Hello everyone, I have just got my 96 GS500 (26k miles on the clock) and fortunatley came across this site - great forum. :nana:
It has saved me from a (hopefully) unneccessary engine rebuild already - knocking sound when warm & at idle anyone??
Hopefully this is just the cam end float that has been mentioned on here many times, so I am now just checking the valve shims & giving a good service then ride it to see if the knocking really is just this.
Which brings me to my question:-
The valve shims are all at the top end of tolerance for clearance except the left exhaust which is at about 0.01mm. I will increase the gap on the exhaust valve, but is it ok to leave the rest?
The valves do seem really noisy to me when riding, makes a loud ticking noise. This is my first bike and my first ever time on an air cooled bike, so how loud should the valves be when riding?
They dont seem too bad when stationary and revving the engine its just when riding.
Maybe just me being too sensitive to the natural noises of the bike? :?
Air-cooled engines are noisier than water-cooled ones. I'm so used to it, and it is impossible to diagnose noises through e-mail, so I can't tell you if your's are unusual.
Knocking at idle when warm can be a bad thing. Worn bottom end bearings can do that. The best way to test that I know of, is to get the bike warm, and then in first gear with the front brake on so the bike doesn't move, rev the engine a bit so it doesn't stall, and load it up by partially releasing the clutch. The object is to get load on the engine at low rpm. It's not particularly good to slip the clutch under load like this, so don't do it any more than you have to. If the bottom end bearings have excess clearance, the knocking will get much louder. If it doesn't get worse, than it likely isn't the bottom end.
Cam end float isn't usually an issue, and I don't remember it being mentioned here. Maybe I missed it.
If the valve clearances are within the spec 0.03 mm to 0.08 mm, just leave them. I don't know how you could measure the one valve at 0.01 mm. That is 0.0004", four ten thousands of an inch! I can't imagine using a feeler guage that thin, even if you did find one.
Noise from cam end float will only be present when cold - when hot, expansion takes up the gap.
Thanks for your replies, even if you are making me paranoid about the engine again ;)
I will try loading the engine up in first tomorrow when I get it all back together again to see if the noise does occur then.
The 0.01 is a guess as the clearance is less than my smallest feeler gauge, but slightly above 0 as the bucket & shim can still be turned by hand.
I'm sure I found plenty of posts about cam end float when warm, did a search on "cam noise" I believe. Maybe it was just wishful thinking, really don't want my bike off the road for the time it will take me to do a rebuild, not to mention the cost. :cry:
Lots of posts about cam chain noise I believe, but not cam end float.
I've been building up various GS engines, and I've had a problem even finding a spec for the cam end float. Some cams have shims to reduce the end float, some don't. The end float doesn't seem to make any difference to engine noise I can detect.
I remember a few threads where a sound like Mumu's was discussed.
For example, in Tired cam chain tensioner? (http://www.gstwins.com/forum/viewtopic.php?t=1828), gsJack talks about "camshaft sideplay" and refers to it as causing this "long-discussed noise".
I found that at least one of the camshafts on my '96 does have some sideplay, and I have stopped worrying about the "soft clunk" it makes at idle.
Well. there you go! I missed that thread entirely.
I disagree with the idea that it is cam end play making a noise at idle, or any other revs. There isn't anything to put a side load on the cam to make it go "clunk", softly or otherwise. The cam lobe centers are lined up with the lifters. The end play in the cams is quite small - they seem to shim it to keep it under 0.2 mm or so. I can't imagine what would shift it sideways firmly enough to make a noise audible over all the other racket at idle.
More likely cam chain slap, as the load reverses when the lobe kicks over center?
I made a mistake above. To tighten the cam chain manually, you would turn the screw counterclockwise.
Yay, I wasnt imagining it :lol:
I had another quick look through to be sure, and it seems to have been GSJack who mentioned it being end float. He was maybe talking about a different sound though, it is a bit difficult to know by text :?
Guess I will have to see whether KevinC's suggestion of loading the egnie at low revs shows anything up tomorrow.
End float dont make much noise when cold or hot...Cam chain OTOH when cold is likely to be noisy till it get oil on it...and that makes it quieter...
Cool.
Srinath.
Welcome to the site Mumu! Hope the engine noise is the regular ol' noisy air cooled engine we all ride!
Make sure to check out the valuable links and info found on the gstwin home page and on my page as well...
Let us know how it goes tomorrow with the noise....
Thanks for the input.
I got round to re-shimming the left exhaust valve today and found that it was in fact riding the cam the whole time. Had to go down from a 2.55 (it was slightly worn though - just over 2.50) to a 2.35 to get the correct clearance - I did ensure that the oil had thouroughly dissipated from under the shims before re-measuring. Possibly this valve was no longer closing fully when warmed and further adding to the noises??
I guess if that is the case then the valve seat / stem wont be in too good shape, but I will leave that for now.
I've not got the bike completely back together (too many things getting in the way of valuable bike time :( ) but I did run the engine up and tried loading it at low revs as suggested, and it sounded fine :)
So fingers crossed it will be ok when I get it back on the road next week.
You did not drop 4 shim sizes in 1 shot...you have oil float...get it back together and ride it a little...if not too noisy and open up and remeasure...There have been people here that have had to ride 40K (including myself but mine gets thicker not thinner) miles for that kind of change...
And easy to rotate by fingers is a sign you have clearance...and its not being held open during the power cycle.
Cool.
Srinath.