My recent thread about the knock in my 100k mile 02 engine finally resulted in finding the knock was from the right cylinder after checking every other possibility.  First thing I checked was the compression with the finger over the hole, crank, and pop method and pronounced the compression good in both cylinders and went on from there.  But how good really was it on a 100k mile air cooled engine?

Having lost the compression gage I had for years I finally went and got a new one today, better a decade or two late than never.   

Results of todays compression check:

                  #1 cyl             #2 cyl
Cold             135 psi          135 psi
Hot              140 psi          140 psi                           
Oil added
to cylinder    155 psi          160 psi           
                   170 psi          190 psi
                   200 psi          190 psi

Suzuki Spec:



Surprising how good it still was, with about 140 psi in both cylinders it was at the bottom of standard range but well above the minimum limit of 114 psi.  Most surprising was the lack of difference between the two cylinders, they were the same, a 28 psi difference is allowed.  Good oil and plenty of it pays off in the long run, 15W-40  Rotella T in this case.

When the oil added to "bad" cyl #2 increased it above #1, I put a little more oil in #1 and checked again and back and forth until they topped out at about 200 and 190 psi.  Rings are well worn but it shows the value of using the new wide exhaust valve spec.  Valves are surprisingly good at 100k miles.

Expect I'll just run it for the summer for the little I ride now and maybe pull the head in the fall if it doesn't blow before then.   

Ref:  http://gstwins.com/gsboard/index.php?topic=66928.0
                   

Damn, put some new faith in my bike for me haha 

What is this exhaust valve spec you speak of?

Your compression is actually very good. Adding oil will increase the compression cos you're taking away volume. That oil test is for compression in the 50's and 60's.
My 89 when it had like 45k measured much lower than that.
Also that doesn't explain the knocking either.

Cool.
Buddha.

jboogie13, the tighter of the 2 exhaust valves on my 97 GS running at the minimum Suzuki spec most of the time required constant shim changes and was down to a min 215 shim by 80k miles.  When the tighter one on my 02 GS started the same pattern at about 30k miles I increased the exhaust valve clearances to .003-.005" (.08-.13mm) and they stabilized after that requiring little more change than the intakes did.  Min shim in the 02 at 100k miles is a 245.  Suzuki's tight tolerances did not provide enough cooling seat time for exhaust valves.

http://img.photobucket.com/albums/v443/jcp8832/GSvalvelogs_zps9ef7236a.jpg

No the good compression doesn't explain the knock and possibly has nothing to do with it Buddha, but I find it of great interest to myself and probably others seeking long mileage from their GSs.  So that oil test is for compression in the 50's and 60's?  Well I'm a man of the 30's!  Adding oil increases the compression by sealing the worn rings.  I've got a new theory on that knock after hearing new sounds.   

What gsJack is talking about is referred to as cylinder wash, the volume is slightly altered but usually only by 10-20cc.

Every modern tech that has needed to do a compression test will use a bit of oil to rule out cylinder integrity issues. From the knock I'm thinking some thing with the connecting rod. I guess the motor is on borrowed time now so if it dose blow it will be ok?

I've see some small blocks blow connecting rods out of the bottom of the sump, knocking isn't some thing to play with.

Quote from: gsJack on April 30, 2014, 06:49:31 PM
No the good compression doesn't explain the knock and possibly has nothing to do with it Buddha, but I find it of great interest to myself and probably others seeking long mileage from their GSs.  So that oil test is for compression in the 50's and 60's?  Well I'm a man of the 30's!  Adding oil increases the compression by sealing the worn rings.  I've got a new theory on that knock after hearing new sounds. 

Yea oil will seal it @ the rings. But your cold compression is very very good. Your oil seal isn't the factor in making its compression go up. Its the volume you have taken up with oil. My guess ... obviously there is a bit of blow past the rings without oil, and you have cut that down with oil.
But a motor compression in the 50's due to bad rings will get to over 150 with oil for a few mins.
That is telling you have bad rings. Your rings are fine IMHO.

