Cylinder scoring

Wookie58 wrote:

daveo wrote:

The Graphogen must then coat everything as it dissolves and circulates through the motor...

Are certain oil change procedures recommended during and after engine break in?

I will leave that one for the guys much more familiar with these motors
 

I am all ears.  Bring it on!



 

Do you know what piston to cylinder wall clearance was ?
I just put a piston from my kz900 build now into cylinder to compare i post a pick .It has almost no movement ,but it is not connected to the rod so difficult to compare.
I used assembly lube on the skirts last time  .
It looks like maybe cylinders washed out running too rich or choke when started. was the rings and bores oiled ?

 

I have had great luck using General Motors  EOS  (Engine Oil Supplement )  as my assembly lube  along with  Moroso moly lube on plain bearings.
Have also lubed pistons and rings with Automatic transmission  fluid with great results
 

I didn’t personally measure the bore clearance, because I don’t have a means to do so accurately… I just dropped the cylinder block off at the machine shop along with the pistons and accompanying literature containing the specs, and assumed (possibly a mistake) that the job would have been performed correctly.

I guess I need to invest in a bore micrometer, to verify correct clearance.

When I assembled, I just wiped the bore down with motor oil.  I’d read somewhere to not use assembly lube on the pistons/bore as that may prevent rings from sealing.  Based on the feedback here so far, it sounds like that may have been a bad decision.

Also, since I had fitted a large oil cooler (from a ZR7), I cranked the engine without ignition (maybe 30 seconds) to “prime” the system and fill the empty oil cooler volume.  Maybe that was another bad idea?

I don't use assembly lube on cylinders or piston skirts.  Just plain motor oil.  The rings need friction in order to seat, and right after first start up is critical for this.  I'd be afraid that assembly lube would interfere with the seating process.

I use Red line assembly lube ,that is made for using on pistonskirts and bearings .Apply it only on the pistonskirts Dont use the assembly lube in the cylinderbore Light oiling the bores and rings before installing the piston into bore using pistonring compressor to minimize the risk of making scores on the rings.The assembly lube protect the first seconds at first startup then it will dissolve in the oil fast .I dont know your engine, but if it has a oilcooler fitted from factory the oilpump will make sure that the oil gets to the underside of pistons and to the cams and main bearings first.Some oil pumps are double making oil flow in separate channels .One passage flow to the oil cooler and another passage to the bearings.  Im guessing that the bore is to big making the piston rock. It can also bee that there was some debree in the bores when started ,but im not an expert.
You may also try to run it and it will not get worce,but do it on own risk.
You can use a borecope to check after a little more running.

There is several causes. I have built race winning auto engines for many years. There is always some wear on the thrust side of cylinder walls that happens during break in. This can be made worse if not enough plateau on the honing or it just to rough. I can’t tell a lot from your pictures but looks like there is vertical line on both sides of the walls. The lines are below the top travel of the ring stack ending at about the piston belly. So not ring clearance. Looks  pretty uniform, so not trash. So we are left with heat , pistons to wall clearance, or lubrication. Doesn’t look like heat, or at least not enough to cause molten metal transfer! Heat does close up wall clearance so that is one thing has to be considered with wall clearance. Piston to wall clearance can be tricky, different piston materials , manufacturing, engine type and use, may need there own clearance. Forged piston expand more with heat than a cast piston,, for example. Lubrication can be lack of or washed down . If you didn’t clean any of the pistons (in your pics)and looking at the walls above the ring pack area, doesn’t look like to much fuel except one cylinder has a little soot on on top of cylinder wall. I am not a kz expert we just played around a lot with them in our dealership and raced them mostly on the street. One thing I discovered on a kz was on a dry engine ,oil takes a long time to get from oil pan to pressure in oil galley(not just turn off light but 2-3lbs on a guage)on first start. So I ended up priming if a rebuild! I  always used gm E.O.S on cam and engine bearings and tranny fluid on cylinders and pistons back then! So if oil problem ,,correct and run it! If clearance problem,, hone to correct tolerance and run it! You can lightly sand pistons belly and skirt with 600 wet dry sand paper to knock of any high spots from scuffing ,,if need be! Make sure you always have air moving over the motor when it’s running (fan or riding) specially before it has some miles on it! Guess what I am getting at is looking at your pics , the motor is not f-Ed. Just saw the movie , side clearance and piston rocking doesn’t mean anything. There is no skirt on the side of a piston and some skirt designs can rock more than others.The ring stack has a much smaller diameter than the actual piston size. The piston belly (fattest part of the piston 90 degrees from piston pin )is the critical place to measure for clearance. You can check clearance by sliding a piston (long) feeler gage between piston and wall at the front of motor. This isn’t the most accurate way to measure ,but it’s would be close enough for this application. 

