Hey everyone,
I have a 2005 GS 500E that has an annoying rattle problem. It sounds ominously like a cam chain tensioner issue, but it also coughs and splutters every now and again. Almost like a sneezing sound, like a pop and then it drops rpm and then recovers. I'm thinking this might be timing related or valve blow back?

Here are a couple videos. The first one has the rattle only and in the second one you can hear the popping sound around the 40 second mark.






So I ripped her open today to do a diagnostic and take some symptoms down so here they are:

1 -
Once I had the air filter box off I started her up and I noticed that the right carburettor slid seemed to "flutter" up and down, but not the left one. I have read that it is common to have slide flutter but I'm still not sure why it happened on the right side and not the left?


Next I took off the rocker cover and checked a few things.

2- I changed the cam chain tensioner (in the hope that it would fix my problem but it didnt) -the cam chain is still tight.

3 - I measured the length of the chain for stretch. 21 pins = 156.4 mm (according to this sites 'how to' page, If you measure 20 links (21 pins). They should measure no more than 157.8mm". So it seems my chain is not stretched).

4 - I measured how much vertical travel the chain had in the centre of the block. 10mm max when pressing and pulling it.

5- I measured how much sideways play the cam shafts had when the cam lobes were not engaged. 1mm each which seems reasonable but it DID make a klacking noise when I did it. I'm assuming that this is normal however as there is a spring washer on the right side of both cams to account for sideways play in the cams.

6 - I checked the valve clearances. The measurements were as follows;
IN right - 0.07mm
IN left 0.05mm
EX right 0.06mm on the left side of the cam lobe and 0.05mm on the right side of the lobe.
EX left 0.10mm

I measured the EX side at one full crank turn from where i measured the others. Is that right?
Also, I assume that something will need to be done about the EX left shim plate, but what about the others? Do they need to all be uniform, or are they okay as long as they're no more than 0.07mm gap?

Sooooooooooo, anyone got any ideas?

Thanks in advance y'all

-Tom

Tommet, I think that the noise may be the balance shaft bearings. There are threads here for that symptom.

As for the backfiring/popping at around 2000 rpm, my K9 has always done it from new, particularly when not yet warmed up fully. I suspect that it is due to the very lean mixture and retarded ignition timing. Mine will also occassionally backfire into the air cleaner if I open the throttle very quickly from very low revs eg: blipping the throttle on a low rev down shift when slowing down. It is nothing to worry about but rejetting and an ignition advance would probably eliminate it if not already done. GSJack will probably be able to confirm or reject my suspicion.

Macka

Cheers for the help Macka, I'll look up balance shaft bearings now.
So with the backfiring through the intake, you don't think it would have something to do with that left exhaust valve shim that is at 0.10 mm?
-Tom

Tommett, I take it that you meant that the exhaust valve clearance is 0.1mm, not that the shim is 0.1mm? At 0.1mm the exhaust valve clearance is fine and cannot cause a backfire. A backfire is usually caused by a lean mixture or retarded ignition timing. The standard GS comes from the factory with BOTH built in to achieve low exhaust emissions. I have not felt the need to alter mine as it is not really an issue that affects normal riding/use. My bike is perfectly happy 99.99% of the time. If yours has more frequent problems you may need to do something about it but I can go several weeks between backfires so it does not bother me. It does not affect my riding at all. It never runs roughly or stalls unless it is my fault (wrong gear-LOL).

Cheers,
Macka 

Yeah I'm talking about the clearance on the left exhaust is 0.1 mm .I thought the max acceptable was 0.08mm?

-T

Your valve clearances are OK.  Many of us here run clearances up to .13 mm on the exhaust side to keep the valves cooler.  Unfortunately, that probably means you have an issue in the bottom end.  Did your bike run low on oil at some point?   If you drop the oil sump, you might see metal shavings (bad news ).  You can also get a look at the outside of the counter-balance bearing by taking off the side engine cover.

Ouch, No bueno, has it always idled that low it did the idle drop when it started making that noise? Have you tried a long screw driver or mechanics stethescope to detirmine where the sound is coming from?

Quote from: bombsquad83 on June 17, 2013, 07:06:08 AM
Unfortunately, that probably means you have an issue in the bottom end.  Did your bike run low on oil at some point?   If you drop the oil sump, you might see metal shavings (bad news ).  You can also get a look at the outside of the counter-balance bearing by taking off the side engine cover.

