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Shim over/under bucket for racing
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JSBIRD69 View Drop Down
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Topic: Shim over/under bucket for racing
    Posted: 19 February 2009 at 5:24pm

I know this will come across as the most rookie of questions (and it is!), but after 35 years in aviation, my recent return to Jap bike drag racing leaves me with a few questions I haven't been able to fully answer or grasp the concept.

I have an 81 KZ1100 drag chassis already set up, and a complete 1992 KZ-Police engine on the way to me from California in the next week or so.
 
I plan to install the KZ Police engine to familiarize myself with the set up and installation, and look for another stock engine to modify from the bottom up.
 
I have an exploded view (Gawd, I hope I don't see that too often!) of the cylinder head, and will use that as my starting point.
 
If I understand correctly so far, the stock Z1/KZ head uses a shim under the retainer.
If the hot racing tip is to have the shim in another location in the stack, where exactly does it go, and what is the benefit?
 
Thanks for any knowledge you can share.
 
Jay
Poverty Level Racing - 1981 KZ1100 B1 Drag Chassis - 1983 GPz1100A Drag Engine
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Bob Brooks View Drop Down
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Posts: 102 		  Quote Bob Brooks Quote  Post ReplyReply Direct Link To This Post Posted: 19 February 2009 at 6:20pm
Hi Jay,
 All the early engines used the large shim on top of the bucket.Most racers change these for the Z650 style shim under bucket ( between the valve stem and bucket underside).
 Sorry but I don't know about your engine. Easiest way to find out would be to whip the cam cover off and have a peek and all will be plain to see.
 I definitely wouldn't ever consider running shim overs unless I had stock cams.
Hope you have fun.
Bob
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 19 February 2009 at 7:35pm
Thanks for your prompt reply Bob.
 
Can you tell me what the shim change is based on?
 
Is it for needed room?
 
Or is it having the shim weight suspended somehow desirable?
 
I have a lot to learn about these engines before I can figure on having any kind of success running them.
 
As soon as the trucking company calls to let me know my KZ1000 cop engine has arrived in Colorado, I'll go pick it up and then crack the cam cover to see what I have going on in there now.
 
Thanks!
 
Jay
Poverty Level Racing - 1981 KZ1100 B1 Drag Chassis - 1983 GPz1100A Drag Engine
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Posts: 803 		  Quote sonicrete Quote  Post ReplyReply Direct Link To This Post Posted: 19 February 2009 at 9:55pm
The valve clearance is adjusted using these shims. Effectively the shim is a thick $.50 piece on top the bucket under the cam. By using shims thicker or thinner the clearance is adjusted.
 
The KZ650 type uses a shim about the size of a dime located under the bucket. In this way it is a lot less reciprocating weight but more important the shim cannot get "thrown out" by over rev/valve float and the reason people do it. After a certain amount of "hot cam" it must be shim under or the cam will overlap and makes it a tiddly wink. It does a lot of damage to the head when it throws a shim so most people who drag race will not take the chance. 
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2009 at 1:12am
Thanks again for a very prompt reply!
 
OK, the lights are coming on, and the last post is going a long way toward progressing my Kawi engine education.
 
I know I'm in the right place, and the many years of performance and racing experience here are greatly appreciated!
 
Jay
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Posts: 102 		  Quote Bob Brooks Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2009 at 4:25am
Jay,
  You're welcome. I'm glad that our posts have helped. I think you might learn a lot by watching a racer build up a Kawasaki motor. They are very simple but there are lots of little "fixes" and "fiddles" that engine builders do but probably don't realise they're doing 'em! I'm not doubting your mechanical ability but you will pick up a lot of useful tips, and hopefully avoid potential disasters. All you have to do is find a willing racer. I'm in the UK, so unless you're on vacation then I'm out of the picture.
Bob 
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 20 February 2009 at 12:58pm
Bob, is that an invitation to visit? Be careful, I might just take you up on that!
 
I agree that finding an experienced and friendly local Kawi KZ engine builder is a best case senario, but I live 35 miles from the nearest city where such a person may exist.
 
I do have a factory service manual, and plan on using that for assembly and specification info, but also realize that there are certain subtleties in racing Kawi's to take into consideration.
I suppose that is when I'll be here again asking particular questions about subset assembly.
 
Thanks!
 
