NGC - Motorcycle content - amazing how valves and valve trains hold up

[ohiorider]

I had these two valves and valve spring on my desk, and thought I'd play with my new (to me) Motorola Turbo Droid camera.  Took pic, sent from phone to my email, moved it to Photobucket, copied URL and pasted into this post.  I'm getting better at this!  Although I think in the future I can eliminate a few steps in the process by going directly to Photobucket.

Anyway, these two valves came from my 1991 R100GS when I had the heads refreshed at 128,000 miles. I couldn't get a better close-up, but thought it might be good enough for some of you valve experts to see the wear on the valve faces, and comment about whether I needed to do the replacement.

Most amazing to me is just how strong the valve springs are ...... I could barely budge this one between my hands.  Hard to believe the valve train holds up in any engine, having to open and close valves thousands millions of times over this mileage.

Bob

[oldbike54]

 The number of times a valve bangs into its seat , the number of times a spring springs , and the number of times a spark plugs fires per mile ridden simply freaks me out  Don't even get me started on wheel bearings 

 Dusty

[SED]

We could calculate that with a few assumptions...

I get about 330 million valve closings!

if 60 mph is a mile a minute and the engine is turning 3500 rpm that means valve 1,750 closings/mile.

1,750 x 128,000 = 224,000,000 closings

But you probably spend some of your time in lower gears so there are actually more valve closings.  I approximated by assuming (that word again!) your bike probably averaged 40 mph with all the stops and starts and city driving and used that to estimate a multiplier:  60/40 = 1.5 so...

224,000,000 x 1.5 = 336,000,000 closings!  Cool! 

[Wayne Orwig]

Sometimes things don't go well. And it all goes wrong in a millisecond or two.

[Triple Jim]

The one that gets me most is envisioning pistons moving up and down 120 times per second (7,200 rpm), or with some engines, much faster than that.  Watch a 3,450 rpm electric motor spinning, and imaging a crankshaft and pistons connected to it going two or three times that speed.  Heck, just running down the road for hours on end at 3,600 rpm, the poor pistons are going up and down 60 times every second.

[ohiorider]

Wayne - some valve float and collision between valve and piston?  That must have brought things to an immediate stop.

[oldbike54]

 There was a calculation done a few years back by an engineer on an airhead forum re the wheel bearings used in that era . He calculated that with proper ( once every 50K miles) , the bearings would go a million miles 

 Dusty

[Triple Jim]

Wayne - some valve float and collision between valve and piston?  That must have brought things to an immediate stop.

It didn't when my 427 Chevy engine broke off a valve at about 7,000 rpm.  It kept on spinning for quite a while.  Once it had crunched up all the pieces that got in the way, it was free to spin again.   

[oldbike54]

It didn't when my 427 Chevy engine broke off a valve at about 7,000 rpm.  It kept on spinning for quite a while.  Once it had crunched up all the pieces that got in the way, it was free to spin again.   

 Pretty much what happened with my R60 , broke a valve , holed a piston , still running on one cylinder.

 Dusty

[Wayne Orwig]

Wayne - some valve float and collision between valve and piston?  That must have brought things to an immediate stop.

LONG story.
It was so violent that it broke a tooth on the rear pinion gear.

[Green1000S]

They don't.....

When I was a younger.... I "borrowed" (read: drove without permission) my dad's Citroen CX Pallas GTI and did several 220KM/H runs on highway, resulting in bent valves.
Few months later I asked my dad if I could borrow the car, he said no, pointing a burned and bent valve on his table. I asked what is that?
He said that is the valve from his Citroen.

I knew I was screwed and did not get his car for few years....
Moral to the story, valves are not amazing.

(and I have not learned a lot....still bending valves 30 years after my dad passed away)

Sorry dad.

[ohiorider]

LONG story.
It was so violent that it broke a tooth on the rear pinion gear.

Sounds a lot like when my 1972 Super Beetle decided to drop a valve.  It totally locked up the rear end for a couple of seconds until things freed up.  A valve head had broken off and jammed between the piston and cylinder head. I recall the back tires locking up for a few seconds  ...... before I had the chance to depress the clutch, the engine freed up.

And unlike today, I recall that a buddy of mine and I repaired the damage with a used piston, rod, cylinder, and head.  I think the used parts might have cost $50.00. 

There wasn't  much we couldn't fix back then!

[Moto]

The one that gets me most is envisioning pistons moving up and down 120 times per second (7,200 rpm), or with some engines, much faster than that.  Watch a 3,450 rpm electric motor spinning, and imaging a crankshaft and pistons connected to it going two or three times that speed.  Heck, just running down the road for hours on end at 3,600 rpm, the poor pistons are going up and down 60 times every second.

The one that gets me most is imagining two, hundred-kilometer-wide black holes each about 30 times our sun in mass spinning around each other at about 300 times per second. Makes valve trains look pretty ho hum.

[krglorioso]

Strange things happen;  In July, 1965, I was leading the intermediate class main event at a flat track race at Vista Speedway, Lanham, MD on my Triumph 500 twin.  Suddenly, a lap from the finish I had a single cylinder 250cc bike.  I finished second, very disappointed.  On tear-down, the right exhaust valve head had broken off and when the piston came back up it folded the valve head into the exhaust port.  The piston remained intact, tho nicked.  Repairs were limited to a new valve and piston, plus a light re-cut of the valve seat.

Wayne: per your photo, I suspect the engine with that valve in it lost the piston.  I think I came out the luckier.

Ralph

[Triple Jim]

The one that gets me most is imagining two, hundred-kilometer-wide black holes each about 30 times our sun in mass spinning around each other at about 300 times per second. Makes valve trains look pretty ho hum.

Yes, but black holes tend to stay together better than pistons.   

You're right... things like that in space are so amazing that they make everything we do on earth seem silly.