Hoping for some informed and considered ideas, so please help if you can. Rebuilding my Zephyr 750 since January and heres the latest problem. Bought a new gasket set and a new set of genuine Kawa piston rings, standard size.

So, whipped the head and barrels off, cleaned all the old gasket off carefully and then replaced the piston rings (in the correct order, with the gaps offset like it says in the book), stripped out the valves and replaced the valve stem seals with new ones then rebuilt the head.

new gaskets, new valve seals, new rings, new 'o' rings!!!!!!!!

Put the whole lot together, torqued down to the correct pressure in the correct pattern: carbs back on, headers, coils etc etc.

She fired up after a few attempts and some tweaks of the carbs and about 30 seconds after starting she starts puffing white/grey smoke from the exhaust pipe and not firing on cylinder 3.

Replaced the plug on 3 and now its fine on 3.  but the smoke continues!

Pulled the plug from cylinder number 1, and its clean and sparking.  Yeah, i did say CLEAN.  Black oil seeping from exhaust joint and oil spraying from end-can over the swingarm????????

So, seems to me like its taking oil into cylinder 1 and preventing firing cos the downtube is only just warm.  getting pops and bangs too from same exhaust tube too.

I really really really want my Zeph back on the road, help please.

Duke                                                                                                                                                                             

sounds like you'll have to pull it down again Duke                                                                                                                                                                             

Did you deglazes the bores ? if not it may be the rings are not sealing just try doing a compression test across all cylinders.
                                                                                                                                                                             

Are the pistons standard size? If you fitted STD size rings to oversize pistons, that would cause smoking.                                                                                                                                                                             

I agree with JP. Do a compression test before anything else.                                                                                                                                                                             

sounds like smoke is due to incorrect valve timing ,cant see how oil is coming out of exhaust with out fouling up the plug !unless the valve clearence is too tight or none at all,the other thing is ---have you broken a oil ring ? i think you need to strip it down again .[all the pistons should be the same size ] chris                                                                                                                                                                             

Thanks for replies so far.

Yeah there has to be another strip down; the most likely culprit i think is that i might have snapped a ring or two.

Just to clarify, the bike was running fine last year, apart from a small oil leak and some cosmetic changes i wanted to make.  The first engine rebuild then resulted in a bent ring (so i had to buy a set of rings for that piston) then i rebuilt the engine to find smoke coming from either piston 1 or 2.

Last weekend, when we took the barrels off we found a broken ring on piston 1.  split into 3 bits but all still in the groove.  So the question is, did we break it during the rebuild or has it broken somehow when i ran the engine.

Answers to other points: don't have a compression tester, all pistons are standard, valve timing is spot on and 2,3 and 4 seem to be happy enough to do the pop, whizz bang business without any probs.                                                                                                                                                                             

hi, never seen a piston ring break in a four stroke engine of its own accord , you do need to deglaze the bores with a 600 wet and dry paper but not doing that would not cause your probs .also using a piston ring in each bore check the wear by checking the the ring gap as a  rule gap should be about 2 thou per inch of diam,but check with your particular model . you nead to use four piston ring clamps if its not easy to slide the cylinder onto the pistons you aint got it right . hope this helps . chris" retired m/c mechanic "                                                                                                                                                                             

You can hire a deglazer from hire shops that goes in your drill plenty of oil and a few mins per bore will give you a much better finish than by hand with wet and dry you will be able to hire ring compressors aswell                                                                                                                                                                              

Check the ring gap at the top of the bore aswell as about a third down. The rings don't reach the top so that measurement will be unworn and the one further down will have the wear.

Have you broken an oil scraper ring? The one lowest down on the piston with sideways holes in it, also remove valve springs and seals and try to wobble the valves. A worn guide or valve stem will do this, especialy check the exhaust valve if there are signs of oil.

I am assuming you don't have access to micrometers etc.

Check the bores and piston sides for scratching or gouging from the broken rings too, and the small end bearings for signs of wear or if one flops about more than the others.

mark, mechanical engineer.

