Knock, knock, where's the knock?

[gsJack]

Took another ride yesterday to listen to it and it wouldn't be too bad to just ride as is but still afraid it might breakdown and leave me stranded so same reduced speeds and revs and kept it close to home.  Picked up a cheapo mechanics stethoscope from Harbor Freight while out and went home to listen to it with scope while hot.

Very interesting, listened with scope probe all around both cylinders and heard running noises not heard without scope but didn't hear the knock coming from either cylinder thru the scope but it was always in the back ground.  Pulled both plug wires one at a time with little or no knock thru scope but the loud sharp knock heard when the #2 wire is pulled was there in the background.  Could be it's more related to the big drop on idle speed when running on one cylinder.

Beginning to think maybe the knock isn't coming from either cylinder but maybe it's the counterbalance bearing knock which I haven't checked yet.  Possibly related is oil leakage, I had a minor drip on garage floor from the left lower housing that was gone after I put it back on with Permatex.  But all of a sudden the oil is dripping quite a large amount from the right side cover and when I looked underneath there was a lot of accumulated minor leakage on the bottom of the cover and adjacent block area so it's been seeping for a long time and just started leaking worse.

I'll probably pull the right side covers the first of the week to have a look around and maybe get them sealed up when putting back on. Still haven't heard from anyone that's experienced the balance shaft knock which I've never heard unless this is it.  Does it knock at idle only or at higher speeds only or whatever, acceleration or deceleration?

[The Buddha]

CB noise will be unrelated to engine load, acceleration and most anything else I would think.
Cool.
Buddha.

[prmas]

It could be bearing knock (CB shaft or Crank) due to low oil pressure. Of course it will be more pronounced as the revs drop and the pressure does too but it should not change side to side with the leads off. Have you tested the oil pressure? If you don't have a pressure gauge but do have some really thick engine oil you could try that to see if the knock is less pronounced. If it is quieter it would confirm excessive bearing clearance somewhere.I don't remember from earlier posts if you said that it changed from cold engine to hot or not. Again, obviously it should be less noticeable when cold and the oil is thick than when hot and thin.
As for the oil level check, the standard test for oil level in a car engine is: run the engine until normal oil temperature is reached (drive normally for at least 20 minutes), turn off the engine, wait exactly five minutes and then dip the oil with the car level. This is specified by all engine manufactures to the best of my knowledge. 

Macka

[gsJack]

CB noise will be unrelated to engine load, acceleration and most anything else I would think.
Cool.
Buddha.

Agree on that Buddha but I'm mostly still wondering at what speeds the balancer bearing would knock.  My knock is only at idle up to 2k rpm or so and goes away after that.  It sounds same to me at cold startup as it does hot.  Can ride for miles without hearing knock if I don't slow down to a stop.  It did sound not quite as loud after I put the left covers back on and filled it with 15-40 replacing the 20-50 I had drained to pull the left covers, also put in new plugs at that time too.

[gsJack]

To recap a bit more than in post to Buddha above the 20-50 oil I drained last week was put in late last summer when I heard some piston slap and it quieted the piston slap at that time, it only had about 1k miles on it.  I filled with 15-40 a lighter oil after draining to check goats and starter drive on left.  Doesn't seem that going back to a heavier oil now would change anything but after I pull the right covers to inspect inside next week and fix oil leak I can refill with any weight oil to test.

Don't have an oil pressure gage and don't think it's a problem but I could get one.  When I had the top cover off to check CCT, cam timing, camshaft side play, and valve clearance I cranked the engine over with plugs out and oil flow to the top seemed quite good yet although not as good as it was 100k miles ago.  The oil pressure light did not go off when running at reduced idle speeds of 6-700 rpm on one cylinder when pulling plug wires to test.

A big end rod bearing knocks most when revving up and backing off not at idle, a main knocks under load and can also be heard at idle if bad, but I've never heard a balancer shaft bearing knock before.  How heavy of an oil would you try to silence a possible balancer bearing knock?  I've read a bit on the balancer thing and it seems the bearing failures might be due mostly to blocked oil passages to the bearings and that would take a teardown to check out.  If I don't learn anything from removing the right side covers I could fill it with heavier oil to test next.

