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Nikasil or sleeve?

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My bike's cylinder was Nikasil coated from the factory.  The coating has worn through and I am considering getting a sleeve inserted instead of having it recoated - seems to be more cost effective.

 

Any thoughts or experience?

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I'm a big cheapskate and I'd get it plated.  It may also detract from the value when it's sold if it's sleeved.  Do it right.

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The thing is, a sleeve costs $90.  It costs another $90 to have it installed and finished.  A replate costs about $200.  You don't have to worry about boring between rebuilds, you don't have to worry about using oversized pistons, it lasts longer, it works better.

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Well I see you have opened that debate.

I opted for a sleeve for a number of reasons but they both have their pros and cons. 

When you sleeve you will need to match port to do a proper job and this is where extra expense can come into play. Sleeves can be re bored and oversized with minimal expense so in the long run they CAN be cost effective IF you are planning on keeping the bike. Sleeves can have a cross hatch easily applied and we do all ours here at our shop so the expense for us is very low.

Nikasil is very good and will not wear or flake providing it has been well maintain and you change the pistons at the suggest intervals or sooner. There is nothing wrong with plating and I believe in the USA it is cheap to plate a cylinder. only about 2 or 300 dollars. To plate here in NZ is about 650.00 so a sleeve was the best option for me. It also depends if you are MX competiton riding or just a weekend warrior or your riding style in general. 

Good luck with your decision. 

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Thanks guys,

 

I think I'll go for the recoat, although it's $299.

 

I was really only looking at the initial cost of doing the job, not future costs down the road.  Since posting this question I have read a few other discussions and it seems like the Nikasil coating offers a few advantages over the sleeve, such as longevity and cooling.

 

I have explored all the options, including getting a big-bore kit to replace my cylinder and have decided to keep it stock and get it coated.

 

Thanks again.

Edited by klx300green

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Well I see you have opened that debate.

Sleeves can be re bored and oversized with minimal expense so in the long run they CAN be cost effective IF you are planning on keeping the bike.

 

Well not a lot of shops are willing to bore and finish such small cylinders.  Even in industrial California about the only outfit boring cylinders under 3 inches is LA Sleeve.  So that means shipping and downtime, too.

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Well not a lot of shops are willing to bore and finish such small cylinders.  Even in industrial California about the only outfit boring cylinders under 3 inches is LA Sleeve.  So that means shipping and downtime, too.

 

That's interesting.........No boring of sleeves under 3 inches. I wonder why that is. What do you think?

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That's interesting.........No boring of sleeves under 3 inches. I wonder why that is. What do you think?

 

Probably low-demand... so they don't have the tooling for smaller bores.

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On top of the fact that a steel or iron sleeve transfers heat less well than an aluminum bore does, all sleeves form a thermal barrier at the joint between the two metals that exceeds the thermal resistance of even the iron.  Even the sleeves that were used in Japanese bikes during the late sixties through the 80's that had the cylinders cast in place over them using a fluxing compound don't carry heat off anything like as well as a Nikasil plated aluminum bore.  That shifts more heat to the head.  Steel sleeves also introduce cold clearance issues relating to the different expansion rates of the aluminum piston and the sleeve, issues that are bypassed by using aluminum bores.

 

And in two strokes, you have the matter of matching the port windows to the new sleeve, which task can be tedious, to say the least.

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On top of the fact that a steel or iron sleeve transfers heat less well than an aluminum bore does, all sleeves form a thermal barrier at the joint between the two metals that exceeds the thermal resistance of even the iron.  Even the sleeves that were used in Japanese bikes during the late sixties through the 80's that had the cylinders cast in place over them using a fluxing compound don't carry heat off anything like as well as a Nikasil plated aluminum bore.  That shifts more heat to the head.  Steel sleeves also introduce cold clearance issues relating to the different expansion rates of the aluminum piston and the sleeve, issues that are bypassed by using aluminum bores.

 

And in two strokes, you have the matter of matching the port windows to the new sleeve, which task can be tedious, to say the least.

Hey Grey Racer..........

That's all good and well for what you are saying and I completely understand and get that, And please forgive me for my ignorance as I don't want you to think that I am questioning what you have said to be untrue or get into a heated debate......... I just would like to understand it a little better. My question is though.............With all that said and done with regards to better heat transfer, dissimilar materials, and mainly heat transfer in general...........What does that really mean. Does it mean that for a forged piston you can have a slightly smaller piston to cylinder clearance, but what are those benefits? For a cast piston the same can be achieved as the thermal expansion rates are the same for barrel and cylinder, and what are those benefits. I understand that installing a sleeve you will want a little more clearance and I also understand about the match porting and needing the engine to warm up a little longer so there is limited risk of cold siezure, but this would depend on the piston installed and the clearance given. Does it mean that a aluminium bore can be run harder or started and run quicker with no warm up..........does it mean that it is only of real benefit to racers and not the weekend warrior? I can see that heat dissipation from the barrel to the head and out to the cooling and radiator will run a cooler engine but I am struggling to see the real pay off here. We have sleeved before and I am yet to be convinced of the heat argument. Please educate me on this.

