Three months without a ride, the longest I've gone in my 30 years of riding.  But the horrible winter just past and my advancing years grounded me until Tuesday when I headed out on my first ride of this season.  Only got about 10 miles and when I coasted up to a stop it started to knock, blipped it a couple times and it was a pretty good knock so I turned for home and it didn't knock at all above 2-3k rpm so only heard it at stops.

Started checking it out yesterday. Thoughts were of common GS problems like goats or balancer shaft bearings, I dismissed rod and main bearing noises since I know from 65 years of driving and working on cars what they sound like.  Could be bad piston slap, nearing 100k miles on it I heard some last summer when slowly passing a row of garages coming home hot and a change of oil from 15-40 to 20-50 quieted that down.

Decided to check out goats first after checking compression which popped as good as ever, I'm an experienced finger over the hole test man.    Removed lower left case cover and everything looked good as new.  Rotor tight on crank and all magnets tight as new.  There was about a mm of axial free play of the gear attached to the sprag clutch hub part that I wondered about?  Prabably OK, that thing just sits there with the crank spinning inside it after startup.  All teeth on gears looked good including the little one on the starter motor shaft which can be seen from there.

Wonder now if I should put the left cover back on and fill it with oil again so I can run it to test further or try to check out the balancer bearing possibility first.  Read in a couple posts that I can remove right side clutch covers and reach in and grab the balancer shaft and try to shake it to check bearing, is this true?  Anyone check it that way?  The right side is the gear side of the balancer assembly and most likely first bearing to fail?

Probably take a week to get new gaskets to put it together right but a little Permatex on the left cover should hold to get it going for further checking for now,  I'm not considering pulling the engine and splitting the cases to check bearings, bike is too old with too many miles on it to spend the summer doing that.  Replacement would be better option for me.

Edit: Forgot to mention the knock did sound like it was coming from the bottom end to me and did seem like it was a little louder from the left side but I do probably have the oldest ears on this board.   

Cam chain tensioner is my guess ...
In 6th gear with the plugs out turn the rear wheel while looking @ the cam chain between the sprokets. If you see sag that = tensioner is going.
Cool.
Buddha.

Pull the rotor, my starter clutch was making that nose due to being locked up and jumping, I don't think there was any play in the rotor either


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Quote from: The Buddha on April 03, 2014, 11:25:40 AM
Cam chain tensioner is my guess ...
In 6th gear with the plugs out turn the rear wheel while looking @ the cam chain between the sprokets. If you see sag that = tensioner is going.
Cool.
Buddha.

Put the left case covers back on with a light coat of green Permatex on the old very hard gasket, put in a new set of plugs, and filled it with fresh Rotella 15W-40 and fired it up today.  Knock isn't as loud as it was but still there of course since I haven't done anything that would fix it yet.  No oil leaks though. 

Was going to check the top end next so I'll have valve cover off to check valves and can check the CCT like you suggest while it's open.  Been 3 years and 15k miles since I checked valves, geez I use to go 15-20k miles a year on my GSs.  I do remember what cam chain noise sounded like from my old Hondas that didn't have auto adjusters and haven't heard that noise on the GS.

Still not sure if I'll try to check balancer bearings thru the right side covers.

Quote from: robfriedenberger on April 03, 2014, 12:57:07 PM
Pull the rotor, my starter clutch was making that nose due to being locked up and jumping, I don't think there was any play in the rotor either


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I buttoned the left side back up today Rob and got it running again before I saw your post.  I really checked that starter clutch as best I could though.  When I first came home with the knock I shut it off and restarted it repeatedly and it fired up so fast I couldn't hear the starter turning and released every time.  Then after I had it opened up I grabbed the big gear on the back of the rotor and turned it ccw and it turned the crank and then cw and it turned free and did that repeatedly and it all seemed to be working OK.  Hope I didn't miss anything, thanks for the input.