It could be bearing knock (CB shaft or Crank) due to low oil pressure. Of course it will be more pronounced as the revs drop and the pressure does too but it should not change side to side with the leads off. Have you tested the oil pressure? If you don't have a pressure gauge but do have some really thick engine oil you could try that to see if the knock is less pronounced. If it is quieter it would confirm excessive bearing clearance somewhere.I don't remember from earlier posts if you said that it changed from cold engine to hot or not. Again, obviously it should be less noticeable when cold and the oil is thick than when hot and thin.
As for the oil level check, the standard test for oil level in a car engine is: run the engine until normal oil temperature is reached (drive normally for at least 20 minutes), turn off the engine, wait exactly five minutes and then dip the oil with the car level. This is specified by all engine manufactures to the best of my knowledge. 

Macka

[The Buddha]

The CB bearing if it went bad should knock at all revs.
I suspect the thing is a cam shaft side drift.
You have even about .25mm you could hear it. By .5 mm on line it was loud and miserable.
Cool.
Buddha.

[Blueknyt]

The CB bearing if it went bad should knock at all revs.

it did not on mine, the higher revs got quieter, the right side bearings on the CB shaft were done, i took the right side cover off and cranked the engine over with the starter (plugs out) and was lookin for ANYTHING and found the end of the shaft wobbling.  hence when i go to rebuild this motor, im looking to go with a set of 78mm pistons and send everything to falicon for balenceing to get rid of the CB shaft.

[gsJack]

I had the camshaft end play knock at one time on both my 97 and this 02 GSs Buddha and know what it sounds like.  It's at a completely different frequency from my present knock on the 02.  My present knock is at a frequency a crank bearing, balancer bearing, or piston knock would be and the cam knock is at a much lower frequency.

I found adidasguy's thread on Rebuilding Junior and Junior's problem was a knocking balancer shaft bearing that went real bad.  Found this pic showing the end of the balancer shaft can be reached by pulling the right side lower cover.  His video shows him shaking a very worn balancer shaft with that cover off and that's about the only knock source I suspect now that I haven't been able to check out yet so when I pull that cover the first of the week to fix a newly developed oil leak I'll check it out, thanks to Patrick:

  http://www.youtube.com/watch?v=Atq4nKfh7kg

[gsJack]

Thanks for the confirming post Blueknyt it arrived while I was posting to Buddha.  I've been looking for that input since I started this thread.  At 81 yo now with growing physical limitations I'm quite reluctant to tear into anything without a some hope of it being worthwhile.  I think my family would be delighted if I couldn't get it fixed once more.   

[Blueknyt]

yup, that video is exactly what i have on that engine, its a knock at low end, load doesnt change the sound, RPM does, it stablizes at higher RPM, but lower RPMs it flops and bounces. but it sounds like a crank main would coz the CB shaft is almost as heavy as the crank.   you could run the engine without a CB shaft and just plug the oil holes but the vibrations would break engine mounts.

[The Buddha]

It gets better at higher rpm ? Ok that's educational for me. The thing should have bearings you can replace on the end, not one where you need to split the cases. For all the trouble it causes it should be replaceable quick. That way they can sell more parts.

Cool.
Buddha.

[Blueknyt]

the right side of the CB shaft has a bolt and washer, then there is a machined spacer that is the bearing surface of the shaft, the other end is machined AS a bearing surface.  If your gonna split the cases, unless you have parts ready to drop in (I had 3 engine worth of parts, way back when) might want to consider sending the crank,rods,pistons w/pins and rings to a company like falicon for balancing, then you block off the feeder holes for the CB shaft (super easy to do and very reversable) let the CB shaft sit as a door stop and never have to worry about it again.  the down side is it might be a touch buzzy at a rpm, the up side is now your not bleeding off already limited HP to spinning a chunk of metal that weighs almost the same as a crank and putting it to the rear wheel, and you have less holes to bleed of needed lubrication.

