Something snapped! A diagnosis.

[BA80]

The sound may transfer to the middle drive area from wherever the problem is.

Might be a good idea to see if the u-joint is turning when things are slipping with the wheel on the ground.

That would say for certain if it's before, after, or in the middle drive.

[mack]

noise

He says the noise is around the middle drive though. The only things in that area are the U joint itself and the drive shaft spines, the middle drive itself, the middle drive gear assembly and the countershaft drive gear lower down. Hopefully the last two aren't the issue but the countershaft drive gear can be replaced w/o spliting the cases. I'm not aware of anyway to work on the middle drive assy w/o splitting the cases. Hopefully, it's the drive shaft splines so pulling the rear wheel may be inevitable. Should be done anyway to ensure the final drive/drive shaft has been greased. But one thing at a time. Lets find the source first, fix that, then talk him through the required preventive maintenance aspects.

[BA80]

It most definitely seems as tough the problem somewhere between the final drive and the rear wheel.

If it were me I would pull the rear wheel and inspect the splines and the cushion drive, then pull the final drive and inspect......ect. ect.......until I found what's broken.

[skids]

Hey Mes how many bolts are there around the cap of the middle drive? Three or four? I can't tell from the pix. I bought a middle drive off fleabay that was wrong as it only had holes there for three bolts. Same symptoms as what you had and are having. Sometimes it worked and other times it wouldn't "catch".

[mack]

Close

Well Mes, your getting close to solving this riddle. As suggested, pull back the boot and diconnect the four bolts at the drive shaft connection. Start it up and listen to see if you still have the noise. If not, life is good.Probably the U-joint drive shaft connection. If so then you need to pull the middle drive off. Life can still be good. Start it again and see if you still have the sound. If not then life is good still. A middle drive swap is all thats needed. If you still have the sound while running in gear then life just took a down turn. It's most likely the middle drive gear and not the drive itself. This would not be good.

[WMarshy]

Ok, so... The bike changes through all the gears, no problem. A good sign.

But the drive is not being transmitted to the rear wheel. The videos make that very clear and were well worth posting. There is not even enough oomph to make the bike move.

So, engine is running. Power is going through the clutch and the gearbox, hence being able to change through the gears. You would not be able to scroll through the gears like you did if the gearbox were static.

The problem is that the drive is not reaching the rear wheel.

You really must remove that middle drive. Then you will be able to check the drive, and the drive shaft, and the rear wheel gearbox. You will also be able to check the gear that the middle gearbox actually connects up to (advice on that once you have the middle gearbox off).

The middle gearbox is held on by Allen bolts. When removing the middle drive cover, you will have removed a long bolt which is on the left of a pair of bolts at the bottom of the cover. That is one of the middle drive bolts and will need to be removed with the others.

Get that gearbox off and then report back with pix and viids.....

Although I agree with everything you said, I would not recommend jumping right in and removing the middle drive without pulling back the rubber boot and looking at the u-joint first and trying a few other things. Ya have to pull it back to disconnect the middle drive from the drive shaft yoke anyways, might as well do it now. With your symptoms if it was a u-joint I'd expect it to be completely failed and obvious so pull back the rubber boot and inspect it... process of elimination.

With the rubber boot pulled back put the bike in gear and rotate the wheel by hand and observe the u-joint. If the shaft/u-joint isnt moving then its a problem with your final drive. If the shaft rotates then your back to the middle drive. Listen for any noise while doing this. A healthy drive train should only have 3-4 inches of backlash (tire travel) before it engages all the gears and crank shaft. Only noise I hear when I do this on my bike is a slight click from the starter clutch...

Do that and let us know what you discover.

[cajun31]

get the manual

Go to catatonicbugs web site and download the manual. there are step by step instructions on how to do some of the things we are all suggesting. Here is the link for his page http://www.ringler.us/family/mybike.html.

I know you are feeling overwhelmed, anyone would be, and everyone is throwing one suggestion after the other at you. If you understood a little more about how the power of the engine is transferred through the primary gears through the middle drive assembly through the drive shaft to the final drive then you could begin to see why everyone is so unsure as to what the specific problem is. I believe everyone and you especially is hoping that it is something simple rather then the more involved problems. You are going to have to bite the bullet and work your way from the back of the bike up to the middle drive gear and as James suggested you will probably have to remove the middle drive assembly if the problem is not found in the drive shaft, u joint or final drive. The manual will help you as you proceed. A lot of reading but like I said before time is something you have without spending a penny. As you look at some of the illustrations in the manual you will begin to develop ideas as to what could be wrong from what you are hearing a seeing. I am not ruling out anything yet.

