Burning oil

[johny brando]

If your valve stems ,guides & seals are all good ....turn to the barrel /bore n check the bore sizing & honing finish are they correct & then look at rings in particular ....check the free end gap is correct ( i.e. the open gap when rings are not in the bore ....could be deformed & too small so the rings are not hugging the bore tight enough ! ) check fitted ring gap sizes= 3 thou per inch of bore is a fair guide & there positions on Pistons i.e. all should have there gaps 180 degrees opposed to each other ( you can still have good compression but if an Oil scrapper ring gap in line with the above 2nd ring & then you'll burn oil alright ! ) Also check you have fitted your rings the right way up ....if thats wrong she'll burn oil too. Should have good barrel liner O-rings too, or oil can be drawn by capilary action up the outside of a barrel liners ...check them too.
Good luck ...one of the above will nail it. Johny B

Now then, on my little Z250 project which I completed 18 months ago, and ran very well and done 900 miles with no probs, in the last 50 miles or so its started smoking a fair bit, took out the plugs and one is very wet with oil, so took off the head, replaced the gasket, new 'o' rings, checked the valve seals, all seemed ok, put it back together, bugger me still doing it, what would be the most likely cause? Also in the last two lots of petrol I have put in a stabliser, if that makes any difference.

[DavidZ1R]

Well finally got round to stripping the engine down, took the barrel off and found the pistons to be lightly scored, when checking the ring gaps I found that they were very worn, the ring end gaps were well beyond the service limit, still had the old piston and rings which had done 10,000 miles, checked the ring gap and they were still well within the service limit, going back in! the bores are fine, the pistons other than light scoring still ok, also noticed the piston pins had wear, need new ones, only after 1000 miles! used castrol gtx, think I used the wrong oil, cant think what else is at fault.

[davejames]

David, are you sure that you are getting a good supply of oil to the top end ? These things were notorious for oil starvation problems when new. I went through 3 x cylinder heads and camshafts with one in 16 months. Put me off four strokes for 20 years

[z1bman]

it is worth replacing the nylon drive gear to the oil pump has these where notorious for failing & the cause of most top end seizures. make sure the steel shaft cannot be turned in the gear. hold the gear & try turning the shaft with a pair of grips if it turns it is scrap

[Big Fluff]

Well finally got round to stripping the engine down, took the barrel off and found the pistons to be lightly scored, when checking the ring gaps I found that they were very worn, the ring end gaps were well beyond the service limit, still had the old piston and rings which had done 10,000 miles, checked the ring gap and they were still well within the service limit, going back in! the bores are fine, the pistons other than light scoring still ok, also noticed the piston pins had wear, need new ones, only after 1000 miles! used castrol gtx, think I used the wrong oil, cant think what else is at fault.

Well if the ring end gaps are fine with the old rings in the bore, then I'd say you've been sold duff new rings!
As a general rule, piston to bore clearence should ideally be around 2 thou" with a 10 thou" ring end gap.
I have known rings to be marked incorrectly also, so chech with a magnifying glass that the rings are in the right way up, if theay aren't then this can really suck oil into the bores.

[DavidZ1R]

Called in to Z Power, spoke with the man, he told me alot about the z250, all the faults etc, the top end con rod is lubed by splash from below, oil starvation was a problem with this model, mainly the crank in early models, and the top end and cam, because of oil starvation, due in general to the oil gauze becoming blocked through poor servicing, the early cranks due to not being drilled right by Kawasaki early days, the piston pins are also worn, which surprised Dave, got new rings on way Will, will compare to the original set I still have, going to use a thicker oil to run in on, see how that goes. Wish I new what a crap engine the z250 was BEFORE I bought the feckin thing