[The Buddha]

We should machine the case and the CB shaft to take a ball bearing.
We prolly cant machine the case much. But The shaft should be ...
I dunno how but more bikes dont have CB. I think its a stupid idea.
Cool.
Buddha.

[john]

I am watching this thread with interest.  Sounds like the cause may be found soon.

[gsJack]

My 2 Honda 400 cc twins had balancers that were chain driven rather than gear driven like the GS, they had 2 cyls moving up and down together rather than one up and one down like the GS.  Never had any trouble with those or with my 650 and 750 Honda fours that didn't have balance shafts.  Put about 98k miles on a CM400 and when badly rusted from winter use I gave it to a friend that was starting to ride again and it had over 100k miles when I last saw it.  No trouble with those balancers or their chain drives.

Makes me wish my GS balancer had a chain drive I could temporarily disengage to confirm my knocking problem.  Would be tempted to leave it disengaged if that did it, would have to pull engine and split case to disengage it's gear drive or to replace worn bearings.  It's been a long time since this old man went screaming thru the mountain twisties, just want to putt around at legal speeds and smell the roses now for another season or two. 

Beautiful day today so I'm taking my bride of 62 years to see the hundreds of Herons that nest just south of us annually so I won't be pulling the right side cover at least until rainy tomorrow.

[gsJack]

Strike three?  Pulled the right cover and tried to shake the right end of the balancer shaft and couldn't budge it.  Well I'm a generation older than Addy who shook Juniors' all over the place so I pulled the plugs and cranked it over spinning the big washer and bolt on the end of the balancer shaft around and around and it didn't move sideways, up and down, or any other way except around.  Blueknyt reported his wobbled when spun with a bad balancer bearing.  My right side balancer bearing looks as good as the goats and starter drive check did on the other side and the CCT, cam timing, valve clearance, and side play check did on the topside.

But wait a minute, I'm hearing a very light almost inaudible knock coming from nearby while sitting on the right and spinning it over.  Almost missed it.  Covered the #2 plug hole with my finger over a rag and it was gone.  Couldn't hear any light knock like that over on the #1 side while spinning it over.  Remembered it was when I pulled the #2 plug wire while at idle that I heard the very loud sharp knock that was much louder than when both cylinders were firing at idle.  Me thinks there must be a gremlin in that #2 cylinder taunting me?

[Blueknyt]

sticking valve or worn piston pin?

[bombsquad83]

Or the rod bearing at the crank on that piston?

[gsJack]

Don't think it's a valve problem Blueknyt, it still runs too good and smooth (for a GS) to have a sticking valve.  While pulling wires to check for piston slap/knock it would run and keep on running on one cylinder at idle with the idle speed dropping from 1100-1200 rpm to about 600-700 rpm and was the same for either cylinder.  Still had a nice loud clear compression pop yesterday with my finger over the plug hole cold until I damped it with a rag.

Could be the piston pin you suggest or the cracked ring land or broken rings suggested by prmas way back on the first page.  The fact it was running good as ever when something happened all of a sudden and never reversed hot or cold since suggests something broke.  Sounding the same now knocking hot or cold at idle up to 2-3k rpm only eliminates piston slap/knock since it doesn't change at all as it warms up.

Well confirming it wasn't the balancer bearing knocking which would have required pulling the engine and splitting cases which I wasn't even considering doing leaves me pondering whether to maybe pull the head and pursue it further.  It's possible to pull the head and cylinders and replace pistons/pins and rings and hone the cylinders if the rod big end bearings feel ok I think.  I remember you prefer doing a complete job fixing up an engine but I'm not up to that now.  If it was late fall instead of spring I'd probably be out there now pulling the head instead of looking thru the want adds for bikes.  At 100.5k miles I really have got my money's worth out of this one already.

[piresito]

So...which bike you're getting now?