engine noise after 20 miles on frwy

[TopCatGr58]

See this technical bulletin from Yamaha!

Click on image to enlarge to make it legible/readable!

The vacuum advance upgrade unit is NOS!

IF it's truly possibly a form of detonation due to too much advance at cruising speed, you might try setting the static timing back a few degrees, or possibly putting a dampener in the vacuum line so that it won't generate as much vacuum at those rpms?? Also, try just diconnecting and plugging off the carb port and riding it to see if it stops??

T.C.

[XSokieSPECIAL]

Thanks TC, that is what I needed to know.

The TSB is what I really wanted to see. I think this is what I'm hearing. That is what I kinda thought it might be from the sound.

I haven't had the opportunity to try it yet, because it's been raining the last few days, but pulling the vac line to the advance diaphragm was one thing I was thinking of trying.

How many degrees do you think I should back the base timing down?

I guess I should just feel it out, huh?


Thanx
Greg

[XJOK2PLAY]

I am getting some significant engine noise on my 1980 XS1100 Special after about 20 miles on the freeway at 65MPH or so. It knocks when giving it gas above 4000 RPMs and almost sounds like it isn't getting oil or could it be the valves? I recently got the bike and had carbs, tires, fluids and complete running service done before driving it. It only has under 12 thousand miles on it and really looks and runs great otherwise. Any ideas?
This is not my first xs1100 and don't remember this noise before but that was 20 years ago!
Thanks
Golden Graham

One other thing you might check, crack open the top oil tube fitting on the back of the motor, start it up, and make sure oil is reaching the top of the motor. If no oil is observed, put the bike on the sidestand, remove the left cover... (engine off). Behind the clutch basket in there you should be able to spot the oil pump driven gear... if you see the gear flat down on the bottom... drain the oil, pull the pan...
I had this happen to me... both bolts managed to work loose and the pump suddenly fell out. Could be a sheared gear... something that's caused the pump to fail.
But, no oil pressure AT ALL should be causing it to be noisy at idle as well...
Mine was! JAT.
Bent valves usually won't even let it start...
I have seen gas leaking from faulty float valves overflowing into the crankcase, deluting the oil... might check that. Any gas puddles on the floor from the airbox after parking? Check oil level in the sight glass, bike straight up for overfull.

If oil looks good, check compression... That'll test valve health.
Cam chain adjustment can be really tricky, adjusters can sometimes be a real PITA, and sometimes they can be a nightmare! I agree with the others here... probable culprit. Even if you did just have it readjusted recently.

Hope this helps you find it. Thought I'd throw in a few of my thoughts that I didn't see anybody else mention.
Good luck.

[tw1980]

I had a similar problem when I first got my bike.I ordered a valve shim kit,adjusted the valves and the noise went away.Only difference was I could also hear it a bit when idling.

Terry

[XJOK2PLAY]

One other thing I might add:

It has been my observation that the 11's are a little "clattery" sounding... especially at highway speeds... but that's pretty normal.

But loud clattering or knocking... that's a different deal there...

Hard to tell w/o being there firsthand...