Another GS another noise

[John Kat]

I'm so happy I got rid of the "loose marble" noise in my GS 1000 EC that I have now decided to tackle another kind of noise in my GS 1000 XP.
The engine comes from a GS 1000 ET with CV carbs fitted with pods.
.
The noise definitely comes from the valves but strangely enough only when I ride the bike???
Needless to say the clearances are within spec, the valves are new and so are the valve guides.
I suspect it comes from the camshaft bearings.
The reason is that when I bought the bike, one post of one of the "half bearings" was broken.
I managed to find another half bearing that carried the same identification number but the noise did not disappear.
Else, could it be that the "valve" noise propagates better through the pods than through the normal airbox I have on my other bikes?
Any advice on what to do next (except throwing the head in the dustbin)?

[hampshirehog]

What caused the cam cap to break - did you find out? Have you replaced the cam(s) as well?

And what sort of noise is it - can you describe it?

[John Kat]

I suppose the previous owner did not follow the procedure to remove the camshafts ( i.e. holding the camshaft in place until the half bearings are removed) and broke one the posts in doing so?
The best description of the noise would be like there is too much clearance at the valves...
By the way, I checked a manual I have and it states that the clearance at the bearings of the camshaft ought to be between .025 and .053 mm for the GS 1000 EC/EN/SN while it should be between .037 and .065 mm for the GS 1000 ET/ST/G.
Kind of strange no?

[hampshirehog]

Might be worth plastigauging the clearances of the cam - especially with the new cam cap. As the caps are drilled out at the same time as the head there will be a mismatch with the new cap - just a case of how much. Rather than run the plastigauge across the cap, run it around the circumference (hold in place with a dab of grease) and you'll be able to check for uneven.

Tip - spray the plastigauge with silicon spray first and it won't stick to badly.

[Nessism]

Cam caps are line bored to the head and ideally should not be swapped. People have reported success with swapping caps that had gotten damaged, but checking clearance is a very good idea to make sure the new cap is a good match for the engine.

Hog has some good suggestions. I'd follow them and report back with your findings.

[Guy]

When you say the noise only happens when you ride the bike, d'you mean when there's a load on it, or when you open the throttle?? You'll hear more intake noise through the pods with the throttle open, but not mechanical noise. It could be running lean and pinking too, which could be mistaken for valve noise.

Btw, swapping cam caps almost always results in some top end noise because of imperfect alignment of the unmatched caps. It might be a good idea to check the cam(s) for run out too, especially if someone's been heavy handed and breaking caps in the past.

[John Kat]

Btw, swapping cam caps almost always results in some top end noise because of imperfect alignment of the unmatched caps. It might be a good idea to check the cam(s) for run out too, especially if someone's been heavy handed and breaking caps in the past.

You are right, so is Nessism, it's not a good idea to swap cam caps but when one is broken there is not much choice...
I will measure the clearances as soon as I get some time.
I had not thought about the run out issue...
Thanks!

[John Kat]

I got the plastigage today and promptly started measuring the camshaft bearing clearances.
First cap D ( right intake) as this is the one that I exchanged.
Here's the picture:

The clearances range from .025 to .051 in line with Suzuki's spec.
While I was at it I decided to measure one of the exhaust bearings.
I chose to measure cap A ( exhaust left)

Again within spec!
Tomorrow, I'll check the valve clearance one more time and will start looking elsewhere for the noise source

[John Kat]

Before closing the camshaft cover, I checked the valve clearance.
Guess what? One of the exhaust valves was at .20 mm and two others were at .10mm.
On the inlet side they were all OK at .05mm except one that was almost at zero clearance
I wonder how this is possible as I checked the valves less than 1000 km ago?
FYI, I had a complete valve job done a year ago and some of the valves had to be shortened as the seats had sunk further down the head.
I believe the valve stems are hardened at the factory and maybe that shortening them might have created this problem?

[John Kat]

I set all the valves at .05 mm and the valve noise has decreased but not quite to the same level as my other GS 1000's...
The cause might be that as my final ratio is shorter than the original one, the engine revs higher when riding at the same speed???
By the way the noise (clickety clack type) is stronger around 4500 rpm and then reduces higher up in the RPM range.
At idle no significant valve noise at all???
No pinging whatsoever even at WOT.
The mystery remains!

[hampshirehog]

2 other thoughts at random.

I guess you checked all the shims are Suzuki and that a Kawasaki one hasn't sneaked in there when you weren't looking.

The other one is a bit off the wall but are you sure the noise isn't from the carbs? I was thinking worn slides or something bouncing around on top of the diaphragm.

[John Kat]

What's the difference between a Kawasaki and a Suzuki shim?
I noticed that the new Suzuki shims I had to buy were a very tight fit in the bucket.
The only(?) difference with my other GSs is the fact that this model has CV carbs with pods.
The others have the 26 mm or 30 mm Mikuni carbs with the original air filter.
Thanks for the help!

[hampshirehog]

The Suzuki shims are 29.5mm in diameter and the Kawasaki ones are 29mm. Easy to miss as the sizes are so close but if you have some shipbuilders shims in there they'll rattle (and possibly fall out, though I haven't seen that).

Suzuki stamp the shim size in the centre of the shim like this (sorry, small photo): http://images.cmsnl.com/img/products...40-01_d4bc.jpg

whereas Kawasaki stamp the numbers offset like this:

http://www.vintagecyclepart.com/product_images/o/989/DSC07960(1)_Shim__43173_zoom.JPG

Plus the oversize Suzuki shims are X shims (eg 2.75X) whereas Kawasaki use an A to denote oversize.

[John Kat]

That's good to know specially when the bike has been in numerous hands before
The shims I have are of three types as you can see on the picture.
To the left a brand new shim from Suzuki and on the right two other type shims I have used.
Interestingly enough some have a coma before the decimal numbers and some a dot
As I said previously the new shims are definitely a tighter fit than the old ones although when I measure them there is maybe only a 1/10 th of a mm difference in diameter?
All are above 29 mm but none at 29.5 mm...

[Nessism]

It's hard to judge a noise over the internet but GS engines are not overly quiet even on their best day. My guess is your engine is normal.

There are threads about "cam walk" causing noise on shim and bucket GS engines. I don't know what this particular noise sounds like but maybe that's part of the issue with your engine. Not sure, but you might want to dig around in the archives to gain more knowledge. Basscliff is hosting a tutorial on how to eliminate the walk, but it's quite involved and requires machining the head.

Good luck