Toss in a head ... I had a couple I did for some locals ... I still have contacts in that line of work, I can likely get it done cheap, and I'm talking $40-50 for a 3 angle ... only the fabricator died, and the laser shop sold to a mega corp, and the powdercoating guy got his wife and mother in law pricing stuff. So a wheel done in black now costs $150 and will get me an itemized bill accounting for every grain of blasting powder used up etc etc when it used to be $10-20.

Your cyl likely is like new. 1450 is plenty good. My 50k miler made 110 or less in both when cold. Didn't prevent it from running like the dickens though.

Cool.
Buddha.

Quote from: robfriedenberger on May 02, 2014, 03:20:36 AM
............I guess the motor is on borrowed time now so if it dose blow it will be ok?

I've see some small blocks blow connecting rods out of the bottom of the sump, knocking isn't some thing to play with.

That's about where we're at Rob, motor, bike, and rider are on borrowed time.      I was hoping to ride this bike a little longer this summer and maybe next, don't consider it a big loss if I had to carry it to the scrapyard now.  I've more than got my money's worth out of it.  We're planning on moving further out in the burbs later this summer and don't need a bike laying around in parts in my present garage, timing has been very inconvenient on this problem.  I've seen con rods sticking out the side of small blocks, the last was on one of son JP's cars.

Quote from: The Buddha on May 02, 2014, 04:46:41 AM
.....................Your cyl likely is like new. 145 is plenty good. My 50k miler made 110 or less in both when cold. Didn't prevent it from running like the dickens though.

Cool.
Buddha.

That's what's most baffling about this Buddha, everything I've checked under the left, top, and right covers has looked like new on this well maintained 100k mile engine.  Can't really disagree with anything you're saying here.

Glad I checked out the compression thoroughly and feel it probably rules out a problem with the pistons and rings.  It's not a con rod big end bearing I hear, completely wrong for that.  A knocking wrist pin is still a possibility I guess. 

I've been hearing a new rattle within the idle to 2-3k rpm range that it knocks sounding like there's a loose marble in there somewhere when I blip it.  Way back 80k miles ago when I pulled the head to replace the broken exhaust valve I found about half the tip of the protruding valve guide had broke off and disappeared.  I elected to leave it as is and it's been good as new since but I'm wondering if the other half has broken off now and is rattling around in there, could it be making the loud positive knock I hear.  Probably reaching too far on that one.   

You could see that valve guide in the exhaust port ? or feel around for it after taking the headers off ?
Cool.
Buddha.

Never used my 97 GS in the winter for the 80k miles I put on it nor did JP for the 30-40k miles he added so the exhaust from it is in much better shape than the rusty patched up one on my 02 that's splashed thru the salt water for the past 10 winters.  Got 97 exhaust back when JP parted out the 97 and have it in the garage avoiding taking on that rusty mess on the 02 to change it.  Guess it's time to give it a try now so I can have a look in there, valves and guides can be seen thru the open ports.  I'll take it easy soaking with liquid wrench and wire brushing to get it cleaned up and go easy with the wrench.  If a little impact won't break it loose I have a propane torch I can use on it in my non electric old garage. 

Quote from: gsJack on April 22, 2014, 12:41:07 PM.....................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..............

Quote from: gsJack on April 30, 2014, 04:34:56 PM
My recent thread about the knock in my 100k mile 02 engine finally resulted in finding the knock was from the right cylinder after checking every other possibility......................

Well that was a week or two ago and this is now.     Was searching around last night and found a post with video from member Mach about an engine noise he had that sounded more like my knock/rattle than any I've heard so far and it was at idle both hot and cold going away at higher rpm like mine does.  Turned out Mach's noise was from a loose starter clutch, he found 2 of the 3 bolts holding it to the back of the rotor were actually broke off. 

Checked my bike again today and could not hear that knock from the right cylinder that I heard before and both cylinders had the same equal 140 psi compression as before.  Probed around again with the stethoscope and loudest noise I heard that sounded like my knock/rattle was coming from the left rotor cover.  I had checked in there before and the rotor was tight on the crankshaft with all magnets tight in place looking good and starter clutch was functioning OK so I closed it up and went on to check other things. 

