Valves...please rest my mind

[taosports]

Did my first valve adjustment on my 04 BMW R1150R with 18,000 miles. (Note I'm just a newbie here - never have done a valve adjustment in my life)

All went well after about 2 hours of fiddling with the adjustments. Warmed up the bike, adjusted the TB's and went for a spin. First impression was "Wow, this bike is running smooth" and it was/is but them comes the "what if's". Those gremlins lurking in the back of my mind just to bug me. What if I screwed up? What if they're too tight, too loose, not even. Have I lost some power here? Are the mirrors vibrating more than before? Do the pegs and grips buzz more?

Again the bike is running smooth and sounds great at idle and I really don't think I've lost any power or gained any abnormal vibrations.

So a few questions for you experts.

Do valves usually tighten when it comes time for adjustment? Noticed most of mine were very tight.

Are too loose valves better than too tight?

What are the symptoms of the above?

Thanks guys - your wisdom and help is much appreciated!

[Dallara]

Ah, yes... Valves and their adjustment.

Don't fret too much, Taosports. There has never been a professional nor amatuer mechanic that hasn't felt those same knawing feelings of the dreaded second guess. I set valves for years in shops as a line mechanic and I don't think there was a week that went by I didn't have an engine buttoned up and warming on the choke that a thought didn't cross my mind "Did I get all the valves, or did I miss one when I got that phone call?"... Or "Did I get all the lock-nuts cinched down to torque specs?", etc.

It's human nature. One might have all the confidence in the world in one's ability, but with that always goes that nagging little voice in the back of one's mind that says "We're all human. We all make mistakes." Your only possibility of avoiding it is to always double check every step of the procedure while you're doing it, and then check it all again just before you button everything up.

But chances are if you are this analytical and introspective about whether you did it all *just right*, or not, then you probably did everything as well or better than anyone else could have.

Now, to answer some of your questions...

"Do valves usually tighten when it comes time for adjustment"?

Yes... And no... The newer an engine is the more likely the valves will tighten between adjustments. Why? For a myriad of reasons, but primarily because the valves initially *hammer* the valve seats further into the head as the engine gets some time on it. Since that means the valve is moving closer to the rocker arm the clearances are tightening up. The biggest danger with this is that the valve will tighten up so much that it finally runs out of clearance and actually hangs open slightly... Power falls, but worse, combustion gases and temperature starts burning the seats, and then the valve will never seal correctly until a complete valve job is done (re-cutting and lapping the seats and valves, and you may even need to replce the valves).

Cam lobes, rocker arm faces, etc. all have hardened surfaces, and as such they don't wear a lot unless something is wrong (like lack of oil supply). The valve stem is pretty friggin' tough, too, so the chances of any of this wearing enough early in the engine's life, and hence opening up vavle clearances, is pretty remote - especially with today's metallurgy. On the other hand, aluminum is still softer than any of these other materials, and so the hardened vavle seat insert gets *hammered* down into the soft aluminum head until the aluminum in the area is sufficiently compressed and *work hardened* to resist any further pounding.

Valves can also tighten up early in an engine's life due to valve stem *stretching*, though again with today's materials this is rarely the case.

Now, after some time on the engine where everything gets *seated* and real familiar with each other, valve clearance flucuations should fall off to next to nil, and you'll reach a point where it seems like most of the valves are never out of spec. This of course assumes good quality lubrication and other parameters being in spec, okay?

As an engine gets older and older you may begine to see valve clearances opening up between checks. There are lots of possible reasons for this, but some of the more common ones are:

1.) Deposits building up on the valve seating areas and hence not allowing the valve to close all the way.

2.) The valve stem starting to *mushroom* a bit from repeated hammering by the rocker arm and/or cam, primarily because of too many heat cycles and the valve stem losing its hardness.

3.) Wear and tear on the cam lobes, rocker arm shafts, rocker arm faces, valve adjustment screws, etc.

To name just a few...

Now all of this has a ton to do with how you ride your bike, too. The *harder* you ride the bike early in its life the more likely you are to have lots of clearance with each valve adjustment. Also, the harder you ride your bike the better off you are erring on the loose side during adjusments, because you will be the rider that puts more heat in the engine and as such have everything expanding to its maximum size (which could cause valve clearances to tighten up to the point of hanging a valve slightly open and burning a valve or a seat...).

Conversely, the gentler a rider you are the more you can err on the tight side of valve adjustment to quiet the engine down, because you don't heat-soak the components as much...

Too tight valves are ALWAYS the worst case scenario. Lots can happen that's bad with valves clearances too tight... Whereas if the valves are too loose not much can happen bad except the engine is a bit noisier and you are losing a tiny, tiny amount of valve lift (reducing power a nano-whit or so...).

Ideally what you are shooting for is just enough clearance to allow for the heating of the components... i.e. You need some valve clearance when the engine is cold so that when everything heats up there is ALMOST zero clearance in the valve train... But then again, this all depends on how much heat your particular riding style and environment puts into the engine.

Me... I always err on the loose side with my valve adjustments - i.e. set them to the maximum allowable in the manufacturer's specs. I even use to dab in a bit more with air-cooled road race bikes that got smoking hot in our South Texas heat.

Symtoms of valves being too loose? More noise from the valve gear and a very, very slight loss of power.

Symtoms of valves being too tight? Engine is hard to start, hard to get a consistent idle with, high exhaust gas temps, a more significant loss of power, missing at higher RPM, more vibration, backfiring and spitting - especially on deceleration, elevated head temperatures, to name just a few.

Sorry this has run on so long, but it is a very critical subject.

However, if there is anything I have missed you need to ask about just let me know!

Cheers!

Allan (Dallara - The Rubber-Banned Man)

[taosports]

Thanks Allan for your most informative reply. You answered my questions and eased my mind.

[Ed K]

Yes, thanks Allan...thanks for sharing your expertise.

[Acacia]

Excellent coverage by Allen!! I agree - rather a little loose for all his reasons.

There is an area he did not allude to - and that is slight changes to the valve timing that is possible with various valve gaps and how this might affect types of performance.

[Dallara]

But I did, Brian (Acacia)...

I just didn't go into it in any detail, I did mention how you could lose some valve lift by having the valve clearances too loose, which also implies they would open slightly later and close slightly sooner.

However, with the cam lift profiles in use today the differences here are so minute as to almost be immeasureable.

Ideally, again, if you get the clearance *just right* for your riding style, conditions, etc. tehn the vavles should be quietest when you have the engine working the hardest you ever stretch it... Why? Because you have set the clearance where it goes damn near to nil when you have the engine at its peak operating temp and everything is expanded about as big as it can get.

If you get this right then you are actually operating with exactly the cam/valve timing the designer intended.

Cheers!

Allan (Dallara - The Rubber-Banned Man)

[Acacia]

Peak operating temperature on an air/oil cooled 50R?

Thermostat opening at about 180. From there it goes all the way to 230 if ridden hard - that is oil temp (that I see consistantly). Heads? Someone has used an infra red gauge and recorded 350 plus. Would be interesting to know the valve stem temp etc. I guess we are getting into the semantics - for street use. Stick with manufacturers gaps and all will be well.