Sorry if this was already mentioned, but did you wash the cylinder walls down with soap and water to remove all the honing grit before assembly?  Wiping down the cylinders with a rag isn't sufficient to properly clean them before assembly.

I didn’t use soap and water specifically, but I did wipe down the bores with a paper towel soaked with carb cleaner, repeatedly until the towel came out clean.

Bcot, thanks for the information… regarding your observation about fueling that does bring up a good point.  The photos that I posted previously were taken after I had cleaned to take a closer look.  There was actually what appeared to be gummed fuel on the pistons that I wiped off.  I only took one photo of that, but all cylinders were in roughly the same condition.    

It looks like the cylinders was washed out  with too much fuel / choke .Carbleaner is not enough to clean the bores .To get the bores clean you must use hot dish  soapy water and brush .Do it several times then .wipe them clean with wd 40  or transmission oil  and white lint free cloth until the cloth is clean.After washing the bores must be oiled /cleaned with wd 40 imidiatly  because they will start to rust in minutes .

Agree with bore brush and hot soapy water. Forget not everyone has a jet washer.  Wiping with brake clean will get the big stuff, and to be honest the fine micro grit that gets trapped in the cross hatch is harder on the rings  than the pistons.. looks like it was rich and could cause some washing down of the walls. I just wonder why it looks like it has the same  marks on the thrust side as the non thrust side. It has a lot of carbon on the piston for that little of running and I can’t really see how bad the wear marks on the cylinders really are. Sometimes the camera makes them look worse than in person .If you can feel those lines I would check piston to wall clearance. Washed cylinders can show some wear on pistons and walls but again usually harder on rings and the cylinders .. Just doesn’t  look worn at all above where the piston belly stops. If the lines are just marks (staining) and can’t be felt could just have been carbon falling off top of cylinder and piston and getting between the cylinders and piston creating the appearance of scoring. I have seen that. If it was mine  I would pull the cylinders check piston clearance at top and bottom of cylinder(bore gauge feeler gauge doesn’t matter) check piston manufacturer spec, if there after market pistons, not Kawasaki specs. I like at least.002” for a cast piston more for forged. If ok ,,I would run a bead hone through it a couple of times, meaning up and down the cylinders 2 or 3 times, lightly 600 grit the piston skirts if they have any marks you can feel. clean every thing up in hot soapy water really well. Oil everything up with some 20w50 full synthetic just as assembly lube ‘not in the pan. Fix the rich fuel issue. Clean carbs, check floats float level needle and seat choke plunger seal (if this bike has that style of choke, not sure) put it together and run it. That’s all if you can feel the marks in the cylinders. If it’s just marks from carbon, run it. Ok now anti synthetic people! Agreed synthetic oil can hamper some rings from seating. But it resists getting washed of cylinders and the motor has already ran  maybe in a harsh ring environment. I don’t use sticky thick assembly lube on cylinders or piston  because it traps the metal particles from break in in the cross hatch of the cylinder walls and ring lands.That’s just what I would do. Like I said not a kz expert!!!