Bottom end of a 79' KZ650

Hi all i am new to the whole KZ thing, as i am about to pick up a 1979 KZ650 B. It needs a hone job and some piston rings, but what i am not sure about is the bottom end. I turns over nicely, but should i pull it apart and rebuild that as well? From what i have heard, is that these bikes are pretty bullet proof so is there any reason to mess with it?

oh it also has 19,000 miles on it.

A KZ650 with 19,000 miles is barely broken in. Just change the oil (use oil with the JASO-MA designation) and don't worry at all about the bottom end. Ed

Welcome Nicj. (everything 650ed just said)

My 79 runs great without engine work. Wondering what makes you think rings are necessary, is it a compression issue? If that good old bike has been sitting for years, chances are it needs to run and get oil to all areas, soaking gaskets and seals, freeing up rings, etc.

I agree, bottom end on the KZ650 should be fine. FYI common issue after a rebuild or head gasket replacement if the gasket is too thick or does not seal correctly you will have low compression and very hard to start and less power etc....So you can determine if ok simply by doing a compression check (after running it enough to break in the rings)
That all being said why are you replacing the rings and honing it? If it is only 19K you should just run it as is. I just restored a 78 SR and used a KZ750E motor with 20K on it and it runs strong and great compression. No need to rebuild until after 50K miles or more!

kzoldschooler wrote: I agree, bottom end on the KZ650 should be fine. FYI common issue after a rebuild or head gasket replacement if the gasket is too thick or does not seal correctly you will have low compression and very hard to start and less power etc....So you can determine if ok simply by doing a compression check (after running it enough to break in the rings)
That all being said why are you replacing the rings and honing it? If it is only 19K you should just run it as is. I just restored a 78 SR and used a KZ750E motor with 20K on it and it runs strong and great compression. No need to rebuild until after 50K miles or more!

+1 My KZ650 has 57,000 miles without ever having had any engine work done, and some have gone double that or more without ever pulling the cylinder head. Ed

Calling Ronkz650!!

I never can remember the numbers correctly, but I think he said 160,000 on one of his 650s.

Personally, I think his name should be "Cast Iron Butt Ron" :lol:

I have over 150,000 on this one. I have rebuilt the top end not cause it needed it but because I wanted to install the 810cc kit in it. I have about 15,000 on the 810 kit. What makes you think the top end needs work?

Sorry i didn't tell you this part. It needs rings and a hone job because i am buying it with the engine already torn half way apart. Lame i know. The top end is disassembled and there is some surface rust in the cylinders. I know everyone says stay away from the basket bikes but it is the only thing i could find in my area that wasn't over $1,500. The rest of the bike is in great shape though! Should i at least try and clean out the bottom end as good as I can? Thanks again for your replies.

If you don't know the history of the motor you have nothing to lose by pulling bottem end apart and checking everything out,like rod/main bearings and primary chain.
Theres probably a reason why the top end was torn down.

Thats kind of what i have been thinking too Plummen. The other option would be to clean it out as best as i can without splitting the bottom end, has anyone done this? Or would it be a waste of time to do it that way?

At least pull the oil pan and check for anything shiny/metallic in there.

With that info I would split the cases. You never kbow how the thing was stored with the top end off. Anything could hav egotten down into the bottom end.