GPZ/ZR 550 Cam Cover Design & Compatibility

I have a 1990 ZR550 Zephyr project bike that I’m working on. It came to me with the cam cover loose, just sitting on top of the engine with no gasket. I got a gasket, and I could just use the cover I have. But I want to do what I did on my other bike which is to replace the cover with a Euro-spec cover because it eliminates the porting for the PAIR valve emissions equipment, for a cleaner look. 

This time I wanted to use a GPZ550 cover because it has the “DOHC” on it and I think generally looks cooler. I already got one, but just realized that the swap is not entirely straight forward. Aside from any other issues, which I am curious if anyone knows of any additional pitfalls in this plan, I realized that the cam plugs are different. Here’s some photos to show it.


 

 

The first photo is the GPZ550 with the “DOHC” cover and the second photo is my actual ZR550 with its Euro-spec cover. You’ll notice that the cam plugs are different, the GPZ has a half-circle that looks like it might just be rubber, and the ZR has a full circle that is alloy. 

So what does anyone know about this? First of all is there some performance reason for it? The ZR is a newer version of the engine used in the GPZ, so is it some kind of improvement to sealing it up, or just aesthetic? Could I just get some GPZ half-circle plugs and be done?  Any other potential issues I’m dealing with here? 

Worst case scenario I sell the GPZ cover and just get a proper ZR, but I’d love to make this work if possible. 

The gaskets are different PN's.  That suggests the cover and head screw pattern are different as well.

That could just be because of the same reason though, couldn't it? There's a slight notch in the gasket where the plug in the ZR plug is, but you wouldn't need that on the GPZ. 

It could just be the photo's but the GPZ cover looks to be a different shape at the ends over the cam plugs ( Zephyr looks more square)

I’m researching it more and noticing the same thing. Starting to feel like my plan might not work out. 

Worth doing the research (cam profiles, valve size etc) there may be performance gains to be had with a complete "head swop" 

I know folks have swapped in GPZ550 cams in their Zephyrs for more top end speed, I think someone in this forum did it. I’m fine with the mid-range tuning of the stock cams. I was just chasing the aesthetic. 

Stereordinary wrote:

I know folks have swapped in GPZ550 cams in their Zephyrs for more top end speed, I think someone in this forum did it. I’m fine with the mid-range tuning of the stock cams. I was just chasing the aesthetic. 

My thought process was that a head swop (if viable) would give the aesthetic but possibly the added bonus of performance improvement 

-I own a Zeph 750, and even the valve cover gasket of the KZ750 was different.   Would not fit, would not align, would not cover the areas the stock would.  I also have a valve cover of a KZ650....a gift from somebody,...and won't even come close.      Basically the perifery of the heads are similar but different. 

......and I did not care for looks, was only interested in the KZ750 gasket because it is a lot let expensive than the factory for the Zeph 750.

In the next week or so will be checking the valve clearences on the Zephur 550 i got reasently. I will test fit my Z500 spare cam cover and get some pics for you. the older GT550 shaftys have the "DOHC" on them too.

rob B
UK

That would be great Rob, thanks!

linuxrob wrote:

In the next week or so will be checking the valve clearences on the Zephur 550 i got reasently. I will test fit my Z500 spare cam cover and get some pics for you.

Hi Rob, any chance you had an opportunity to look at those valve covers?