can honing uncover cylinder wall damage not visible to the naked eye or to the touch

[go high fast]

prior to honing and upon both visual inspection and inspecting with fingertips the cylinder appeared to be in good shape and ready for honing. After honing, the cylinder reveals scoring that is both visible and easily detected by touch and now it is recommended that the cylinders be replated. technician did not even proceed any further to measure cylinder to piston clearance and ring end gap which was the sole purpose of leaving cylinders and pistons.

Does this seem likely?

does anybody have any experience with this type of a situation?

it seems strange that they would have proceeded to hone the cylinders in the first place if they felt they were needing to be replated unless he felt honing would solve the problem?

Is it possible the cylinders could have been damaged when measuring piston to cylinder clearance or setting ring end gap? I had also asked that they check for the holes for roundness and straightness.

sled is a 2010 800 RMK. Will have after-hone photos next week. Should have taken pre-hone photos before dropping off cylinders but did not.

 

[Stngllhm]

I can't say for sure on the honing side but I run a lathe at work and on a freshly machined surface cracks show up quite clearly

 

[sledhed]

I can't say for sure on the honing side but I run a lathe at work and on a freshly machined surface cracks show up quite clearly

But that is not relevant on a nikasil coated cylinder in my experience. It is a plating process. There would not be score marks under the surface unlss they honed clear through the nikasil.

I would not have thought of taking pix before taking it in for honing... definitely want to see what it looks like now.

Also when honing nik, it should only be a light hone, enough to break the glaze but no more, so the new rings seat in properly. If they over-honed I would raise holy heck...

 

[xc6rider]

Yes its possible, especially on cylinders like Poo 800's that have issues with breaking cylinders.

1. Plating process could have poor coating contact, not very likely, but possible. Hone goes thru, breaks or removes the affected area. It looked good, but may have a tiny bubbled spot.

2. Most likely scenario. Piston slap in out of round cylinder, weakens underlaying aluminum, weakening the bond between nicasil. Hone again exposes it. Nicasil is much stronger than aluminum, however very thin. It may appear to hold together during damage, only to pop loose all the sudden. Kinda like seeing the chrome from a chrome plated car bumper remain intact over a bent section of steel, during an accident. A little bubbled spot may appear, and little poke may break it loose. This would only multiply over a cracked section.

Honing, atleast when i do it, is a once and done process. I never do a a tiny bit at a time, then inspect the cylinder, and keep going multiple times. It usually takes very little.


Depending on the scoring or nicasil damage that did end up showing, i would maybe try to do a little acid clean, and a little more honing, hoping it might come out, while also knowing that a replate is still very likely.

 

[LoudHandle]

My two cents, thoughts are; they either used the wrong hone (as Nikasil requires a diamond hone) or a dirty one and scratched the he(double hockey sticks) out of a otherwise smooth and re-usable finish. Inadequate or sporadic lubrication while honing can also cause egregious scratches in the surface finish. There needs to be enough lubrication to FLUSH away the material removed, a few sprays of WD-40 ( as I've seen recommended on here) is no wear near enough. The pics will confirm or deny my suspicions.

A lot of shops try and get away with conventional stones or even ball hones for Nikasil, which in my opinion just F's up a perfectly re-usable cylinder and destroys a perfectly good hone. Nikasil is nearly as hard as diamonds to start with, so why would you try and hone it with a normal stone? It will just wear the conventional stone out and not even touch the Nikasil, but yet people try and a lot of drop in kit makers recommend the practice, wrongly.

 

[xc6rider]

My two cents, thoughts are; they either used the wrong hone (as Nikasil requires a diamond hone) or a dirty one and scratched the he(double hockey sticks) out of a otherwise smooth and re-usable finish. Inadequate or sporadic lubrication while honing can also cause egregious scratches in the surface finish. There needs to be enough lubrication to FLUSH away the material removed, a few sprays of WD-40 ( as I've seen recommended on here) is no wear near enough. The pics will confirm or deny my suspicions.

A lot of shops try and get away with conventional stones or even ball hones for Nikasil, which in my opinion just F's up a perfectly re-usable cylinder and destroys a perfectly good hone. Nikasil is nearly as hard as diamonds to start with, so why would you try and hone it with a normal stone? It will just wear the conventional stone out and not even touch the Nikasil, but yet people try and a lot of drop in kit makers recommend the practice, wrongly.

I use nothing but ball hones for deglazing and have had great luck. Old school i guess... Picked up from a very seasoned engine builder in the states. More than one way to skin a potato!

 

[snowmanx]

I use nothing but ball hones for deglazing and have had great luck. Old school i guess... Picked up from a very seasoned engine builder in the states. More than one way to skin a potato!

I agree, I have used ball hone to clean up cylinders, it can take some light streaking away, but it will not create new cross-hatching IMO.

 

[sledhed]

Interesting different takes on this. When I put new pistons into my 860, I followed Carls recommendation, which is conventional hone, just enough passes to give some fresh cross hatch to help new rings break in. Polaris service manual says "cylinder bore must be deglazed whenever new piston rings are installed..." "NOTE: A Nicasil cylinder can be lightly honed with a soft stone hone but can not be oversized."

While I am not sure if I put enough or too much new crosshatching in, or if it was exactly the right angle, but I could see new light markings so I called it good. Cleaned them up, washed them in hot soapy water, dried them, oiled and installed. I also checked ring gap (it was in specs) and called it good and put it back together.

Wanting to see those pictures though. Since it is a 2010 block with 500 or so miles on it since new, it has thicker skirts on the cylinder than the 08-09, and being lower miles I would think it should not be damaged from piston slap yet...

 

[mtncat1]

a ball hone is the worst kind of hone and should never be used on a 2 stroke engine , a cylinder will almost always look good when ball honed because the hone will conform to the cylinder and hide any irregularities, a ridged diamond hone should be used for modern snowmobile cylinders and will reveal hidden damage to the cylinder i.e. low spots cracks and other wear related flaws . unfortunately the shop is probably right in this case.