KZ900 A4 piston ring replacement\Cylinder Honing.

!976 Kz900 A4
54000 miles

I am about ready to take my engine apart and replace all the gaskets, seals and Piston Rings. Possibly even the cam bearings. I was wondering on when I replace the Piston Rings. I want to make sure I do everything right on that. What do I need to do to make sure everything comes out right. I'm assuming I need to hone the cylinders but what tools and techniques would you suggest for getting the best results on that? This is my first engine repair that I have done like this and so far don't have much invested in the whole project including the bike($100 bucks with a leaky carb). I am on a very tight budget but I want this bike to last me a while until my budget frees up. Please Help me out.

i hate to be the one to bring it up but since youre tearing the motor down that far and it has that many miles id suggest checking out the head since it will already be off anyway.a good cleanup with maybe a valvejob will get you many more trouble free miles,also check guides and new seals atleast.then theres theres the cam chain and parts to inspect while youre at it.as far as the pistons and rings go clean everything up and measure your pistons and bores before spending money on new rings goodluck,happy wrenching

It wouldn't hurt also to have your oil pump checked out during a tear-down! As previously stated, a good head reworking with new guides and a three angle valve seat cut would give you some long life insurance!

I guess I should go through the whole process to clarify. I am going to do a full tear down and cleaning every part in a solvent bath. The seal kit I'm puttin on has everything including new valve seals. I also already have the piston rings...Got them for Christmas.

I'm thinking about new cam bearings but they are out of my price range at the moment. I am going to talk to my buddy who buids trikes if he knows who can do my valves on the cheap. Luckily I'll be working out of his welding shop so that's going to help the project. He can also build me just about any custom part I need.

I'm going to have the frame media blasted and probably powder coated or high temp paint. Not sure which. Then polishing every external cover. And if I can find one for the right price I'm going to get a new exhaust or have straight pipes made for me.

I'm trying to do this on a super tight budget and can't get all the stuff I'd like to or I'd just get a whole new block with pistons(the 1015 set) and a new valve train. Unfortunately, that's just not in the cards.

I need to check around and see if anyone has some of the parts I need cheaper than z1. Those guys are and reasonably priced but still too high for me.

BTW is there anyone on here from around the Wichita KS area?

im about 2 hours north of ya in nebraska but ive been known to travel that area when its not covered in snow! :laugh:

not covered in snow.....I wish that storm last night was not nice.

we got the ice,then another 12" of white stuff to protect it! :laugh:

And from what I can see it's still going. Not fun for sure.

So I'm at the shop right now getting ready to pull the engine after some lunch. Not sure when I'm going to tear it apart hopefully soon. I have till the 6th off so I should be able to get a lot done with it.

At 54k miles, it would probably be money well spent to do a bore up 0.25mm and put in new pistons (along with a head job). Hone + rings will help a little but probably only for maybe 20k miles if that long.

Krusty,
Was/is this bike a runner? If so, then why do you want to re-ring it? Did you do a compression test? If you are tearing the engine completely down, then get a FSM and make sure that you measure everthing, cam lobe height, cam bearing journal diameter, cylinder diameter, cylinder roundness, cyclinder diameter taper, etc...

If your down on compression, then it means one of two things. The valves don't seal or the rings don't. The valve seat apperance will tell you alot about their sealing. If not sealing, then you'll see carbon tracks that run across the seat axially.

Usually if the rings don't seal, then it means that the bores are out of round, excessively tapered, are worn oversize, or are scored. None of these conditions will be fixed by simply replacing the rings. On a four stroke bike, the rings won't get stuck like a two stroke, and they don't normally collapse unless the engine got really hot, in which case you can expect scored cylinders. Just make sure that you measure everything, and if you can't then get a machinist to measure it properly. Hopefully it all works out, but I wouldn't have ordered any hard parts until I have seen their predicessor first hand.

Don't use them kit valve seals....!!! On my head/valve job, found they didn't last 2000 miles before started smoking....

On recent exhaust valve upgrades and new seals, in Larry's inspection, they where already hard thus not sealing correctly.

OEM seals are more expensive and will hold up especially if going into a performance head/engine.

www.Babbitts.com @ $9 each....

Sometimes you just have to bite the bullet and pay for the OEM components, no other way about it....

OMR

ok so I finally got the motor pulled and got the head off and the valves removed. Everything looks really good except for the valves and seats. Looks like it will need a valve job done to get it sealing properly again. Unfortunately I'm not sure where I can take in to get it done. Every place I call work on bikes. I'm almost wondering if I can just lap the valves and seats and get a good result. I really don't want to cut corners but not having the cash flow is pretty convincing reason to cut corners. Now I just need to clean the head and the valves to see what is really looks like.

It looks like the they cylinder are in fantastic shape. Everything looks smooth with no scratches or pitting. I think I lucked out on that and will be honing and reringing them at some point soon.

I will have pictures for you guys tomorrow. I forgot my camera at home this morning. Kind of a bummer.