Exhaust Valves getting looser over time

[user11235813]

While the inlet valves have remained .06mm the whole time, the exhaust clearance has gone from both .05mm at 27k/kms to both .06mm at 35k/kms to .08mm and .09mm at 45k/kms

Is this normal? should I expect them to continue this trend. Or are there other variable that could reverse the trend?

[1018cc]

That is weird. When they wear they get too tight. They are wearing in completely the incorrect direction - at the rate you are going you'll have to find some thicker shims next time!

I've got nothing constructive for you sorry other than something seems up.

[user11235813]

@1018, OK that's something, I'd only ever heard of people discovering their clearance was too tight but I never knew for sure which way they are supposed to wear. All I can add is that the clearance was checked after the head was retorqued, not sure if that is relevant or not, previous times it's possible that they were checked before a retorque.

[Big Rich]

Have you done a compression test? I'm wondering if maybe you have carbon build up around the valve seats.

[mr72]

Has to be carbon build up. Better do something about it because it cam potentially lead to burnt or bent valves.

[Joolstacho]

are the camshaft cap bolts tensioned down properly?

[user11235813]

Bugger, I was happy that they've moved into a better spec, now I'm sad again :¬(

Will a cheap $20 tester like this be OK...
https://www.ebay.com.au/itm/AU-SHIP-Petrol-Engine-Compression-Tester-Kit-Tool-Set-For-Automotives-Motorcycle/262525463116

@Joolstacho, have not checked yet.

@anyone, if this is just a bit of carbon build up can this be attended to without removing the valves by running some sort of product through the engine? Also how big a job would it be to clean the valves. How much disassembly would it involve.

Also let's say hypothetically I get a good compression, what would that mean with regard to the next step to take. I will note that the bike runs well and does not feel that it's losing power anywhere.

[Big Rich]

are the camshaft cap bolts tensioned down properly?

Good idea Jools- I didn't even think of that. User, if you check the cam cap bolts, do NOT over tighten them! Don't want to add another problem......

I've heard of so many different ways to clean carbon build up, but have never tried any of them (if you Google them, they seem like sketchy procedures......but people claim each one works). If you want to do it properly, it might be a good idea to take the head to a small engine repair shop. Removing and cleaning the valves isn't exactly a hard job, but it does take some special tools and it can be devastating if you do it wrong (especially reassembly).

[user11235813]

OK I can't find 'camshaft cap bolts' listed in the service manual. Are these them?

[Big Rich]

Yep.

[user11235813]

OK, right well I've ordered a cheap compression tester and I'll get it checked at the garage as well to check the calibration. In the meantime while I'm waiting for my tank to empty so I can check the journal cap (which looks to only be 10Nm anyway) I have a question.

This has always had top quality 100% 91 octane which I believe is equivalent to (87 in the states) and it is rarely fanged, and only 45k/kms what would cause it to accumulate carbon build up on the valves, (assuming that a retorque of the cap doesn't alter anything)

Also if this is a carbon build up and there is some consequent leakage what would you expect the psi to read assuming that the piston rings and any other stuff where pressure can leak are not leaking? hope that makes sense. Alternatively assuming that there is not leakage anywhere what reading would indicate that? Over 160?

[The Buddha]

On my 50K bike everything used to get loose with wear. That's an indication cams, shims etc are wearing more than the valve and seat. IMHO - good thing. Easier parts to get at.
Cool.
Buddha.

[mr72]

That's an indication cams, shims etc are wearing more than the valve and seat.

I would think that's pretty much impossible considering those are hardened steel and the valve seat is bronze.

[gsJack]

I found that exhaust valves set at the minimum .001" of the Suzuki .001-.003" spec required constant shim changes and the one on my 97 GS (bought new) was down to a minimum 215 shim with no where to go at 70k miles.  While I was pondering what to do next I was rear ended and the bike totaled and replaced with my 02 GS.

Early on with the 02 GS I began setting exhaust valves at a wider .003-.005" spec and they settled down and required little attention after that.  Minimum shim at 100k miles was a 245 with plenty of adjustment left.

Both the 97 and 02 GSs had the same intake valve shims in them that they came from the factory with, no shim changes.  My valve check log:

https://i.imgur.com/SksMPhb.jpg

[gsJack]

That's an indication cams, shims etc are wearing more than the valve and seat.

I would think that's pretty much impossible considering those are hardened steel and the valve seat is bronze.

I've measured valve shims with tens of thousands of miles on them at both centers and edges with a quality micrometer and never detected any wear in them.

[The Buddha]

That's an indication cams, shims etc are wearing more than the valve and seat.

I would think that's pretty much impossible considering those are hardened steel and the valve seat is bronze.

Cams are not hardened. They're treated with something - not exactly making them hard. Something that makes them retain oil maybe ?
You understand that there is no back and forth movement on the seat/valve contact face right. The cam drags across the shim, with the oil film protecting them. Valve/seat doesn;t have oil, it has a thin layer of carbon but there is no sliding friction.
BTW mine had a crows foot type scratch on one that I watched for 50k miles and it did get slowly fainter over time, but never went away.
I have measured shims and have found them thinner than the marked number, but not had them wear in the time I have used them.
I've seen weird wear patterns on them to start with, no wear occurring in my use.
I dunno, I had that bike with pretty rough commute type use for much of its life, it used oil prolifically and never skipped in spite of any of these problems.
Cool.
Buddha.

[Joolstacho]

OK I can't find 'camshaft cap bolts' listed in the service manual. Are these them?

BUT! (I should have mentioned), -take care not to overtighten these bolts as they can easily strip the threads in the head if they're over-torqued.

[user11235813]

I will report back on friday, when my $20 compression tester will be delivered, I'll also be getting a $10 check at the local bike shop to check the calibration on the cheap tester.

Talking to the bike shop the offered the suggestion that the difference could be accounted for by the weather. Earlier tests were done in winter. However there was no change to inlet valves and winter in Brisbane would be close to summer in some places.

@Joolstacho, yeah I've already double checked it to be 10Nm and I have a decent inch/lbs torque wrench. However seeing as the torque is so low, if these bolts were loose wouldn't that cause some very dramatic problems? Also Suzuki never mention even checking them during a head retorque. But I will check anyway.

BB Friday with the compression result.

BUT if there was enough carbon build up to give me another .002 - .003mm of clearance, would you expect to see that reflected in the compression numbers?

[Big Rich]

If carbon is building up around the valve seats, your exhaust valves would be slightly open all the time. So yes, your compression would be lower than it should be.

[user11235813]

@Big Rich

Cool, can't wait till Friday. Will report back.