00 kx 250 scratches on intake side of piston lines on the intake bridge of cylinder

[bigred455]

Does anyone else notice what their pistons look like on the intake side.?With the oem plating i was getting scratches on the piston, the cylinder had corresponding line's ,But the cylinder was smooth If you are looking at the piston in your hand,from the intake side, the scratches were showing up on the left side, and right side ,the left side is more prominate,where it rides on the intake part of the bridge on the cylinder.I gap my rings also,If you look at the ring locating pin it is in line with that,But it is not just 1 scratch,The scratches are the same width of the intake bridge about 1/4 inch wide, starting below the bottom ring and they run to the bottom of the cutaway on the piston..I had my cylinder replated a while ago I did a top end on it and i had the same scratches on the piston,but they were a little heavier,and the same lines on the cylinder as before,but they were light brown ,I am thinking maybe because the plating is stronger than KAWA'S PLATING and the way the piston intake rides on the 2 narrow bridges(LEFT AND RIGHT SIDE OF THE INTAKE) Looking at the cylinder through the exhaust port,look to the right where the locating pin rides on the bridge that is where i am talking about. The left intake bridge looking at it through The exhaust port,You can see the lines on the cylinder,but not as bad.The lines have a light brown color to it only on the right side.. The piston left intake side will line up with it Just like before .The only difference is i have that light brown color to the lines on the intake bridge.Well what does any one think,do you think kx's huge intake in the center and the narrow 2 bridges on the side where both the ring gaps would ride have anything to do with it.Trust me it is not dirt I went through this before,My jetting is nearly perfect The first piston i took out after the replate had a beautiful burn pattern, The exhaust side of the piston and the sides of the piston look perfect.I have 5 hrs on this piston, I figured let's take a look at the cylinder again through the exhaust port and drive myself crazy, the cylinder looks the same.Every thing else in the motor is within spec.My bike runs sweet,Compression reads 225LBS.Maintainence do i need to tell how I am.? What do you guy's think, maybe the way kawa has the huge intake port,and the 2 narrow bridges on the side where the ring locating pin would ride seems to be the cause.I am going to run it anyway,I am kind of going out of my mind trying to figure this out. I don't think you can get away from it because the design of the intake side of the cylinder.

 

[flyinfish]

Same here

I have the same marks on my '03 kx 250 cylinder. Mine aren't as pronounced as yours seems to be but I have only about 80 hours on this cylinder. I'm guessing it's a flaw in the design that causes these lines on the piston and cylinder. I agree that the massive intake port leaves only two thin bridges to bare the load. Perhaps these are hot spots due to the design. I'm going with a Wiseco piston this time to see if it wears less...I just hope my cylinder doesn't wear more!

T.J. :ohmy:

 

[kdxtodd]

I noticed scratchs on the exhaust side of the piston too, but I new it was just plating flaking. It was a wiseco piston so it will probably still have scratches.

 

[mikecaldera]

Can u say Carb?

Scratches are 99.99 percent caused by dirty air filter. Even if u change daily!

Assuming no widening of your intake ports or removal of top ports....


Clean that Airfilter and give it a PIG bath in pj1 or premix oil!!!


hope this helps

mike

 

[mikecaldera]

deburr ports lightly to give rings proper seat, not 90degrees

deburr, chamfer ports lightly to give rings proper seat, not 90degrees.

225 psi...holy jet fuel batman.

milled the head hard i see.

polish the exhaust w/ dremel and proper bit, emery cloth 600 for port edges.

your piston rings are smacking the ports hard.

I'd help you but eric gorr can fix it.

 

[bigred455]

deburr, chamfer ports lightly to give rings proper seat, not 90degrees.

225 psi...holy jet fuel batman.

milled the head hard i see.

polish the exhaust w/ dremel and proper bit, emery cloth 600 for port edges.

your piston rings are smacking the ports hard.

I'd help you but eric gorr can fix it.

225 is stock on the 00 kx250 believe it or not,The problem is not with the chamfering of the port's .I use rubber bullets(cratex) to chamfer my port's CMF. It was a pretty simple answer what was causing the vertical scratches. I am always looking over the easy solutions. I have found out that if I premix 32:1 the scratches are not present starting with a new piston. I have a 03 I was using the Klotz R-50 at 40:1 and no scratches,but if you look very, very close, they were very vague but I was happy. I ran the mx2t at 32:1 and the piston was even better beautiful no scratches whatsoever,but I thought the crank was a little dry. I ran the amsoil at 50:1 and the intake side of the piston looked horrible,the crank was coated excellent and I do mean excellent,but the more I cut the oil ratio the worse it gets.Maxima 927 at 36:1 the piston looked great,also. I never did mention this,but in the past when using yamalube 2-r I never had this problem mixing 32:1.I have used other oils also at 40:1 with slight scratching
THE PROBLEM IS OIL RELATED AND THE KX PORT LAYOUT ,NOT QUALITY,but quanity of oil!!!!! Not all KX 250 owners are going to see these scratches,It depends on how you ride. I have bashed people on here with their 20:1 Ratio's :bang:exaggerated, they are not far off!!!!!! That brings me to my next statement,how the heck can a oil company recommend A 50:1 ratio not knowing what size motor,how it is being used(rpms being usedand style of riding).I will say this for my riding conditions 32:1 is the ticket. I am thinking about trying the amsoil again at 32:1 I was really impressed with the crank condition,but their recommendation really pisses me off. WOW THIS IS A OLD THREAD!

 

[bigred455]

Scratches are 99.99 percent caused by dirty air filter. Even if u change daily!

Assuming no widening of your intake ports or removal of top ports....


Clean that Airfilter and give it a PIG bath in pj1 or premix oil!!!


hope this helps

mike

Thanks Mike ,but that is not the case.

 

[bigred455]

I have the same marks on my '03 kx 250 cylinder. Mine aren't as pronounced as yours seems to be but I have only about 80 hours on this cylinder. I'm guessing it's a flaw in the design that causes these lines on the piston and cylinder. I agree that the massive intake port leaves only two thin bridges to bare the load. Perhaps these are hot spots due to the design. I'm going with a Wiseco piston this time to see if it wears less...I just hope my cylinder doesn't wear more!

T.J. :ohmy:

TJ what ratio are you running

 

[flyinfish]

50:1 Maybe your on to something!

I've run it at 50:1 with Redline for 95% of its life. Maybe your on to something with the ratio. I've noticed on the cylinder the marks are not noticable to the touch and you can still see the original hone pattern over the top of them. Therefore I don't buy the dirt or plate flaking theories, no offense guys. It just doesn't appear to be a mechanical breakdown situation. If it were I would expect more wear on the cylinder. My hone pattern was so good I just deglazed the cylinder with a scotch brite and threw it back together confident that the rings would have no trouble seating and there would be plenty of surface area for the oil to cling to. It seems like hot spots are occuring between the piston and cylinder at the intake bridges. Since the piston is softer than the cylinder it begins to breakdown first because of the extreme localized temperatures associated with the hot spots. the marks on the cylinder appear to be discoloration in the metal from uneven heating. (Perhaps from insufficient lubrication). I do believe that if I ran that piston another 80 hours then the hot spots may have eventually caused some physical break down of the cylinder wall, but I think this would be secondary to the real issue. If we had a million dollars and a lot of time on our hand maybe we could do a real study...wouldn't that be cool. I'd have to do all the test riding of course and you guys could be my mechanics! LOL :laugh:

P.S. I could be way off base. I don't have a PhD. in Rocket Science or Motorcycle Repair so I welcome and thank you for any input...just stop stating it like there's no other possible explanation. :bang: :eek: