Motorcycle Repair: 77 Yamaha XS750, engine oil viscosity, worn clutch

Question
Hello Mark,

   I had asked you a question before about my Honda Goldwing, and thanks to your help it's to the point of actually starting! Anyhow, my other bike is a 77 Yamaha XS750. I have kind of a hard question about it, considering you can't see it. When it is idling, it makes a clunk-clunk-clunk sound. It's down in the lower area of the engine or in the transmission. When the bike is put in gear it makes some noise and goes forward. No matter how much I play with the clutch adjustments, it always moves forward when I put it in gear. I also can't seem to find an air filter for it, other than expensive K&N's. Thanks for your time! --Seth

Answer
Hi Seth,

The clucth metal and fiber plates, and clutch springs may need replaced to fix the creeping forwards problem. I suspect warped/worn disks to be the cause of the symptoms.

A tech would need to hear the lower crankcase noises you've described. I suspect it's part of the clutch problem. It may be a broken part or other. One the clutch assempbly is exposed and disassembled, you'll likely find evidence of the source of the noises.

With a 1977 model year, K&N or UNI-filter may be the only options.

I wish I owned a 1977 TZ750!!! <--- My all time favorite MC is the TZ750's.

Always include your email addy so I can return my tech files. My email: mshively1@woh.rr.com

Respectfully,
Mark



Clutch Operation Faulty:

Clutch slipping:

No clutch lever play
Friction plate worn or warped
Steel plate worn or warped
Clutch spring broken or weak
Clutch release mechanism trouble
Clutch hub or housing unevenly worn
Clutch inner cable catching

Clutch not disengaging properly:

Clutch lever play excessive
Clutch plate warped or too rough
Clutch spring compression uneven
Engine oil deteriorated
Engine oil viscosity too high
Engine oil level too high
Clutch housing frozen on drive shaft
Clutch release mechanism trouble
Clutch hub locknut loose