entropy
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posted May 10, 2008 12:47 AM
running very skinny shims? CAUTION!!!
Y2K just tweaked my experimental head, sinking the seats to give me more PTV.
I was having a problematic time setting up the lash when i discovered that you cannot run shims less than about 1.40-1.45mm using Busa buckets and Ti retainers.
My shim kit goes down to 1.20 so i figured i had plenty margin telling Jim an exhaust target of max 1.50 shim
WRONG! The lil tit inside of the bucket isn't long enough to accommodate ultra skinny shims with Ti retainers.
Sooooo. i yanked the head, pulled the exh valves and took .010-.015" off the top of the retainers. Fixed it.
After tweaking the retainers, i could see what a fantastic job Jim had done w/the valve job he did for me.
exh range of shims is 1.38 - 1.48
int range of shims is 1.52 - 1.62
That's .004" range in shims!
BEAUTIFUL work by Competition CNC 
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aliveagain
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posted May 10, 2008 01:31 AM
So what may I ask did you use for this delicate procedure,file, belt sander?How did you hold it?
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VincentHill
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posted May 10, 2008 02:33 AM
I always took a little off the Valve Stem top! I used a Modified version of a Drill Bit Sharpner!
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entropy
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posted May 10, 2008 04:31 AM
Pete,
I gently held the retainer in a vice, put a fat (270) shim in the retainer which was about .014 under the top of the retainer, then filed down to the shim. Worked great, not too time consuming.
VH,
I didn't think of taking meat off the valve stem... Another trick to keep up my sleeve. Thanks!
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NOX
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posted May 10, 2008 06:28 AM
A quality shop will have a machine that is strictly for shaving the top of a valve....., i did a couple in my current stocker........
I have anywhere from 120 to 140 shims in mine, due to lapping. I had a couple that REALLY needed it bad, as I had two bent vavles in this head........
Its holding fine at 11,800 rpm
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aliveagain
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posted May 10, 2008 07:12 AM
Good info! When I had my valves done 2-3 years ago,the first shop talked of grinding the valve stem for clearance. I never heard of that and removed my head quickly from the shop and sent it to South Carolina.
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KZScott
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posted May 10, 2008 08:25 AM
 Edited By: KZScott on 10 May 2008 09:28
I believe its pretty common practise for places like APE to trim the valve stem when they do a seat job to keep the shims in the "normal" range... at least they do it for the older bikes. they probly do it on everything
VH, i have a "drill dr." i would be interested in seeing pics of your setup  you never know how far my shims will be out since i lapped the valves
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NOX
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posted May 10, 2008 08:32 AM
If you get it cocked, it could spit out the shim... Take it to a pro..........
It is a common practice
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Y2KZX12R
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posted May 10, 2008 03:03 PM
Edited By: Y2KZX12R on 10 May 2008 16:05
This is a situation most people would never run into.
Its more common to fly cut the pistons. But as you pointed out you did fly cut them and needed more.
We grind the tips of valves all the time for special applications but if you have the proper size shims its not needed. Grinding the tips is really a band-aid for not having the proper size shims, or wanting to reuse the same shims you had in there. Its not the prefered way to set valve clearance. On a lot of older 40's-50's stuff thats the only way to get the valve lash setup.
As far as grinding the valve tips for karls problem, it would make it worse.
The problem is the retainer hits the bottom of the bucket under a certain size shim. Cutting the tip of the valve would lower the shim and bucket even closer to the retainer the same as using a thinner shim.
another thing to watch for when grinding the tips is grinding too much. there is a 45* chamfer on the tip, you should not grind more than 50% of the chamfer which is about .003-.005".
So karl, whats the min shim with the KW TI retainers and BD valves with busa buckets in a zx12r head? Its good to know.
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entropy
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posted May 10, 2008 04:01 PM
hey Jim!
now that i think of it, as you point out, grinding the tip of the stem would not help... 
with Busa buckets, KW Ti retainers, ss oversized valves, the smallest shim you can use before getting nervous is about 1.50mm.
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aliveagain
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posted May 11, 2008 04:13 AM
How did you know the bucket was hitting the retainer and not the shim?Was it that noticeable when you put the shim in or was it multiple assembling with new shim with no result?
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VincentHill
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posted May 11, 2008 06:55 AM
Y2K I now understand what he problem was and I have had that also! In the Middle of the Night usually about 3 to 4 AM that is ALWAYS the problem that comes up!On my KZ1000 engine that had aluminun valve spring retainers I also had to shave the top of the retainer! The problem was, after doing that the valve was out of adjustment with a 2.0 Shim! I was using the small Honda SHims Yoshimura was using (Not much bigger that a large Pencil Eraser. I made a SHim Holder out of a TI Retainer and ground the 0.0100 off of the Shim. FOr the next race I ground the tip of the Valve Stem about 0.0200 and then was OK
Of COURSE Having a PROPER Machine Shop is ALWAYS preferrable but when it is time to go racing and none are open, NOT Going to the race is never an Option to me!
KZ Scott the kind of sharpner I had used an Angled stone at the end of the drill bit holes! I took it apart and turned the stone over to have the flat side up! The used the drill but size Hole that fit the Valve stem diameter and would turn it while I was grinding the stem top! It removed a few thou at a time which was all I needed.
