engine smokes after 807 big bore kit

so i have spent many hours over the last 2 years rebuilding my gpz750 r1 much money and cursing dealing with rip off merchants and finally finished her if that can ever be true. one small problem i have is she smokes badly really badly , i have built many zeds 750s 1100s and never had this problem before even though i have done more on this one than all the others ,they went reasonably smoothly teething troubles aside . this one has had a rebore with 807 pistons and rings valve guides seals ect so i am truely stumped as to the problem .ihave heard they may bed in so im using mineral oil for now but its not good riding with a blue cloud following behind lol im wondering if a build up of crankcase pressure is arising from the larger bores has anyone encountered this before after rebuild or big boring? HELP im going crazy.

over lapped oil rings on install.

yes but without doing so they were too big and they went in real nice mate thanks is definitely something to think about .have you experienced this before? i like definate answeres like that cheers.or do you mean they crossed themselves on entry because i spun it up quite a bit to check for scrape lines before fitting the head?.

Start playing engine detective!

1. First - oil coming from the crankcase breather? If you are running individual pod filters, then not a chance. If you are running with an air box (stock), then try disconnecting the little hose between the crankcase breather and the air box and see if smoke and oil are coming out of the engine there.

Make sure the crankcase breather isn't blocked! Engine running, place your finger over the breather hole - you should feel mild pressure pulses.

2. Is the oil getting past the piston rings? Not easy to determine, but if smoke and oil are coming out the crank breather with the engine warm, then this is likely the problem. Do a compression test and check that all the cylinders are within spec and all about the same. If you find one or all cylinders are low on compression, then something is wrong with the ring seal.

Who did the cylinder boring and honing? Did you check the work before assembly? Some people can do a good job of machining cylinders, some shouldn't even try!

An oil control ring assembled incorrectly (overlapped wave spacer, both rail rings on top or bottom, end gaps lined up, etc.) is very hard to determine without disassembling the engine, but if it is leaking badly enough, a tell tale sign of this would be pulling the spark plugs out and rapidly cranking the engine, repeatedly (no more than 30 seconds at a time, otherwise you could damage the starter solenoid, motor, and drive - give a minute for the starter to cool down before hitting it again). If oil starts spraying out of one or more of the spark plug holes - oil control ring problem. Use a piece of clean paper over each spark plug hole to see how much oil is spraying out.

3. If there is no smoke coming out of the breather, and the compression is good, then valves seals are my next guess. I am going to assume the valve guides are in good condition. Did you install high lift cams? One engine I have here came from a racer who didn't check to see if his big lift cams would clear the stock valve guides. The valve spring retainers hit the valve stem guides and crushed the valve seals, ruining them.

You need to find out if itsit's one cylinder or many that are burning oil. Check your plugs, if its just one cylinder then I'd put my money on the oil ring. If its multiple cylinders it could be a machining / fitment issue. An overlapped oil ring wont usually show up on a compression test.

yep true that mate compression is great i sent pistons and rings with cylinders and the engineers are best around here so got to check rings lol aarrrggg

thanks guys seems the oil rings are the problem as it runs through all answers ill keep ya posted now i think i hear the shed calling me to spanners cheers

yup you are the man stripped her down and your definitely right mate they shouldnt be lapped . wish i was on ere before builiding it coz i searched the net for how they went but only got may may not depending on shape of the ends which on mine looked like lappers but now ive tried em in the bores its so obvious so ive manipulated the ends to butt together better hopefully this will sort it im optimistic just waitin for head gasket now thanks mate

This explains it pretty well.
Steve

ok so ive rebuilt her again after creating a butting end to the oil rings and she doesnt smoke any where near as bad just a tiny bit which i put down to not being run in .thank you for the advise i really apreciate it mate good man

Bah wrote: ok so ive rebuilt her again after creating a butting end to the oil rings and she doesnt smoke any where near as bad just a tiny bit which i put down to not being run in .thank you for the advise i really apreciate it mate good man

I did one way better than that many years ago - maybe the second engine I ever put together, first being a 5 HP Briggs and Stratton - I think. I got impatient and used a wee bit too much force (murder by blunt force trauma?) to put the barrel down over the pistons on my 70's Honda CB Twin and actually broke a second ring and twisted one of the oil ring rails right out of the groove :sick: . It wasn't just burning oil, it was pumping it out of the crankcase!!! My step dad saw that and hid his tools from me for a while....