engine noise after 20 miles on frwy

[jjjjohnnyg]

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

[mxmikie]

adjust your cam chain

[jjjjohnnyg]

Thanks MXMIKIE

Thanks for your feedback. The cam chain was really loose when I got the bike and was adjusted by the dealer less then 100 miles ago. Any other ideas?

[Clerek]

Your cam chain may be loose again or totally stretched to its max. These bikes are 30 years old, and most things after 30 years don't work like they did when brand new. Check the cam chain again...you may be surprised.

-Rick

[Larrym]

Knocking on Heaven's Door

In the "fluid" service did they replace the oil filter?

The knocking at 4K rpms might be there at lower speeds but you just can't hear it. The local auto parts store prob'ly sells a mechanic's stethoscope which might come in handy now and later too. The stethoscope has the usual looks where it fits in your ears but the other end has a metal rod attached to a diaphragm which amplifies the sound.

Get one of these and listen to the engine along the the crank at each cylinder. Then move up to the head and do the same thing.

Trust your ears and if the noise is there then investigate it further.

If the noise is not there then the source may be anything from fuel system to ignition.

If the noise comes from an internal engine bearing and you drive it at expressway speeds then it may fail at those speeds. More than just an awkward moment.......

[Ivan]

There was also a TSB on these bikes that said they could have a slight knocking sound from 4-5 thousand rpm. The fix was a new advance mechanism, which isn't available any more. The TSB also said that no engine damage would occur from this.

Mine does it, and it is significantly lessened if I run higher octane fuel, but doesn't ever go away. I eventually just got used to it.

Also, if you are a hot rodder like a few of us, and regularly spin your engine up pretty good, the cam chain adjuster can slip loose again. Usually the loose cam chain is more evident at idle though.

[bikerphil]

Any oil thinner than 20W50 might make things knock a bit after it's good 'n hot. Make sure your timing is set correctly. Someone may have tampered with it.

[XSokieSPECIAL]

There was also a TSB on these bikes that said they could have a slight knocking sound from 4-5 thousand rpm. The fix was a new advance mechanism, which isn't available any more. The TSB also said that no engine damage would occur from this.

Mine does it, and it is significantly lessened if I run higher octane fuel, but doesn't ever go away. I eventually just got used to it.

Also, if you are a hot rodder like a few of us, and regularly spin your engine up pretty good, the cam chain adjuster can slip loose again. Usually the loose cam chain is more evident at idle though.

Mine is doing the same thing and I'm finding it hard to get used to.

Is it in the vacume or the mechanical advance?

Maybe something can be modified in there to correct the problem.

When I checked the total advance on mine when I first got it running, it was 50 something degrees. seems like an awful lot. Automotive engines run between 34 and 38.

[DGXSER]

Yep, per the manual 36 degrees for Std models and 31 deg for special models. That was the 78-79 settings. Did not check for 80-81.

[XSokieSPECIAL]

I guess it will be in the centrifugal advance mechanism. There must be a worn stop or something.

Oh crap! More exploratory surgery.

[DGXSER]

Hmmm, Maybe it is hooked to the wrong vacuum source? It should be on the #2 carb body nipple and not on the intake boot. At the intake may be stronger vacuum.

[XSokieSPECIAL]

Nope, it's on the ported vac. source. It only goes that high when the RPM'S go up. Hence "total vacume". (I'm probably spelling that wrong)

[XSokieSPECIAL]

OOPS!!! I meant "total advance"

[TopCatGr58]

Hey XSOkie,

That 50 degrees total vacuum IS CORRECT!!! 52 actually...36 max cent, and 16 for vacuum. What you have to realize is that when you are testing it, there really isn't any load on the engine with it in neutral, so it's sorta like when you're running at cruising speed, the fuel air mix gets a bit lean, and the Yamaha Engineers built the vacuum advance to increase the timing past the max 36 degrees of cent. advance to take advantage of the very lean fuel in that riding situation.

HOWEVER, when you crack the throttle open to speed up, pass, going up a hill, etc. the increase load and more open throttle causes LESS vacuum advance, and so it actually retards back towards the 36 degrees position which is the more powerful timing point for heavier engine loads, richer fuel/air mixes and such!!!
T.C.

[XSokieSPECIAL]

Hey XSOkie,

That 50 degrees total vacuum IS CORRECT!!! 52 actually...36 max cent, and 16 for vacuum. What you have to realize is that when you are testing it, there really isn't any load on the engine with it in neutral, so it's sorta like when you're running at cruising speed, the fuel air mix gets a bit lean, and the Yamaha Engineers built the vacuum advance to increase the timing past the max 36 degrees of cent. advance to take advantage of the very lean fuel in that riding situation.

HOWEVER, when you crack the throttle open to speed up, pass, going up a hill, etc. the increase load and more open throttle causes LESS vacuum advance, and so it actually retards back towards the 36 degrees position which is the more powerful timing point for heavier engine loads, richer fuel/air mixes and such!!!
T.C.

OK, I saw that that spec was with the vac advance disconnected.

I've been searching around to see what TOTAL ADVANCE was supposed to be. Thanx for clearing that up.

I do understand how the advance systems work.

What I don't understand is why the engine makes that unnerving clattering noise between 4 and 5 grand in high gear. That is cruising RPMs for me on Oklahoma country roads.

It only does it after it's warmed up to normal op temp.

If it is normal engine noise I will try to ignore it, otherwise I would appreciate some help diagnosing and repairing it.

THANX

Greg