Eventually I had to send the head to Ladd Porting in Elkridge Maryland to have the seats replaced. This was a head ported by Fujio Yoshimura at a time when Pops Was still doing a few heads and they agreed to do this when I was at Riverside road race where I earned my first National AMA Points in Road Race. What I am saying is that some heads are more Sacred than others!
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entropy
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posted May 11, 2008 09:18 AM
quote:
How did you know the bucket was hitting the retainer and not the shim?Was it that noticeable when you put the shim in or was it multiple assembling with new shim with no result?
that one...
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entropy
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posted May 11, 2008 09:24 AM
i do pay attention to lotsa stuff Vince says, but 2 really good builders told me:
UNDER NO FUKKEN CIRCUMSTANCES WHATEVER (except race day, no options) grind the top of the valve stems with anything but equipment made specifically for that task.
Apparently you risk of cracking the shim and all the fun & games that entails...
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NOX
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posted May 11, 2008 12:52 PM
That is why we had ours done by a pro.
We had a couple valves that were in perfect shape, but had some type of corrosion on the tip......., couple thou off and they looked like new........
I had forgotton why we did it.......
Too much motor building in too little time........
I did end up useing a range of like 120 to 140 shims, but forgot where......
Griding the valves yourself I would think would be a big no no........
quote:
This is a situation most people would never run into.
Its more common to fly cut the pistons. But as you pointed out you did fly cut them and needed more.
We grind the tips of valves all the time for special applications but if you have the proper size shims its not needed. Grinding the tips is really a band-aid for not having the proper size shims, or wanting to reuse the same shims you had in there. Its not the prefered way to set valve clearance. On a lot of older 40's-50's stuff thats the only way to get the valve lash setup.
As far as grinding the valve tips for karls problem, it would make it worse.
The problem is the retainer hits the bottom of the bucket under a certain size shim. Cutting the tip of the valve would lower the shim and bucket even closer to the retainer the same as using a thinner shim.
another thing to watch for when grinding the tips is grinding too much. there is a 45* chamfer on the tip, you should not grind more than 50% of the chamfer which is about .003-.005".
So karl, whats the min shim with the KW TI retainers and BD valves with busa buckets in a zx12r head? Its good to know.
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21 Runner-ups
2010 TMRC Super Street Points Champion
2010 PMRA Super Street #3 Points
2009 PMRA Super Street Points Runner-Up
6 Time Centerville Dragway Points Champion
Sponsored by:
Scorpion Helmets
Galfer Braking
AMSOIL
Steve's Speed Shop
Kawasaki Sports Center
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Y2KZX12R
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posted May 12, 2008 04:07 AM
quote:
That is why we had ours done by a pro.
We had a couple valves that were in perfect shape, but had some type of corrosion on the tip......., couple thou off and they looked like new........
I had forgotton why we did it.......
Too much motor building in too little time........
I did end up useing a range of like 120 to 140 shims, but forgot where......
Griding the valves yourself I would think would be a big no no........
Thats really the only reason you should grind the tips, is if they are a little roughed up and if a few thou doesnt clean it up replace the valve.
On a shim under bucket design the tips just dont get any wear happening in normal situations.
On a rocker arm engine where the rocker arm drags across the tip you will get some wear.
Thats when you MUST grind the tips to do a proper job.
Any good valve grinding machine will grind tips and faces and I personally would never grind a valve tip on anything but a valve grinding machine.
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VincentHill
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posted May 12, 2008 09:50 AM
I understand Everything everyone says! The fine stone used in the drill bit machines leaves a good finish and the engines I did this to ran the entire Daytona 200, Charlotte and Road Atlanta 75 mile road races. Same head and valves. Road Race is different from Drag race because the engine is used full power from low RPM to Max RPM and the over Revs on the down shifting. It may also be that the KZ1000 base engine is a brick to Kill and with only 2 valves in the head which were 6.5 mm diameter stems may allow for more abuse! All I know is what I did and that the bike finished all of the races and I ran in the top 6 to 15 place.
Did I mention that I also have a set of Seat Cutters that I used to cut all of my seats and had access to a valve grinding machine? I set my seats to be .75 mm wide on the intake about .5 mm from the edge of the intake valve and I set my exhaust seats 1 MM Wide about .75 MM from the edge of the valve. I also did not use valve guide seals on the exhaust side to allow some oil in the guide area to help cool the exhaust valve.
I had 2 heads and the endurance head had the valve guide slightly concave in top and the Sprint head had the tops of the guides slightly convex for less oil to the valve in the guides. The endurance engine used a little more oil than the Sprint engine and on the down shifts would you see a little smoke in the exhaust and 1 puff on the first part of Accel. This was how I made my engines live and they almost never broke (The Center bearing cap at Daytona the exception which I fixed by using a 1/2 inch thick plate to strenghten the cap!
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VincentHill
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posted May 12, 2008 09:56 AM
NOX you are correct about the Chamfer on the edges of the stem! I always added that back in as I did not want an edge to ht the Shim! Also remember the shims I was using were not a lot larger than the Valve stems tops! They were about9 to 10 MM in diameter and the Valves stem tops were 6.5 MM so not a lot of stress on the sides of the Shims
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