Nyaaawww, ill pull the side cover off tonight and have a look at that bearing. It does sound a lot like the "junior dies and lives again" thread http://gstwins.com/gsboard/index.php?topic=60331.0

Not sure about the history of the bike in regards to running low on oil or when the idle dropped. I bought it with the noise about a month back ( I was convinced it was a simple cam chain tensioner problem, more fool me).

I'll playw ith theidle adjuster next time I've got her together again.


-T

Update:

So it's not the balance shaft bearings. Theyre solid. As are the crank bearings. Nothing seems to have any "up down left right" play at all. Everything pushes "in and out" a little ( 0.2mm ) along thier prospecitve shafts, but nothing that should casue such a noise.
There is a bit of play on the large gear behind the alternator. Is that normal? I feel like i shoul dbe looking for play that moves up, down, left and right as oposed to in and out???

Here's a video



So that means, its not the balance shaft bearings, the cam chain or tensioner and no other bearings that i could get my hands upon?!?!? Is that alternator gear a problem??

Anyone got any ideas?
 

-Tom

The gear behind the magnet rotor is the starter gear. It has a one way clutch. There will be a little play there.
While you're open, examine the magnets for any damage. Look at the stator, too, for any damage. Close tolerances between stator and magnets.

Hmm, so as much play as in that video? The starter gear can touch the side of the crank case and make a bit of clunking noise...
The internals of the alternator seem okay. There are no wear marks. (I wish there were, I'm going crazy here not knowing what this noise is  )

-Tom

I don't recall a starter gear hitting the inside of the case. It is not tight because it floats on the bearing shaft and has a one way clutch locking it to the rotor when you are starting the bike.

Where and how can it hit the inside of the case?

I suppose it could be possible for the inside bearing of the starter gear to be worn causing it to flop around.

Quote from: Tommet on June 20, 2013, 03:32:51 PMThe starter gear can touch the side of the crank case and make a bit of clunking noise...

A new one on me too........I guess if its doing that you really have got problems 

Agree with suggestion the idle speed seems low, the bike is obviously struggling to tick over. I would concentrate on trying to get it to run a bit better first.

What are the plugs saying?....any indications that its running rich?

Try cleaning out the carbs and sync`ing them and have a good look at the CV rubbers at the same time.

Plugs seem okay. Just thinking about it, it does drink a lot of oil. About a litre in two months.

What are cv rubbers?

-T

http://jbmindustries.com/Yamaha650.html

Hmmmmm okay.
I took the oil pan out, no metal shavings. I cant find ANY play in any of the shafts, crank banacer etc.
The play I found in the starter motor gear was removed as soon as i put the starter motor reducer gear in.

Im totally lost...

What about the cam chain guides? If one of them were scored or broken even, could they make such a noise if the cam chain wasnt running as it was supposed to? How could i tell?

-a very confused and exasperated Tom 

Your bike is showing all the signs of unbalanced carbs. Vibration, rough idle, hesitation, poor throttle response......google it 

Get them cleaned out, checked and dialled in and it will run better, you might even find the noise disappears.....lets face it you have checked just about everything else. 

Quote from: Tommet on June 21, 2013, 08:31:56 AM
Hmmmmm okay.
I took the oil pan out, no metal shavings. I cant find ANY play in any of the shafts, crank banacer etc.
The play I found in the starter motor gear was removed as soon as i put the starter motor reducer gear in.

Im totally lost...

What about the cam chain guides? If one of them were scored or broken even, could they make such a noise if the cam chain wasnt running as it was supposed to? How could i tell?

-a very confused and exasperated Tom 

This is all good news!  Try getting the carbs cleaned, tuned and synced and hopefully that will solve the issue.

Quote from: Tommet on June 21, 2013, 08:31:56 AM

What about the cam chain guides? If one of them were scored or broken even, could they make such a noise if the cam chain wasnt running as it was supposed to? How could i tell?

-a very confused and exasperated Tom 

You can remove the valve cover. In there are the two main cam chain guides.
First check if the cam chain is tight.
You can examine the chain guides by looking down in there. To really get at them you may have to remove the head.

However, if you were to remove one cam and roll it out of the way (keep tight on the chain and do not drop a tooth - then you don't have to re-check the timing **) you can clearly see one guide. Then roll that cam back and remove the other one to see the other guide.

If they look good and the chain was tight, I think you are OK in that area. Only one time have I heard of a cam chain guide breaking.

** If you remove one cam and keep it on the chain, when you put it back it will still be the correct timing.