Jay
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Posts: 102 		  Quote Bob Brooks Quote  Post ReplyReply Direct Link To This Post Posted: 21 February 2009 at 4:06am
Jay,
 If you're in the UK then you are most welcome to visit my place. I might even machine you a part for your bike as a momento of your stay!
 
Bob Brooks
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 27 February 2009 at 1:18am
Thanks to all who have taken the time to reply to my rookie questions.
 
I have learned a lot in the last week or so, but still have a few things to work out.
 
I have a firm grasp on the shim under concept, but have a few more questions to those with the knowledge.
 
What other items in the valve spring well, other than the smaller diameter KZ650 shims, have to be changed when converting to shim under on a KZ1000?
 
Thanks.
 
Jay


Edited by JSBIRD69 - 27 February 2009 at 1:19am
Poverty Level Racing - 1981 KZ1100 B1 Drag Chassis - 1983 GPz1100A Drag Engine
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APE Jay View Drop Down
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Posts: 1710 		  Quote APE Jay Quote  Post ReplyReply Direct Link To This Post Posted: 27 February 2009 at 2:14am
Jay;
To change from shim on top top shim on bottom, you change the valve spring retainer and tappet/bucket
Kawasaki valve train parts

Good luck with the project.

Jay (too)
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 27 February 2009 at 3:39am
Thanks Jay!
 
You'll be hearing from me again! Smile
 
(Broke) Jay
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Posts: 803 		  Quote sonicrete Quote  Post ReplyReply Direct Link To This Post Posted: 27 February 2009 at 4:15pm
Key in www.aperaceparts.com and click on the KZ zone. There are a bunch of common ask questions and a list of parts.
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Posts: 1371 		  Quote riceburner Quote  Post ReplyReply Direct Link To This Post Posted: 27 February 2009 at 4:58pm
How big of camshafts are you planning on running?

Valve spring pressure is the key to keeping the shim where it belongs weather its on top or on the bottom. If the valves float the shim is going to come out.  

I always ran shim on top in the KZ motor.   
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2009 at 12:16am
Thanks Sonicrete...I've been to the KZ Zone quite a bit, but am suffering from a bit of info overload right now.
 
Thanks for your post, Steve.  You never had a 'shim on top' issue racing at your level? WOW!
 
Right now, based on what I know and want, this is where I'm headed...
1260cc
13:1
460-470 cams
Stage 1 J head
36mm carbs
 
Thanks to all for your valuable input.
 
Jay
Poverty Level Racing - 1981 KZ1100 B1 Drag Chassis - 1983 GPz1100A Drag Engine
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Posts: 6176 		  Quote Kawi1500Vortex2 Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2009 at 2:29pm
with cams that big its not a option - you need s.u.b. buckets
 
you will also need the correct amount of seat pressure
 
wanna see some arguments? ask whats correct...
 
tank
 
dead late don - dog house racing

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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2009 at 5:19pm
Thanks Tank!
 
I think I'll wait a few weeks to begin the seat pressure debate! Smile
 
Broke Jay
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Posts: 94 		  Quote KAWNOMAD Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2009 at 1:15am
You can run the shims above the bucket on bigger cams,just make sure when it spits the shim,and it will, that you recover the piece of the head that is blow off,so you can weld it back on to repair the head.    If i remember,420 and above should be under the bucket. Good luck
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2009 at 1:24am
Thanks for all the great replies to my questions.
 
I have it all worked out now and will be using the SUB on my engine.
 
Thanks.
 
Broke Jay 
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Posts: 94 		  Quote KAWNOMAD Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2009 at 1:33am
Earlier in your post you said you were going to build a motor from the ground up? It is of my opion that you can buy one for about a third of what it costs to build one  good luck
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Posts: 54 		  Quote JSBIRD69 Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2009 at 11:20pm
Hey Nomad...You're probably right.
 
But, then I wouldn't get the mental exercise, or learn the new many things associated with building my own powerplant. (Or make the mistakes)
 
Also, it's easier for me if I make a firm plan, then build it as I get the money.
I'm early retired, partially disabled and manage to live on less than $500 a month retirement income...and slowly am getting my machine together on those funds as well.
 
Thanks again for your input.
 
Broke Jay
Poverty Level Racing - 1981 KZ1100 B1 Drag Chassis - 1983 GPz1100A Drag Engine
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