[BillyRok]

I didn't see anything about miles on the bike, how long you've owned it, or drive train maintenance. Seems if it was clutch or tranny you wouldn't be able to run up and down through the gears like you did. Here is a thread about middle drive removal, post #7 shows the 7 allen bolts you need to remove (although one is already removed in the pic) and the flange on the right side that connects to the universal inside the big black rubber boot. http://www.xs11.com/forum/showthread...e+middle+drive

I'm wondering if the splines on the drive shaft aren't almost completely gone due to lack of greasing it? I would start at the back end and drain the oil from the final drive (19 mm drain bolt just like middle drive) and then pull the rear tire. Then you can unbolt the final drive (4 bolts) and be able to see the splines on both the input and output side of the FD. Now you can see the end of the drive shaft inside the swing arm to check those splines. Removing the drive shaft is pretty easy, you can loop some wire, twine, etc. up around the shaft past the splines and yank it out. Now you'll be able to see the front splines where the drive shaft mates up with the universal which bolts to the middle drive flange you saw in the picture above.

The 4 bolts holding the universal to the middle drive can be tough to remove, you may need a second pair of hands to hold a punch through the middle of the universal (be careful how/where you insert it) and have somebody hold it to keep things from turning while you break those 4 bolts loose.

That's the method I used to take mine apart before, but somebody else might suggest first unbolting the 4 universal bolts while everything is still put together and then working forward as described above. We're all interested in what you find, curiosity has been peaked...keep at it!

[Eveready1100]

Personally, I'll put my money on the driveshaft being shagged.
With the bike on the centrestand, the shaft will be in a different position to the riding position, so may have enough engagement in that position to spin the rear wheel.
When on the ground, it gets into the most worn position so no drive.

It'd be the easiest thing to check, too.

[James England]

Ok, so... The bike changes through all the gears, no problem. A good sign.

But the drive is not being transmitted to the rear wheel. The videos make that very clear and were well worth posting. There is not even enough oomph to make the bike move.

So, engine is running. Power is going through the clutch and the gearbox, hence being able to change through the gears. You would not be able to scroll through the gears like you did if the gearbox were static.

The problem is that the drive is not reaching the rear wheel.

You really must remove that middle drive. Then you will be able to check the drive, and the drive shaft, and the rear wheel gearbox. You will also be able to check the gear that the middle gearbox actually connects up to (advice on that once you have the middle gearbox off).

The middle gearbox is held on by Allen bolts. When removing the middle drive cover, you will have removed a long bolt which is on the left of a pair of bolts at the bottom of the cover. That is one of the middle drive bolts and will need to be removed with the others.

Get that gearbox off and then report back with pix and viids.....

[ViperRon]

I saw the videos and they give me a different perception than I first had. I thought the drive train would bind up under power. What yours does is totally break loose no resistance. Before you get into the engine can I get you to verify one thing for me. You may have done this but if you have engine off put in high gear key off tilt on stand and see if you can by hand forcefully rotate the rear wheel. The other way would be to take the rubber boot loose to see the U joint and run the bike in gear and see if the U joint is spinning. I may have missed you testing this previous but with the problem getting worse and as little noise as I hear it could be issues with the final drive.

[mesmeridicus]

engine was loud in videos so I could not really here the clunking stuttering you are describing. May just be me I don't know. Very strange though.

By stuttering I mean the bike is trying to move forward a bit, not any particular sound.

Clunking (grinding) is definitely less pronounced today when I started her back up. I don't know why.

Main symptom is, essentially, bike will not move in gear. Shifts through gears fine, and at one point I even heard that normal clacking sound one often hears when downshifting from second to first with these bikes, so something is moving down there.

[mesmeridicus]

engine was loud in videos so I could not really here the clunking stuttering you are describing. May just be me I don't know. Very strange though. Looks like it is shifting through the gears ok though. I found this listing on Ebay http://www.ebay.com/itm/1978-Yamaha-...6c06d6&vxp=mtr

Might want to grab it as a buy it now just in case you need anything from it. What happens if on center stand and you put in gear and try to hold the rear wheel still? How much resistance is there? I notice when not on stand that you have absolutely no torque at rear wheel to even cause you to lose balance. I am hoping that something has not happened to your primary. If that is the case and not the transmission then you are in for more of a job then I would think you would want to tackle.

Hard to say from video.... could still be a number of things.

Thanks, I may jump on that tomorrow.

My primary? Primary input shaft for gearbox? Jesus, worse than the transmission?

Wonderful.

[cajun31]

another cheap part

you might be interested in: http://www.ebay.com/itm/1979-Yamaha-...c5d8fa&vxp=mtr

[cajun31]

watched the videos

engine was loud in videos so I could not really here the clunking stuttering you are describing. May just be me I don't know. Very strange though. Looks like it is shifting through the gears ok though. I found this listing on Ebay http://www.ebay.com/itm/1978-Yamaha-...6c06d6&vxp=mtr

Might want to grab it as a buy it now just in case you need anything from it. What happens if on center stand and you put in gear and try to hold the rear wheel still? How much resistance is there? I notice when not on stand that you have absolutely no torque at rear wheel to even cause you to lose balance. I am hoping that something has not happened to your primary. If that is the case and not the transmission then you are in for more of a job then I would think you would want to tackle.

Hard to say from video.... could still be a number of things.