Topic: Very Strange Engine Rattle

[billstron]

hello all.  I have a '78 550, and a rattling noise emanating from the left hand side exhause. 

I just did a periodic maintenance -- point, valve lash, brake inspection, clutch adjustment, and cam chain adjustment.  The cam chain adjustment is always a bit tough because the damn thing doesn't self adjust like the manual says.  I have resorted to tightening the lock nut while holding the adjustment screw firmly in the counter clockwise direction.  It is a very imprecise adjustment. 

Back to my problem.  Post maintenance, I have a rattle coming from the engine.  When I first started it up, I thought the cam chain was loose, and tried the above procedure to adjust it again.  I no longer hear a noise coming from the engine, but I now hear one coming from my right hand side exhaust pipes.  The noise is barely noticeable at idle, but at higher revs it gets more noticeable. 

So here are a few of my ideas about what is going on.  Maybe the cam chain noise and the exhaust noise are just coincidental, and maybe I just have some loose rust in the pipe or something.  My other idea is that the cam chain is still loose, or I did something wrong with the valve lash.  My last thought is that I don't know WTF is going on (this is probably it).  What do you think?  Thanks!

[nickjtc]

Did you synchronise the carbs? Sometimes out-of-sync carbs can create interest harmonics with the internals of the noisy bits.

[billstron]

No, I didn't sync the carbs, and I didn't even think about that as an answer.  I haven't made any carb changes for a while, though. 

[billstron]

Well... to finish things off.  It turned out that the noise was coming from the exhaust pipe.  I have something rattling around in #4.  The worst part is that #4 is the best looking of my pipes.  I guess it is time for a new exhaust.  I have wanted to put a 4-1 on there since I bought it.  I have a pretty good reason now. 

On a side note.  it turns out that I wasn't adjusting the valves correctly.  You turn clockwise to tighten.  Makes sense, but I thought it was the other way around. 

[upperlake04]

Bill - changing the valve lash will affect the breathing characteristics of your engine which will require (for perfection)  a new carb synch.

[OldSchool_IsCool]

hello all.  I have a '78 550,
...
The cam chain adjustment is always a bit tough because the damn thing doesn't self adjust like the manual says.  I have resorted to tightening the lock nut while holding the adjustment screw firmly in the counter clockwise direction.  It is a very imprecise adjustment. 

Bill,

Did you ever solve the cam chain adjustment issue?  Mine does the same thing, ('77 550) never tightens, just turns and turns and turns.

[billstron]

OldSchool -- I solved the cam chain adjustment issue by idling the bike while turning the screw and listening for less noise and feeling for more resistance.  After I got a feel for about where the adjustment should be, I used the procedure in the manual (with the engine off) to set it.  I hope this helps. 

[OldSchool_IsCool]

Thanks Bill!

So idle the engine, back off the lock nut, turn the adjuster screw to reduce the chain clatter, shut 'er down and follow the instructions in the manual until the lock nut is tight?

[billstron]

That is exactly what I did.  I cannot guarantee that you won't break the bike with this process, though.  I wish someone else would chime in here.  Where is TwoTired when you need him   

[svenD]

when I do the ajustment on my 550,I find it helps activate the ajuster if igently turn the crankshaft acouple of degrees or so to and fro,after loosning the locknut of the ajuster .With alittle practice,you can feel the chainslack.otherwise I do it by the book.550 K1 engine.