Thanks Grey.   

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Hey Grey Racer..........

That's all good and well for what you are saying and I completely understand and get that, And please forgive me for my ignorance as I don't want you to think that I am questioning what you have said to be untrue or get into a heated debate......... I just would like to understand it a little better. My question is though.............With all that said and done with regards to better heat transfer, dissimilar materials, and mainly heat transfer in general...........What does that really mean. Does it mean that for a forged piston you can have a slightly smaller piston to cylinder clearance, but what are those benefits? For a cast piston the same can be achieved as the thermal expansion rates are the same for barrel and cylinder, and what are those benefits. I understand that installing a sleeve you will want a little more clearance and I also understand about the match porting and needing the engine to warm up a little longer so there is limited risk of cold siezure, but this would depend on the piston installed and the clearance given. Does it mean that a aluminium bore can be run harder or started and run quicker with no warm up..........does it mean that it is only of real benefit to racers and not the weekend warrior? I can see that heat dissipation from the barrel to the head and out to the cooling and radiator will run a cooler engine but I am struggling to see the real pay off here. We have sleeved before and I am yet to be convinced of the heat argument. Please educate me on this.

Thanks Grey.   

 

Greater piston to cylinder clearance (i.e., using forged pistons) increases piston rocking in the bore, leads to less ring stability, blow-by, noise and eventually more wear over time.

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70 years ago, the problem was that because aluminum expands so much more and so much faster than iron, the piston needed a great deal of cold clearance in order to have the right operating clearance at full normal temperature. That problem was mostly solved by adding a high content of silicon to the aluminum alloy to reduce and control expansion.

 

But until as little as 40 years ago, that left forged pistons with the same problem because the silicon made the aluminum to hard to forge by the methods then in use.  The situation often lead to forged pistons in 3.5-4" bores being fit to as much as .012" cold clearance, and that lead to a variety of difficulties.  If the engine wasn't babied during warm-up, it could damage itself through excessive piston slap, or by "cold seizing", a condition under which the piston clearance is too great to allow heat to be carried off of the piston skirt by the cylinder, allowing the piston to expand rapidly until it seized before it could stabilize thermally in the bore.

 

Modern forging technologies now allow high silicon aluminum alloys to be forged, so that element is finally been reduced to a livable state, but the biggest improvement is the use of the plated aluminum bore, which leaves the piston and cylinder with very similar expansion rates and operating clearances that are nearly constant across the whole temperature range.

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 which leaves the piston and cylinder with very similar expansion rates and operating clearances that are nearly constant across the whole temperature range.

 

the neatest part about the cylinder being aluminum.

 

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Ok, I've been reading up on  lot of tool coatings (Trying to get a nice, almost acid, green coating for some stanchions) and I was wondering how hard anodizing would hold up for a cylinder, and maybe some ti nitride coatings for the rest of the internals? Any thoughts?

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Anodizing is neither hard enough, nor does it stay in place well enough.  Ti nitride I don't know about as far as why it doesn't find use for this application, but it would be extremely difficult for it to displace Nikasil. 

 

I have never seen Nikasil "peel" for one thing.  It can be nicely finished with a hard enough stone, and is off the Rockwell C scale hard at something like 85+.

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Ok, I've been reading up on  lot of tool coatings (Trying to get a nice, almost acid, green coating for some stanchions) and I was wondering how hard anodizing would hold up for a cylinder, and maybe some ti nitride coatings for the rest of the internals? Any thoughts?

 

 

Anodizing is neither hard enough, nor does it stay in place well enough.  Ti nitride I don't know about as far as why it doesn't find use for this application, but it would be extremely difficult for it to displace Nikasil. 

 

I have never seen Nikasil "peel" for one thing.  It can be nicely finished with a hard enough stone, and is off the Rockwell C scale hard at something like 85+.

 

Interesting note here, BMW has started using aluminum blocks with hard anodized cylinders on some of their engines rather than using sleeves or plating. This comes with its own list of challenges though. Hard anodize does not expand and contract with temperature like aluminum does, and its hardness makes it brittle. If temperature gradients are not controlled correctly you can end up with a crack in the coating. It also creates dimensional issues if you have to strip it and re-anodize. Plating like nikasil just builds on the base material, so it can be stripped and replated without dimensional issues. Anodize builds and penetrates into the surface of the aluminum, so if you strip it, the dimension of the bore will not be the same as what you started with.

 

Hard anodize does have its positives though. It has very good wear resistance, it can be impregnated with PTFE (Teflon) to decrease friction, and there is no chance of it flaking since it is not bonded to the surface like plating is.

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