Looks like no one's keen to sell me a Nikasil recoat, so that seems good. Heard back from Electrosil (Aust) and they didn't think I had anything to worry about.
Told me standard KTM coat approx 6 thou (0.15mm). I think I made a mistake re thickness I mentioned in earlier post (0.07 probably should be 0.007"), will edit. These recoaters will know Nikasil thickness for certain as they'll be accurately measuring after removing old coating, but we were talking KTM orange flavoured so I don't know if this thickness applies to other manufacturers. They were also extremely helpful and happy to give advice.
They suggested I could even get away with a standard size piston if I couldn't find an oversize one which kind of surprised me. Manual only gives piston/bore clearance of 0.055mm. Electrosil suggested upper tolerance of 0.76mm . They also confirmed diamond hone is best but can use other hone to remove glazing but NO cylinder material should be removed. I think this would be hard to avoid so I'll be sticking with the WD40/scotchbrite pad. Slower but safer. If your cylinder measures up good after a clean, maybe a very light scuff up.
I'd downloaded Electrosil's tech data PDF. Not a huge amount of info in it but impressive as it looks like they have some fancy equipment and are able to measure/quantify what they do eg, friction coeffients, thermal expansion etc. Apparently they use a ceramic material in their recipe as well.
I picked up a 'C' piston from shop and putting that in today. Didn't do any dummy spitting over hone, and they took the 'A' piston back. Just glad I'll be rolling again after so much down time.
Probably should also mention for other KTMer peace of mind, while piston searching I spoke to NZ Vertex piston wholesaler (454 Unlimited ChCh) who also happened to be an Ex KTM dealer. Said KTM coating very good and only A and B pistons normally needed. Confirmed there are 2 bore/piston sizes to cover production variations, check for number cast on side of your cyl.
I guess moral of story is the old carpenter adage: Measure twice - cut once.
I was considering starting to do some compression testing, but told leak-down test better. Is the gear for this similar?
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Copy that on the ring end gap Reckless, I was mainly noting that it was a good indication that I'd lost some bore diameter. I agree, can't see the small amount I'm over spec having any real effect on compression.
Re 'X' and 'Z' stuff, I really think starting another thread a good idea as keen to explore more. Some great points being raised and best to avoid going off topic on this Nikasil caper.
Beamish did you decide on a replater for your KX? Hope you get back on this thread with result. Me, I'd be measuring a newly replated cylinder so I knew exactly where I started.
Will start a thread out in engine section asking for ideas re my 'oven bake' engine experiment results, might as well cast the net wide.
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Originally Posted by camchain
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