TOPIC:

So i just bought my first Kawasaki Kz305. Its a 1987 Kz305-b2 and I bought it for $300 and it needs a new top end. The to of the engine was ran without oil pressure, so i am in need of a Cylinder head, cam and valve cover. I was searching online and i see lots of good parts for the early 80's models but not for the 87-88 models. In my research I found out that the 87-88 models have electronic ignition versus points like the older models had and the same 305 engine was used in the gpz305. I also discovered that the kz305 is basically just a bored out kz250. What's the difference between the cylinder head assemblies of my 87 and the earlier models? Would a top end from a '82 work on my '87? Would a top end from the gpz305 model fit? Is there a huge difference between the kz305 top end and the kz250?

First off I have no experience with the Kz200, 250, 305 other than what I have read on forums like this. What I can tell you is that once the top end of the KZ400 was redesigned in 1978 it was basically unchanged in the KZ400/440 line from then until it was done in 1985. Based on that I would suspect the same sort of thing for the KZ305 line - though there may have been changes to cam profiles, etc - especially with the gpz305. The KZ440 was changed from points to electronic ignition in 1981 but that does not matter much - either system will work on any of the bikes. I run the Kawasaki factory electronic ignition from the later 81+ models on my 76 KZ400 - it is a pretty easy retrofit.

I'd start by looking at the parts diagrams on the Kawasaki site, getting parts numbers and seeing if they match up between the different model years and the different models. You'll be golden if they are an exact match, otherwise you'll probably be in for plenty more research.

The 250 is a single, while the 305 is a Twin.
Partzilla is probably the easiest & fastest place to compare stuff.
From a quick visual comparison, I'd guess you can use the cylinder head from any KZ305. just a guess.
The 81 & 87 use the same cylinder head gasket.

Have you verified that it needs a new top end or are you just going by the seller's guess?
never believe anything the po says. people forget, don't know or lie. sad but true.

If the top end failed due to an oil issue the crank/rods may be toast as well. Splitting the crankcases to inspect everything is recommended...or purchase a good used engine.

I work at an Independent Custom Motorcycle shop and I've already taken the top end apart, the cam is burnt & out of specs, the cam bearings were obliterated and the cam journals are scored beyond repair. Definitely needs a new top end, not guessing. I have already tried the partzilla cross reference trick but I have found several discrepancies on their website in the past and have doubts that some of their information is 100% correct. I was hoping to find someone with some first hand knowledge and experience with these bikes.

G'day, well I'm probably the most regular poster on the KZ 305, not claiming to be an expert, there are plenty of experts on here, some of whom have already replied but generally there's not a lot of experience floating around on the relatively obscure 305.

I'd tend to agree with the others that the top end will more than likely bolt up just fine. Visually from the diagram it looks very similar, I think the 87 is a bit more angular around the fins but that's probably about it. My top end is fine so I haven't had to delve into that area too deeply. I know all about new pistons and rings if you need them!

I didn't know about the electronic ignition option until your post, so thanks for that. Could be an upgrade down the line if I have the need.