looking for expertise

[XSessiveForce79]

my 79 standard is having issues. the jerky feel at low speeds and the growl and vibration at higher speeds have me thinking I have a bad u-joint. but other things come into play previous owner rode this bike HARD.I have thought for some tie that I had way too much clunking going on in the middle drive when dropping into gear from neutral for one. that and the fact there was almost no oil in it.
...anyhow, last year while attempting to get rid of vibration, I switched from my 79 tube rims to- new tires on my 80 tubeless rims. balanced them.NICE but did not get rid of the high speed vibration. I don't believe that my 80 rear wheel mounting to my 79 final drive is going to amount to any vibration

....anyhow, my clutch has also started slipping quite a bit ( hoping to swap parts again with the 80 ? ) swingarm bearings could probably use grease or adjusting...last year I changed the steering stem bearings...they were almost non existent.
SO. any advice,tips , suggestions , heads ups.would be greatly appreciated!
I am hoping to take the '80 parts with lower miles (12k) and replace the '79 parts (that have about 55k )
clutch-middle drive-u joint,drive shaft,and final drive.

last spring it was steering stem bearings,wheels/tires,rebuild the carbs,reshim the valve clearance,and rebuild the brake calipers.
I hope to keep the down time to a minimum.with your help I should be good. I did print off the Drive Shaft service manual and the pages of the OEM book on middle drive removal from Steve's page. Thank you. and thanks again for any advice you XS'ers have to offer.

[BA80]

Addressing the vibration: If you have a middle drive going bad you need to get that fixed before you ride any more. If that locks up so will your rear wheel and down you'll go.

Have you drained the middle drive oil and checked it for metal particles? That would be the first step with that.

The growl you speak of; These transmissions make an unusual amount of noise compared to most other bikes but a middle drive going bad will be a bit louder.

The U-joint; You should be able to pull the swing arm boot back enough to get a look at it. You should also be able to just feel through the boot and see if there's slack in it. If the joint is bad the swing arm or the middle drive has to come off to get it out. I think the middle drive would be easier myself.

Clutch slip; I'll as you the very same question I do all the nubies that come on and are experiencing clutch slip. What kind of oil are you running and are you using any additives? These wet clutches are kinda picky about oil and really don't play well with additives.

Also after 34+ years of being compressed and being abused the clutch springs will get weak and need replacing. I would suggest you do that anyway because the springs are cheap and easy to replace. Barnett heavy duty springs is all I would use.

Most any parts or instruction you might need is right here in this forum. The only dumb question is the one not asked.

[TopCatGr58]

+1 what Greg said. The middle drive does sound suspect, especially with 55k of hard abusive miles with little oil! His advice of looking for metal fillings in it would also apply to the Final Drive as well, but they are much more durable than the middle drive.

If you have a micrometer/dig. caliper, it would be a good time to check the thickness of the 55k frictions....you'll probably find then close to the 2.80 mm min spec vs. the 3.00 mm max spec, and the 12k frictions will probably be very close to the 3.00 max spec, so you could swap them out anyways. Follow the info in the Extra Steel Plate tech tip, just don't bother with the extra steel, just the Barnett springs will be plenty, but DO replace the springs EVEN if they measure within spec length....but I would be surprised if they did!

Yep, dino juice or semi-synth with nothing in the lower API semi-circle part of the seal which would mean NO Energy Conserving FRICTION MODIFYER additives ....which don't play well with our wet clutches.

Inspect the splines on the drive shaft where it goes into the final drive, if it was not serviced properly, you can have severe wear which would then lead to skipping teeth as well. So you may want/need to swap the driveshaft and final drive anyways! Remember the ZERK fitting on the driveshaft/final drive junction does essentially NOTHING, you need to separate to clean/regrease usually at every rear tire change.

While you have the clutch apart, pull the handlebar cable, clean and relube, will make a big difference/easier pull action especially with the newer stronger springs!!

T.C.