TOPIC:

if you really want to do this kind of work you could either take your cylinder into a machine shop and have them mic up the bores and recommend some action. You may only need a precision hone to true the bores and then drop in a new set of rings or they may say that the bores are out enough to warrant a rebore and a new set of pistons.
The other option would be to buy yourself a dial bore gauge like this one.




$50.00 U.S. on flee bay plus shipping. If you do this you'll also need a 2-3" outside mic to set up the bore gauge. Also with the outside mic you can check your pistons and the difference between the 2 measurements is the piston/cylinder clearance.

Bores can wear out of round and just running a 3 stone hone through the bores will break the surface but if the bores are not round, it will take many thousands of miles to break in and seat a new set of rings. A precision hone will true the bores to within less than .0004" so breaking in the rings usually only takes a few high speed runs to seat the rings, and that's a whole process on it's own which is worth investigating if you've never looked into it.

Bottom line, if you're going to throw money into a rebuild, best spend the money wisely. Understand you're problem and decide which direction you need to go in to cure the problem.




I'm also a firm believer in leak down testing. It will ultimately tell you where you're losing cylinder pressure which will also tell you whether you're oil consumption is ring related or valve seal related. A lot of oil burning I believe is related to the valve stem seals for 2 reasons. First, the older style seals I believe are possibly nitrile or maybe viton and will harden from the exposure to heat. The newer silicone based valve seals will handle the heat a lot better. Second, if you look at the cylinder head and try to imagine the flow of oil in the head you'll realize that the valve seals sitting under the bucket shims are not flooded with oil like they would be in a rocker arm style cylinder head and as such the valve seals are not cooled by the oil like they would be in the rocker style head.

Hope this helps with your decision

KB

Speaking of valve seals, Crane Cams makes teflon seals for most applications and also offer generic-sized (chosen purely to fit the valve stem)teflon seals that come with their own little kit of tooling to machine to tops of the guides to fit the teflon seals. All you have to do is order seals that fit the valve stem diameter. Being teflon, they will handle the dry heat that Kawboy mentioned. And, they last longer than the valves and guides.

Everything else Kawboy mentioned is dead on right!

I too agree with advice above.

One of my last 1300's (1979) burned oil (27000 miles) so I decided to strip the top end over the winter to investigate.
The compressions were low too when measured. The pistons were all very good with no damage and within service dimensions.
The bores all looked ok with no scratches and no ridge at the top cylinder head mating surface. They were however very shiney.
The rings were slightly thin in width and the valve guide oil seals were all rock hard........probably the originals.

I managed to find a brand full new set of piston rings cheap on Ebay and bought them along with a low priced honing kit.
I practised the honing technique with my pillar drill on an old single bore before attempting the 6 bores themselves.
There are a few good videos on the web I found with good advice on this procedure worth watching.
I was very pleased with the way the honing tool worked and created a good matt finish even cross lattice surface on the bores.
New rings and valve seals fitted, the bike was back up to near the correct compression and after 1000 miles was spot on and burning a fraction of the oil it was before the work.

Its worth remembering that in the 70's and 80's, Kawasaki UK stated it was acceptable for a new 4 cylinder 4 stroke bike to burn up to 1 litre of oil per 1000 miles. As a young bike mechanic working in a multi franchise dealership then I saw many Jap bikes do just this, yet others burned virtually none at all. Obviously things have moved on radically since then !

A good measure to use for finding the root of oil burning is if you see smoke on accelleration......its piston rings / bores.
If its only on over-run and de-accelleration........its normally valve stem oil seals.
If its both.........you need the lot !


Pete F
UK

Thanks everyone for the info,
I will have to ask if the machine shop can do a precision hone, might get a funny look when asking,,
It's good to know that Pete F managed with a honing kit as well, I guess the bores were round enough for that.
I did a compression test and all the readings weren't too bad, between 145psi to about 155. And its wierd I can't even see any smoke from the exhaust but it uses too much oil that's for sure. The plugs are black and a trace of oil on the threads.
I might be taking a risk but I will be throwing these cylinders in the bin for two reasons. First I need to do this engine rebuild quickly as not using my own garage so will have spare cylinders ready to go on,second when I recently replaced the water pump seal I noticed the locating area for the seal was absolutely rotten because some idiot didn't use antifreeze in the past. Anyway the risk will come from using my existing pistons with another set of cylinders I have spare. I'm presuming the pistons are in good shape( haven't opened the engine yet)I know the spare cylinders look ok. Do you guys think I could get away with this, or is it a big No No?

I'm in the middle of a rebore job myself. My old engine had clouds of blue smoke coming out the back... and when I say clouds I mean you couldn't see behind you kind of cloud lol.

Anyhow... the rebore cost me $400 CAD, and the head work cost me $500. They reground my valves, seats, put new O rings in and cleaned up the casting marks on the intake and exhaust ports etc.

I have no idea of the precise measurements of the pistons but all of them were the same. I was concerned when I opened the box and saw the pistons/cylinders weren't marked...however the mechanic said they were all within spec.. but two of them just barely.