even if he has them. (New techs love to guess at such things, until it comes back to bite them a time or two and somebody looses a good customer, or better yet gets sued over it.)
Seeing as how I'm in no way responsible for billing, (quoting in particular) or otherwise actually fixing the bike for you, here goes nothing...

First, the final shaft inside the engine case is just one shaft. If you broke that, I won't say it couldn't be otherwise, but first, I think the front is more fragile than the back, and second, I think you'd be loosing tanker loads of oil from the engine. Assuming thgat this is all good, you have narrowed it down to something inside the swingarm or inside the rear axle/differential assembly.
Recommendation one. Jack up the rear axle. Take the filler cap off of the rear differential. Rotate the rear tires and see if the crown gear rotates with the wheels. If not, you are more likely than not looking at failed splines in the crown gear and axle, but it'll have to come apart to see for sure. The good news is this. If you jack up the rear most part of the frame, block the trailer hitch (by adjusting the jack height under the frame) so the swingarm is dropped, but there is ZERO pressure against the shock, you can remove the shock bolt. Take off the tire, the hub (and it's "washer thing") the axle tube, the diff skid plate... basically work yiour way in until you get to the differential cover. The cover AND the crown gear can be slid right off of the axle for inspection with about a third of the work that it takes to haul the differential out as an assembly.

Recommendation number two. (only applies if the crown gear appears to still be splined properly to the axle) Jack the rear axle up, loosen a clamp on the boot between the engine case and the swingarm tube, and pull the boot back enough to see the universal joint and final shaft. turning the back wheels by hand will do one of two things. It will rotate something there or it won't. I'm assuming it won't, since my gut tells me the failure will be somewhere in the swingarm/back axle, but assumptions get you in trouble and it's an easy enough check. If turning the wheels turns the universal joint assembly (assuming it's not broken) then the trouble will have to be in the engine. If the universal joint does not turn, the problem has to be in the driveshaft or the pinion area of the differential, and you'll have to dismantle the swingarm in order to inspect it adequately.

[superman6262]

Dam jake your good. We did check the boot behind the engine and the universal joint and final shaft are spinning they just arent turning the back tires. so im with you on the first choice. it's gotta be the rear axle or something in the final gear. i got the bike up and im working my way in.... i didnt have a big enough socket to take that hub nut off i think its 20mm...... so im guessing once i get that off and work my way in ill find my lil surprise. Hey speaking of which that boot behind the engine case and they swing arm tube is torn on my bike. My question is.....is it possible to change it coming in from the rear since im already working back there, or is my ignorant mechanic wrong( he told me the engine had to be rocked forward. I dont see why i cant replace the boot by coming in from the rear since im already workin back there. THANKS FOR YA HELP MAN!!!!!

[Jake]

The socket you need is 30mm. 1/2 drive six point deep well is my favorite weapon, YMMV

The mechanic is right. The easiest way to change it (and I've tried them all) is to unhitch the front differential and the three motor mounts, and shuck everything forward. The hitch is that you need to have a pretty good "handle" on the overall machine to pull it off. If you've never had the engine or front driveline out to have a hands on idea of what to pull, shuck, shift, or otherwise relocate, and the exact directions to move stuff, it could turn out to be a nightmare too.

There are two other viable options, which I consider better for DIY or casual mechanics, or IF you're tearing stuff down anyhow.

If you're removing the swingarm, you'll need two tools (One is a 17mm allen socket for your half inch ratchet, the other a special socket that can be purchased (expensive), made (time consuming) or done without (pretty butch, but it works). Since the swingarm is off, then obviously you should stick the new boot on while it's separated. Goes without saying almost.

The last method is if you leave the swingarm on the bike, but dismantle the rear axle (or don't), then you can remove the bolts holding the differential housing (and axle housing) to the two sides of the swingarm, move the differenial out of the way, pull the driveshaft and universal joint out of the swingarm tube, then the boot will slide right in between the engine and swingarm fairly easily. Just make note of the orientation of the boot an the clamps and be sure theyre the same when they go back.

One note- While this last method can be accomplished with only the tools supplied in the factory tool kit, you HAVE TO WATCH OUT for is to KEEP YOUR FINGERS CLEAR of any pinch points when lining the u-joint back up. Before you're done, you will cause one of the tires to roll, causing the joint to rotate, and much more quickly than the wheel. If you're lucky, it'll be bad enough to need medical attention, then they can give you good drugs for the pain. Otherwise, it'll not be quite that bad (like mine was), so you'll be condemned to several days of a throbbing finger.

Now that I've scared you to death (I hope), let me say it's kind of like using a skillsaw. You still have to watch out, but there not so dangerous once you know where the sharp spot is.

[superman6262]

Thanks for all the feedback jake im on it!!!!! HHHHHHHHHHHmmmmm i might go the third route if the goods drugs are included hahahahahah. Be cool man