So I guess I'll go back now and actually pull the rotor from the crank to check if the starter clutch is tight to the rotor.  Have only put another 20-30 miles on it riding around easy close to home since I first heard the noise.

I'm pulling for you! I'm hoping there's still more life in the old gal... I've got a vested interest in this as my '07 is pushing 83K... and I want to hang on to her as long as I can!

Gsjack is both our tire guru knowing all things tread, and the high mileage king

Pulled the left cover off again yesterday and could see the starter clutch was loose now.  First time I checked in there last month it all looked good.  I had only ridden it a few miles home after the knock/rattle started.  Rode it around 20-30 miles close to home since then and ran it quite a bit in the garage and it was quite loose now.  Had to dig out a 18" breaker bar and go back this morning to pull the 12mm bolt that holds the rotor onto the crank.  Then wasted the rest of the day going all over town to find the 14mmx1.5x45mm bolt needed to pull the rotor off, made the 36mm spacer out of another bolt.  Hopefully I'll get the rotor off tomorrow and if all parts are good get it back together and on too.  Let the thread lock dry for 24 hours and maybe put the cover on and have it running again on Friday ready for another 100k miles.  Maybe.   

gsJack, I really hope thats it!

Question.....why didn't you use the swing arm bolt? Just wondering thats all, it worked good for me maybe I got lucky?

Hi GSjack see my post on when my rotor was loose, I suggest using the locktite 660 and sanding the tapers to make sure that you don't have to do the job twice like I did.


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Here is the link- http://www.gstwins.com/gsboard/index.php?topic=67052


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Quote from: adidasguy on October 28, 2012, 10:53:10 AM
..................NOTHING ON THE TAPERED SHAFT! Clean and spotless - no grease (though I lightly scored it with some 800 grit going in and out). Use BLUE threadlock on the bolt. Do not use red and do NOT put any on the shaft!.....................

bmf, is the blue threadlock the same as the locktite 660 you refer to?  Patrick lightly scored the taper with fine sandpaper same as you did and I recall quite a bit of contention between him and sledge on this issue in another thread, sledge insisted lapping was the way to go.  I blocked the rear wheel with a piece of wood across the swingarm and did have some clutch slippage but finally got the rotor bolt loose.  Thanks for the link.

Rob, did you sand, lap, or neither?  Use any locktite on the taper?  I've done my own maintenance and repair work on my bikes for 30 years and 400k miles and never put locktite on anything and never had anything come loose either but I was planning to use it on the rotor bolt and the 3 holding the clutch to the rotor in this case.  Thought it would be easier to run over to the hardware and get a bolt yesterday instead of pulling the swingarm bolt but ended up going on to the next hardware and the next, and the next............   

No impact wrench here and no electricity in the garage either where I keep the bike across the street behind another building, would have made removing the rotor bolt a lot easier.  I still have a set of 1/2 drive 6 point Snapon inch size impact sockets though and one fit the rotor bolt nicely when using the breaker bar.   

Time to go and try pulling the rotor, it's another hot, humid, rainy day so I'll go get some threadlock and bolts if necessary after I see what's behind the rotor.  Tomorrow's forcast is for sunny and high in the 50's so that's soon enough to finish up.

By the way, took a pic inside the rotor yesterday and it looks like all 3 clutch retaining bolts backed out about the same amount and not too far yet.  Would probably have been a mess if I had tried using the bike this summer and waiting until fall to fix:


Loosing a little epoxy from the side of one magnet, no goats allowed here.     Anyway it was all worthwhile pulling the covers on both sides as you can see there was a lot of oil leaking out and collecting on the bottom of the engine, no leaks now since I put them back on.

I did lap my the tapper, and used locktite I don't remember what type though.

When I attempted to find a bolt of that thread pitch around Pittsburgh, you would of thorough that I was looking for be holy grail. The blank stares I got and the suggestions of using an imperial thread was endless.

So far I if got 2 k on my repair and it's seams to be holding good. Next oil change I'll open it up to inspect it but I really doubt I'll see any thing out if the ordinary. My bolts were loose but it seamed that because my starter clutch locked up it prevented things from going south any further.   


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