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strange rattle sounds

  • Thread starter Thread starter karlschoen
  • Start date Start date
K

karlschoen

Guest
Hi, I need some help please.

1979 GS 425E, 19,000kms

there is a strange rythmic rattle/knock sound coming from the top right side of my engine. To me it sounds like the cam lobe contacting the valve, but I am unsure.

I adjusted the timing chain so that seams ok. I only hear it @ idle, but not all the time. if I lean the bike to the left or onto the kickstand it is always there, if the bike is centred it only is there sometimes, if I lean the bike to the right it goes away.

the bike runs very well and has ample power. It starts well and this is the only problem. I am wondering if there is some kind of shim, bushing or adjustment for the camshaft and maybe the camshaft is slipping a bit to the left. I know there are shims for the valves but I don't think this is it as the leaning of the bike shouldn't matter.

any help you be great as I am stumped.
 
karlschoen said:
yes of course.
Click to expand...

Not necessarily. I am unsure of this one, as well, but it DOES sound like a bearing is getting oil, but not enough of it.

The best I can come up with is that you may have a partial oil flow blockage, so that you get gravity and splash feed when the bike is upright or on the right side, but it runs away when leaned to the left, leaving the then-physically-higher right side of the engine with insufficient oil.
 
thanks, I will check that out. do you know if the camshafts have any shims or adjustments to stop lateral movement?
 
karlschoen said:
thanks, I will check that out. do you know if the camshafts have any shims or adjustments to stop lateral movement?
Click to expand...

You are thinking that it's camshaft endplay, but there are no thrust bearings or washers that I know of to cure the problem. Maybe someone else knows of some. Some folks have maintained that these engines have cam noise problems related to excess bearing clearance, but that it's not a real problem.

I can relate to your problem, however, because I've got a similar noise on a '79 850.

Question: Is your noise related to heat expansion at all? For example, do you have NO noise at start up (when stone cold), progressing to a pronounced noise when sort of half-warmed up, progressing to No noise again when full hot?
 
hi,

the noise is intermittent. It can occur when the bike is either hot or cold. I took it to a buddies house last night who is pretty knowledgable. He was stumped too but he is the one that found when the bike is tipped on the side stand or to the left it is noisy always, on centre sometimes and to the right it seams quiet.

this is why I was wondering about the cam shifting to the left when the bike is tipped. I have owned this bike for 18 years and it always is a noisy lil bugger but that's normal. this is different. sounds like a marble in a tin can but rythmic
 
karlschoen said:
hi,

the noise is intermittent. It can occur when the bike is either hot or cold. I took it to a buddies house last night who is pretty knowledgable. He was stumped too but he is the one that found when the bike is tipped on the side stand or to the left it is noisy always, on centre sometimes and to the right it seams quiet.

this is why I was wondering about the cam shifting to the left when the bike is tipped. I have owned this bike for 18 years and it always is a noisy lil bugger but that's normal. this is different. sounds like a marble in a tin can but rythmic
Click to expand...

My noise is exactly as you describe, except it behaves as I've indicated in my "question". Even after going away in a full hot condition, the noise will return if I ride through an area or time of day where/when the air is cooler.

The engine is quiet as a mouse when first started cold or when full hot. But when I stop for 10-15 minutes and restart and I get that rythmic knocking so strong I can feel it in the handlebars.

A stethoscope seems to indicate the noise is loudest on the #3 barrel, but it is telegraphed up to the exhaust cam area. My diagnosis is that it's a cracked piston (at the pin boss) or a con rod small end/wrist pin problem. There is far too much clearance somewhere and maybe when the piston expands more than the cylinder barrel, it tends to seize in the bore and the pin/? clearance gets taken up all at once with a "knock". I haven't figured out the side-to-side difference yet.

Why don't you get a stethoscope and see if you can really pinpoint your noise. I might be wrong, but, I too, have spent considerable time listening to and living with this noise and I'm pretty sure mine is not cam end float.

It's interesting that both bikes are '79s, have the "rythmic knock", and the same side-to-side change in the presence.

I'll be interested in what you find out.
 
first thing I ma going to do is check the vlave clearance. I spoke to a bike shop today and they suggested I remove the chrome cam caps and rubbe D shaped plugs in the end of the cam housing then try to move the cam side to side with a screw driver or something just to see if it has any movement
 
make sure your vacuum hose off carb number 3 has a good seal on the petcock. mine cracked and had an air leak and made a loud knocking noise due to that cylinder running lean. sounded like marbles rattling around. once i fixed the hose, it shut up.
 
we did use a stethescope. the sound is coming from the right front cam area.

mine is just a bothersome noise. the is no vibration or lack of performance.
 
I just got back from a 10 K ride.

yesterday we adjusted the timing chain using instructions from the clymer manual. I've never done it before. It still made the noise so I rode it home from my buddies house and parked it in the shop.

I decided to go out tonight for a short ride and the bloody thing ran quiet as a church mouse. I tried leaning it left and right waaay over and nothing. I stopped and started it 6 times....nothing. Now I am wondering if...

1. I am nuts

2. after adjusting the timing chain does it take a short ride to reseat anything or recentre the camshaft or some other wonky bloody thing.

3. both of the above
 
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