JP-yeah, was thinking of just buying one of those deglazers anyway, will try it when we get the head off again.   XJ-did the wobble test when i replaced the valve seals and all seemed to be within tolerance but i will check the bores like you and CHRISTOF have pointed out.Don't have a micrometer.  Didnt have any problems with the oil ring, they assemble andf slide in pretty easily, its the other two rings that are a bugger.  i use large width cable ties to compress the rings-works well.   Thanks for the help guys, no work this weekend cos i'm off to Wales tomorrow but will keep you posted.   Duke                                                                                                                                                                             

WOOOOOHOOOOOOOO BRUM BRUM BRUM NNNNNNYYYAAaaaaaaaaaaaaaaaaaaaaaaa brum brum brum

All sorted now, hopefully.  as of today its all back together.  It needed another strip down and fitted new valve stem seals, new piston rings and new gaskets all round.

Put it all together yesterday, checked and double checked everything, fired it up but still getting lots of smoke from cylinders 1&2.  Turns out it was just old oil, carbon and crap in the exhaust tubes which needed to burn off.  Got the carbs balanced this afternoon, adjusted the throttle cables etc and now it starts on the button, bit of choke for 2 mins then settles into a steady tickover at about 1200 revs (bit high i know; but i'll settle for that right now).

Just a few other adjustments tomorrow and i can take her for a spin.

Thanks for all the help and guidance chaps.  will post a few pics when we next get some sunshine.

Duke

                                                                                                                                                                             

 grrrrrrrrrr fer ferkin sakes

anyone want a Zephyr?                                                                                                                                                                             

That don't sound good what happened
                                                                                                                                                                             

OK quick update and to cut a long story short:

No.1 mistake-i didnt check the integrity of the oil filter back in December when i rebuilt the engine, subsequently i suspected oil starvation to the top of the engine which caused over heating and some damage to the cams.  

No.2 mistake- thinking i had solved the prob with a new filter.  The damage was much more widespread resulting in a big end failure, smashed piston, cracked crankcase and probably bent conrod.  Engine is totally written off.

Happily, managed to find a replacement engine which will hopefully arrive next week.  I am gonna beaT THIS BIKE INTO SUBMISSION IF IT KILLS ME, IT WILL PLAY BALL, IT WILL SUBMIT TO MY SUPERIOR INTELLECT.

Second happy point is the engine was cheapish and getting delivered to the door on a pallet.

Tune in next time folks for more derring-do and other nonsense!                                                                                                                                                                             

Just realised i aint updated this thread for a while.   OK, the engine arrived, was cleaned and painted, new oil and new filter and it slipped into the frame with very little effort, snags or damage!  Looking good.   Fired it up, balanced the carbs, felt that the silencers i been trying to use might be causing all the runninig problems so managed to source the originals from the net (for £80 the pair ), got them onto the bike.  This took a bit of welding and some flexible exhaust tube.   Been riding it all summer....wooohoooo without any further problems but i feel it may be running a little lean, so might have to fiddle with the carbs a bit.   Unfortunately, just the other day, the flexible tube got a bit too flexible and bloody well split!!  So its under cover for the mo, maybe over the winter i will source the original downpipes and get my local garage to sort them out for me.  So thats it for now for the Zephyr.   Just have to ride my ZZR1100 in the meantime.   Oh and i am gonna start restoring the GPz900 in my garage over the winter too.  Anyone wanna give me a hand, just drop me a line.  I always have tea/coffee/biscuits and a drop of single malt aroung the place.                                                                                                                                                                             

Hey DukeZ,

Sorry to hear you've been having so much trouble with your Zeph! Those old air/oil cooled Kawasaki fours are renowned for being pretty bulletproof units so it's a bit of a surprise. Anyway, the reason I thought I'd jump in here is that I've got a GT550 (ugly cousin - same engine, shorter stroke) and I'm aware that at some point it'll need new rings, etc (drinks about half a pint of oil between Lincoln and north wales tough it still goes like stink) Are oversize rings/pistons available for these old kwak engines? Where did you get yours from?

Hope you get your flexi sorted soon, and if you need any parts, I know a guy who's got a collection of various kawasakis in bits.

Have a good un,

~D

Hi Impy   I think i got rings from z-power in Leigh; they really know their stuff on zeds.  its really local for me (2 miles).  They have been featured in loads of bike mags and can usually supply parts within a few days and are always really helpful.   heres the weblink.   https://www.z-power.co.uk/merchantmanager/   Hope thats of some use to ya.   Ride safe buddy.   Tom                                                                                                                                                                             

Added the link to my bookmarks - I may or may not need some selector prongs for my gearbox soon depending on what I find when I have the box to pieces... so the information could be really helpful!

Thanks! and I know Leigh well:)

~D