Opened the top end today to check out the cam chain tensioner and no problem there, looks good to me.  Turned engine over with wrench on crank with plugs out a number of times even reversing it a bit from time to time and no slack in top run between cam sprockets.  Looks same as it has for the last 100k miles.   

Said after my last valve check 3 years and about 15k miles ago that it would be my last check.  With the new wider gaps on the exhaust valves they were holding settings as good as the intakes.  But with it opened up I had to check them to confirm.  All good all around, both intakes still at .003" clearance and both exhausts about .001" tighter to .004" on left and .003" on right.  They got a long way to go before they need shims again!

http://www.gs500.net/gallery/data/500/GSvalvelogs.jpg

Will button it up tomorrow and take it for a ride before deciding what to do next, might just get some ear plugs and keep on going.     It did knock less and sound quieter after I checked out the goats possibility and the starter drive and put in fresh oil and new plugs a couple days ago.

Its possible that the CCT was sitting in 1 spot but the first ride got it warmed up and shaken loose.
You think it could be the cam shaft side play ?
Cool.
Buddha.

I had the camshaft side play knock on both my 97 and 02 GSs at one time but haven't heard it for years now.  The knock I heard this past week was at a frequency similar to an engine bearing knock and the cam knock is at a much lower frequency.  The cam knock being only when hot, only at idle, and goes away when speed is picked up to a fast idle or faster part of it is similar though.  I'll take a look at current camshaft side play before I button it up.

Some interesting thoughts on GS high mileage (100k) engine wear, when I pulled the valve cover I noticed the cam lobes looked very dry and the pockets in the head where they dip in the oil were only half full of oil and I have always noted they were full previously indicating little or no valve seal leakage after sitting overnight.  When I started turning the engine over with a wrench the cam lobes immediately came up wet so enough oil for that I think.

Also I would from time to time crank the engine with the cover off to observe top end oil flow.  It was only a short time with the engine spinning free with the plugs out until the oil would spill over the front edge of the head if not watched carefully indicating ample oil flow even at cranking speeds.  With 100k miles on it now the pockets were not filling fully with a lot of cranking but I soon noticed oil was coming out the ends of the camshafts thru the worn bearing journals instead.  Probably accounts for the half full pockets more than seal leakage does.

Rod bearing knock usually starts on shut throttle, not on open throttle.
Cool.
Buddha.

So did you ever get this figured out ?

I finished with it yesterday for now Rob but won't get a chance to ride it until tomorrow, was going to post on it again after the ride.  Family Easter dinner today, daughter who took over having the family dinners when she became the grandma 11 years ago has to work next weekend and our 2 oldest great grandchildren will be up from Pittsburg this weekend.

I first checked out goats and starter drive and put in fresh oil and new plugs and the knock has only been half as loud since then.  Next had the top open to check CCT, valve clearance, and camshaft side play.  Based on piston slap I first heard last summer and quieted with 20-50 oil then I tried to check piston knock next.

On multi cylinder engines piston slap can usually be isolated by pulling off plug wires one at a time and knock will stop when knocking cylinder is not firing.  Not as definitive on a twin but still effective I think, when I pulled off #1 wire the idle dropped from 11-1200 rpm to about 500 rpm and knock was subdued, when I pulled off #2 wire the idle dropped to same 500 rpm and knock probably on firing #1 cyl was louder and pronounced.  Based on engine keeping on running on either cyl only at reduced rpm I think valves are still in good shape but knock is coming from #1 piston.

So I'll ride it and see tomorrow, I did find that knock was considerably reduced with idle speed increased to 1500 rpm.  It was gone above 2k or so when I first rode it home knocking last week  so if I never stop again I won't hear it again until it blows.   

Edit:  Forgot to cover plug condition.  Prior to last week I had previously last changed plugs at 96.8k miles and plugs came out quite black from excess oil.  Before that the plugs had always been a nice light beige or gray color and all replacements were the stock DPR8EA9 so I put in one grade hotter DPR7EA9 plugs then and they came out less black now 4k miles later.  The 2nd set of DPR7EA9 plugs I put in last week having been run in the garage off and on for a week now were beginning to blacken also with the one from #1 cyl being considerably darker than the other confirming it is that cyl that has looser piston/rings and is the knocker.

