Shim bucket opinons

hey all, i wanna get everones opinion on what they would do if it was there bike. My bike is a 1980 kz 1000 1327cc with a J model head. Its got alot more done to it (see sig below). But anyway right now i got the head off the bike. I have been running psp 3x cams which are the same as the old andrews cams. They are a 418 lift. So far i have been running them with shim under buckets. Well iam tired of pulling cams to do valve adjustments. I want to go back to shim on tops. The question i have is should i take a chance and run these cams with shim on top. It says its the largest cam you can run with shim on top buckets. But also heard people talking about them spitting shims. I know that they usally do it at high rpms. I run a rev limiter set around 10 G if i remeber correctly. I would also keep a close eye on the clearances. The question i have is should i run these 3x cams or go back to stock? I have stock ones still. I would still like to have a hot cam but cant afford any right now. If Anyone has a set of good cams with lesser lift but still bigger than stock and would like to swap even up let me know. We could see if we could work something out. Thanks,Eric

The deal with spitting shims is that a very high lift cam will run across the shim and rock the edge of it in the groove that runs under it around the edge of the bucket.
This allows the opposite side to lift and they eventually flip out like tiddly winks if you are unlucky.
Before shim under, tuners used to fill the groove with silver solder etc to stop this happening and eventually you could buy performance buckets without the groove which seem to have totally disappeared now in favour of shim under items.
If your cam doesn't run that far over you will be ok.
It's easy to check for and sometimes you can actually see the shim lifting slightly when rotating the engine by hand.
Don't run tight valve clearances to compensate. It won't.
You want to be on the wide side for high lift cams. Yoshimura quote as wide as 0 .20mm for their ST cams .

I agree with zed1015. Also running high rpm s with tired valve springs on sot will likely spit especially when missing a shift ( don't ask ). If interested in swapping for a set of GPZ cams, let me know.

don

I always used Andrews 3X cams. With shim on top. With a 1075cc then 1260cc engine, for the dragbike. Keep all the parts good and tight, good springs. I set In. @.004 Ex. no more than .006. I shifted at no more than 9,000 rpm's.
You have no reason to go to 10,000. A waste of R's over the power band. I could never understand guys doing this??.
Nothing like the sound of 3X cams running about 1,500 rpm's, I always drove my bike all the way around the track. I did not tow it.
Just keep the valve clearence close. alot easier taking the cover off, than both cams out!
Here is an old picture I had.

So you guys think i should try running the shim over buckets. I was kinda leaning towards doing that myself. I got Aftermarket high lift springs. i cant remember excatly i think there up to a 450 or 460 lift. Also i think the rev limiter is at 10 but could be 9500, But i usally never hit it. Its just there in case. Just wanted everyone elses opinion. Thanks, Eric

I have a 1327 with mild 365 lift cams and shim over bucket and had it at max revs down gardener straight at phillip island. Still in one piece. :whistle:

From : Zed 1015.
The deal with spitting shims is that a very high lift cam will run across the shim and rock the edge of it in the groove that runs under it around the edge of the bucket.
This allows the opposite side to lift and they eventually flip out like tiddly winks if you are unlucky.

Makes a lot of sense and something that worried me since mine was built with shim over.
What size would be the maximin that you would advise for the slack shim over owners? :laugh: :laugh:
Thankyou.

zed1015 wrote: Don't run tight valve clearances to compensate. It won't.

z1kzonly wrote: Just keep the valve clearence close.

:huh:

Harvey1327 wrote: I have a 1327 with mild 365 lift cams and shim over bucket and had it at max revs down gardener straight at phillip island. Still in one piece. :whistle:

From : Zed 1015.
The deal with spitting shims is that a very high lift cam will run across the shim and rock the edge of it in the groove that runs under it around the edge of the bucket.
This allows the opposite side to lift and they eventually flip out like tiddly winks if you are unlucky.

Makes a lot of sense and something that worried me since mine was built with shim over.
What size would be the maximin that you would advise for the slack shim over owners? :laugh: :laugh:
Thankyou.

I always go no less than 0,10mm on std motors and 0,15mm to 0,18mm on the cammed ones.
It's the Bucket groove that is the culprit.
ALL cams recommended for shim over have almost the same max lift and that is direct relation to how far they travel towards the edge of the shim.
Once you are there a combination of very high revs, Valve float, and shim rock will set up the conditions to fire a shim out.
Get rid of that groove and the chances of a shim going awol is almost eliminated.

i will put the shim over buckets back in. I will have grind down my retainers first tho. Then i will put it back together and check out how far towards the edge they go. If they look to be to close i will just put stock ones back in.

Powerstroke_fan wrote: i will put the shim over buckets back in. I will have grind down my retainers first tho. Then i will put it back together and check out how far towards the edge they go. If they look to be to close i will just put stock ones back in.

OUCH! No No, Don't grind your retainers down.They are hardened. Change them. I know J heads are similar, if you need a set of stock Z1-KZ style I'll give them to you.

I silver solder my shim on top buckets . :ohmy: having done so since the mid 70's........I have never had a "shim spitter", some running with .460 lift cams on street engines :S . :pinch: taking the cams out for adjustment is a PITA :pinch: ..... Now a race engine that will see extreme RPM's on a regular basis is a different story . IMO, definitely shim on bottom. :dry:

Powerstroke_fan wrote: i will put the shim over buckets back in. I will have grind down my retainers first tho. Then i will put it back together and check out how far towards the edge they go. If they look to be to close i will just put stock ones back in.

If you have to grind down retainers head is not set up correctly period. now onto the shim under buckets if you have them keep them if you are having to adjust valves all the time there is a problem back to head not being set up properly to begin with as for shim on top buckets I have done Many with .425 lift cams W/O issue the key PROPER SET UP.