Hi guys im stuck what to do next with my ZX12 engine.

i bought it this time last year, fitted it and it runs great, however its using 1 litre of oild every 300 miles. so ive done a compression test which showed the 2 inner cylinders were at the min spec.

Today i stripped it down and had a look at the cylinders. all seems fine, no scoring and chipped pistons. Can i just buy 2 sets a rings and fit them to the inner pistons and re assemble? The problem i have is being as bike engine the cylinder walls are coated with a hardened finish so i cant hone them, im stuck lol. i dont know what to do next.

Any bike engine rebuilders here who can point me in the right direction.

Cheers
Andy

What about the oil stem seals?
Could be where the oil is leaking?
Darrren

i was under the impression it would smoke on start up but i can only see smoke when its hot and i rev it to the limiter in neutral and as the revs start to drop i see white smoke. its not the head gasket, oil and water arnt mixing. i cant zsee smoke when driving but i can smell it when i pull up to junctions.

From what you have said it does sound like it's burning the oil. It may be worth simply trying a thicker oil for high mileage engines.

Not a gauranteed fix but much cheaper than a rebuild.

Check the ring gap.

done it, manual says .25-.40 and i got .40.

checked the cylinder size and its ok too.

Just a thought

Did you check the bores for both taper and ovality ?

Check the oil control rings on the pistons ?

Did you try some oil down the bores and then re-test the compressions and note any differences ?

bores seem round, i added oil when doing the comp test and it raised the readings from 140 psi to 175 psi. so im sure its bore piston based. but i need to know if i can just replace the rings or do i need to deglaze the bores aswell, on a moddern bike engine which has some chrome type plating to the cylinders.

To answer your question, personally, I would put a set of rings in. Can't see it doing any harm, you'll just waste money on the rings and gasket set if it doesn't sort it. Think it will though.

Cheers

Rich