I ran a GS to the point where it used a quart of 60 wt in 300 miles. It still didn't piston slap.
Yea it got goats @ about 45k, it ate the crank trigger @ 35, it destroyed lots of things ... but not got piston slap. I almost think this bike can not get piston slap.

Cool.
Buddha.

Try using a stethoscope to figure out where the sound is coming from?

With the symptoms you describe, Jack, it sounds like you might have a cracked ring land and possibly broken rings too. That would explain the changing noise (with load) and the change of plug colour (color). It is not uncommon on old pistons. Piston slap is usually caused by excessive skirt to bore clearance and (almost) disappears when warm as the skirt expands. There is a fair chance that a big rev could see the piston crown separate from the rest of it.

Macka 

Piston slap is pretty easy to diagnose by ear isn't it... (screwdriver stethoscope method). As is valve clearances.
(I've harped on about this before), -check the starter clutch drum. If the bolts that mount it to the back of the flywheel rotor come loose like mine did it, -the sound is somewhere between a rattle (like valves) or knock (like big-ends/mains). More of a 'clanky' sound. it was hard to diagnose by ear.

Quote from: prmas on April 14, 2014, 12:23:31 AM
With the symptoms you describe, Jack, it sounds like you might have a cracked ring land and possibly broken rings too. That would explain the changing noise (with load) and the change of plug colour (color). It is not uncommon on old pistons. Piston slap is usually caused by excessive skirt to bore clearance and (almost) disappears when warm as the skirt expands. There is a fair chance that a big rev could see the piston crown separate from the rest of it.

Macka

Thanks for the input Macka.  I was thinking of an old high mileage flat head 42 Ford V8 that I had decades ago which broke a piston that way as I took what will probably be my last ride on the 02 GS yesterday.  Kept the speed and revs down and it still runs as good as new as it has for 100k miles and the knock at idle up to 2k rpm or so is constant cold or hot and it should quiet down as the engine heats up like you say if it was piston slap.  Broken rings and/or lands makes sense, the oil I filled up to the top of the dipstick flat with fresh 10-40 last week could not be reached after my short 20-30 mile ride until I screwed it down to barely reach the hot oil.   Got a couple more things to check today or tomorrow before I pronounce it dead.   

I opened the lower left covers first and checked the alternator and starter drive, all looked good in that area.  Next the top was opened to check CCT, valve lash, and camshafts side play.  All good in there too, thanks for the input, Jools.

Wouldn't a rebore to 0.5 mm over with new pistons and rings fix the issue?  I'm guessing you are saying it's dead since it's not worth the investment into a 100k mile engine.

Even if you pronounce it dead, can I request an autopsy, possibly alongside a video or some form of recording of the noise? Always good to have more info on potential issues.

My Tracfone doesn't make vids with sound.  I had the head and cyls off to repair a broken exhaust valve caused by a tight bucket back about 9 years ago and it didn't seem like a tough job then but it seems much more difficult now.  Doubt I'll pull the head again but would like to see in there myself, maybe?

I checked the oil hot twice yesterday after the ride sitting on the bike holding it vertical and stick didn't reach the oil so I checked it again screwing it down and dipstick just reached the oil.  When I checked it again today cold the oil level was down a bit from the top of the flat where it was after last weeks refill to the F letter above the full mark, not nearly as much oil lost as I thought on my short ride.  Haven't figured that one out yet.

Warmed it up again today and pulled plug wires one at a time and it still idles at reduced 6-700 rpm on either cylinder alone.  With left wire pulled the knock quiets down a bit and with the right one pulled it knocks loud and sharp, much louder than when on both cylinders at 11-1200 rpm.  Looking for a stethoscope to have a good listen to it while doing that.