Cylinder - Replace or reuse?

12 replies to this topic
  • tdamore

Posted November 10, 2008 - 09:41 PM


I am about 2/3 of the way done with my motor rebuild. Tonight I washed the cylinder after having it honed and was about to run a cloth with some ATF on it through the bore when I noticed what appears to be minor scoring on the intake and exhaust sides of the bore. It is just visible to the eye, but not noticeable to the touch except for one small line that I can feel and even that one is not deep enough to catch a fingernail on. I can just sense something when running a finger over it. Does this warrant replacing the cylinder? I can get one for about $200 but if I dont need to I would rather not. I am already WAAY over budget on this rebuild :worthy:

*56k warning - These pics are huge to retain the detail


  • grayracer513

Posted November 10, 2008 - 10:49 PM


Pretty borderline. What did you hone it with?

  • tdamore

Posted November 10, 2008 - 10:54 PM


Pretty borderline. What did you hone it with?

Had it done by the local shop for a 20 bucks. They told me they used a ball hone and ran it through about 4-5 times. Also, I am not sure what those dark lines are in the 3rd and 4th pictures but they are not actually in the cylinder. Ghosting from the flash or something I guess. The 2nd and 5th pictures are probably the best of the lot.

  • crayztwentyseven

Posted November 11, 2008 - 12:27 AM


close, use your own judgement. If you use a new piston and rings then you would probably be fine. I rebilt a yz 400 with a cylinder that had very light scratches just like that about three years ago, it now has over 300hours on it(documented by hour meter) and it has near perfect compression still.

  • grayracer513

Posted November 11, 2008 - 07:02 AM


In an iron or steel bore, I would simply have run the ball hone (which is always the best choice to refinish a cylinder that has not been rebored) through it a few more times. However, with a nikasil plated bore, you would in the first place not be very likely to remove a significant amount of metal, since it's so very hard. Secondly, you wouldn't want to, since the plating is also very thin.

The worry here is that the scratches you see are deep enough to have possibly gone through the plating, which introduces the possibility, though unlikely, that the plating could peel from that point. It is also true that the scratches will transport a small amount of oil past the rings if they are far enough up in the cylinder, but it usually doesn't show up as oil consumption.

I have reassembled a couple of engines that looked like that, and they worked out fine for a long time afterward. Did I worry about them? Yes. For a while.

It's a coin toss. It will probably be OK, though.

  • tdamore

Posted November 11, 2008 - 09:44 AM


Running a new Wiseco 12.5:1 piston and rings. (I thought about going OEM but thats what was in it and I was happy with the power so why change a good thing). I think I may just bite the bullet and get a new one. After all that I have done with this it seems foolish to get cheap now. Thanks for the help :worthy:

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  • yamaha542

Posted November 11, 2008 - 12:24 PM


run your finger nail over the scratch, if you cant feel it "catch" then you are good to run it. My cylinder looks like that and i have had no problems.

  • VB_Racing

Posted November 11, 2008 - 04:28 PM


From my experience , especially if you are using a forged piston, you may want to replace that cylinder. Like Gray says, it is close, I would feel more comfortable reusing it if you were using a stock piston. side wear is very common, and seems to be more common with a forged piston. My 2 cts. If you can feel the scratches with your fingernail, definately replace the cylinder


  • curthall11

Posted November 11, 2008 - 05:31 PM


The cylinder on my 00' 426 was just like that and I put it back together and I have put 25+ hours on it since with no problems at all.

  • yz007f

Posted November 11, 2008 - 05:52 PM


I don't think I would be rushing out and buying a new cylinder. Like what was said already if you can't feel it with your finger nail then I would not worry about it. But I would be putting in a OEM piston back in for sure! When the ball hone was used, it wouldn't really take much off at all. The OEM nikasil is really hard which grey said. Best to use on the cylinders is a ridged hone with nikasil stones and even at that, it would take a ton of passes to take a significant amount out of the cylinder.

I had a 03' with some lines on the intake side and always used OEM pistons. The previous owner I'm guessing would not warm it up long enough. It never gave me any problems at all but these were lines that you could not feel with your finger. Stick with OEM and you will sleep at night!

  • desert-rat660

Posted November 11, 2008 - 05:53 PM


thats how the cylinder looked in my 450, but i had a noticeable ridge at the bottom of my cylinder so i replaced it. otherwise i was going to reuse it

  • gtxkid

Posted November 11, 2008 - 05:59 PM


I think i would run it. does not look bad to me unless you are going to line up with Chad Reed, then i do not think it will matter anyway.
I learned that a magnetic drain plug is a must and oil change every 2 hour is standard on a 2 stroke.

  • tdamore

Posted November 19, 2008 - 11:21 AM


I replaced it. Just not worth the risk considering the time and money I put into this rebuild.

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