Jesse's kit never really took off as I can remember, however. APE sell a simple valve spring retainer kit which has deeper shim pockets and do not require "custom" shims. The APE kit was used in 1340 GSXR project bike done is drag bike magazine. The APW retainers were used with a WEB .380" cam and 40mm Mikuni's. The bike put out 171 horsepower at the rear wheel using DynoJet 250 rolling road dyno. There was no mention of a shim popping out during the article at any time.

 

I guess I'll have to look into that too then. It's just curiosity really as I already have a 90 head and an 88 head for the hybrid build but I always thought that somebody had to have come up for a fix for this head. I mean a lot of other bikes run shim heads and don't have this problem - my ZX9R among them - so there has to be some sort of fix for it. Plus, from what I understand it flows better than the 90 head - or am I wrong on that one?

 

The reason "other" shim style heads don't seem to have this problem is due to the "other" shim head design. "Shim Under Bucket" trapps the shim under the bucket and on top of the valve stim, the shim can't come out. Kawasaki's used a "shim on bucket" as the 91-92 GSXR head, but with down draft heads. They were able to get the indiviual rocker arm(s) geometry done in a way it exerts better control of the shim puck. Also, they may use a deeper shim retainer design as had to be adopted to the GSXR. Also remember, that head was only used for two years and even Yoshimura resorted to using "forked rocker arms" when used in Superbike. Even if the shim stayed in place, Yoshimura claimed the rocker arm pad would break up, this has accured on more then one Kawasaki also when high lift .400" cams were used. I believe anything over a .380" lift cam, can't be used with the shim head. I looked at the current Yoshimura Stage one cam for that head and the lift is .375". In the past, the Superbike lift's for GSXR's were in the .380-.400" zone.... I think the APE kit is way to go if you had to use the head. The price is less then $10.00 greater then the regular retainers and they are made of Titanium also.

 

Best solution, find an 88-89 750 head and forget the shims.... or even an 89-90 1100 head... parts is parts...

 

I have a 750 so a 88-89 head will only work with a 88-89 block - which I also have and intend to build a hybrid out of with my spare 87 bottom end. I also have a 90 head that I am going to use on my other 87 engine but that one is going to get a big bore kit. I was only curious on the subject is all. I don't really intend to buy a 91-92 head. But, I have to admit, they are considerably less expensive than the 88-89 or the 90 head so if they can be fixed, there could be something there for somebody else that may have an extra 91-92 head laying around collecting dust.

Truth be told, Marko has a few and I told him a while back that I was going to look into this and let him know what I found out, but I didn't really find out much so I posted it here. Now I know more, and so will he. :biggrin

 

good find eric! and thanks rajay for the information on the deeper pocket shim retainers from APE!

i had an 86 750 engine with a 91 head and it was very, very strong. yes, it did spit two shims, broke two rocker arms, damaged the piston and left me stranded. would i do it again? not sure...mostly because i do not like the added effort of valve adjustments. if i do, i will definitely go with the APE kit.

 

When I decided to put a hotter cam in my 91 1100, I just converted the head over to the older fork style rockers rather than deal with the shim spitting issue.
It's not difficult to do, but you'll need parts from an earlier head, and there is some grinding for clearance. I got the parts from an 88 750 head which I had intended to simply replace my 91 head with, but the guy I bought it from never did find the cam journal caps. :hammer It seems they are matched to the head.