Ever see valve float?

Started by Rikugun, June 18, 2012, 09:24:14 AM

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Rikugun

June 18, 2012, 09:24:14 AM
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

Rick G

#1
June 18, 2012, 03:49:23 PM
There not floating, everything is under control, float occurs when the valve train loose control .
When float occurs the exhaust note becomes ragged. Believe me I've been there.


I like BMW's finger adjusters , better than those dammed shims.Do these guys make sewing machines?
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

Rikugun

#2
June 18, 2012, 04:07:31 PM
Yes, I realize they're not floating but it's a catchy thread title and made you look.   :P  :)  And besides, how can you tell if they're floating or not!? They move so fast they eventually look like they're standing still!  :o  It's amazing to me the process evens works at those speeds.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

QBS

#3
June 18, 2012, 04:39:52 PM
Valve float definitely does not sound like not valve float.

Rikugun

#4
June 18, 2012, 08:34:34 PM Last Edit: June 18, 2012, 08:52:18 PM by Rikugun
Quote from: QBS on June 18, 2012, 04:39:52 PM
Valve float definitely does not sound like not valve float.

??? 

Rick, the 1980's Suzuki's GS1100 used a form of follower too with an adjustable screw tappet if memory serves. I think Honda used a form of follower on its (even older) DOHC 450 twin as well. They were supposed to have been a technological wonder and capable of considerably more than the tach indicated redline.  And neither required special tools or shim exchange.  :)
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

motoracer8

#5
June 18, 2012, 10:43:39 PM
 Cool video, I've never seen valve float, but i've heard it, felt it and have seen what happens when valves colide with pistons.
83 Vision and 11 others, Japanese, German and British

Rick G

#6
June 19, 2012, 12:41:15 AM
Thanks for linking to the video, I enjoyed it very much. If you think valve float is something, try floating the ports in a 2 stroke !!! ;D ;D ;D ;D ;D
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

Rikugun

#7
June 19, 2012, 08:09:30 AM Last Edit: June 19, 2012, 08:20:49 AM by Rikugun
Rick, glad you enjoyed it. It's really amazing to see just how much the keepers, springs, valves, etc. rotate.

Here's another interesting one that has animated engine types with a slide bar to control the speed and brief descriptions of the various cycles. If you speed up the 2 stroke demo you can actually see "port float" *

Motoracer, the valves aren't actually floating in the vids. They are spinning up the valve train to simulate their speed at engine redline. Engines are designed to run safely a bit higher than redline as a safety cushion and to accommodate weakening valve springs over the life of the engine.  I'm beginning to regret my thread title choice.... :(  :)  ;D


* Not really Q, just kidding  ;)  ;D


http://www.animatedengines.com/index.html
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

supervision

#8
June 19, 2012, 10:37:03 AM
  Thank's for the vid.  Those finger followers, are a giant step forward, think how much less weight, for the valve spring to cope with, that is, compared to big bucket and shim.  Plus, all you do, is slide the, spring loaded finger, by hand out of the way, to switch a shim.
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Rick G

#9
June 19, 2012, 09:05:45 PM
We used to have fun with newbys, by warning them "not to over rev it and float the ports"
I've had my first Vision to 11,500 rpm. The rev limiter cuts in at 12,000. When I shifted to 2nd gear it shot forward and  felt like is was going jump out from under me. Its not making more horsepower up there but there's lots of kinetic energy in the crank shaft.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

motoracer8

#10
June 19, 2012, 11:44:18 PM
Another thing that happens to valve trains is spring surge, it doesn't happen so much on motorcycle engines because valve sizes and spring pressures are a lot less. Where a motorcycle may have 65to90 lbs valve on the seat and 200 lbs full open a V8 like NASCAR uses has 200 lbs on the seat and 600 lbs full open, it takes a killer spring to keep 2 1/2" valves following the cam at 9500 rpm.

Spring surge is another interesting thing to watch, if I can find the video again I'll post it.
83 Vision and 11 others, Japanese, German and British

Rikugun

#11
June 20, 2012, 06:02:30 AM
Is this what you're talking about? Cork gaskets and pushrods.....how do they make them run so fast?  :D
http://www.youtube.com/watch?v=i_NpzU4pGjc
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

motoracer8

#12
June 20, 2012, 10:11:40 PM
Yep, that's not the video I was talking about but it's the same thing. Now that NASCAR engines are approaching 10,000 rpm that little spring bounce you see has become a real probblem.
When one of those guys slow way down but keep going its most likely he's broken a valve spring or rocker arm.

You should see the size of the push rods, but with 600 to 650 lbs on the nose of the cam part have to be strong.

Yes it is amazing that turn those engines 9000 to 10,000 rpm and last as long as they do.
83 Vision and 11 others, Japanese, German and British
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