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pablo83

Are all the WR's/YZ's nikasil lined?

12 posts in this topic

Do all the four stroke WR's and YZ's (400, 426, 450cc) has nikasil linings, or is there a model with a steel liner?

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I assume this means you cant just get the cylinder rebored and slap a new piston in, have to buy a whole new cylinder jug?

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I assume this means you cant just get the cylinder rebored and slap a new piston in, have to buy a whole new cylinder jug?

that's a good question. I assumed you could get oversized rings to compensate for cylinder wear, but yamaha only shows one set of rings on their microfiche. Does anyone know if there are oversized rings available?

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I dont really know, but I have always assumed oversized rings are a thing of the past, I have heard people talk about them but have never seen them.

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Yamaha only allows .0005 inches of wear, that's 1/2 of a thousandth. You cannot hone a cylinder that little easily, and if you can you could probably get away with stock rings anyway.(I work at a machine shop). If you have any wear in the cylinder it has to be recoated or sleeved. You can also just replace it. There is just no tolerance for oversize on these motors. My guess is because of the short skirt on the piston. Good luck, and if you have any rebuild questions, give me a shout.

Dave

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Yamaha only allows .0005 inches of wear, that's 1/2 of a thousandth. You cannot hone a cylinder that little easily, and if you can you could probably get away with stock rings anyway.(I work at a machine shop). If you have any wear in the cylinder it has to be recoated or sleeved. You can also just replace it. There is just no tolerance for oversize on these motors. My guess is because of the short skirt on the piston. Good luck, and if you have any rebuild questions, give me a shout.

Dave

what's the thickness of the nikasil coating?

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My WR426F has a cast iron bore. The p/o installed it for some reason. I guess he wanted to be able to bore it. I think it is a better idea to either buy a new cylinder for $180 or have a used one replated by us chrome.

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what's the thickness of the nikasil coating?

It depends on the manufacturer, the OEM coating is very thin, .002 at the max, usually less. If you go with aftermarket platers you can get it coated a little thicker. When I get a cylinder coated , I get it back unsized at full thickness, and then hone it to size myself. I have a diamond hone at my disposal however.

I just did a topend to my 08 YZ, and was surprised that the barrel is already at the big end of tolerance for the cylinder. I will probably get that cylinder replated,depending on how much a new cylinder. An iron sleeve would be my last option,in fact I would not put one in my own motor.

Dave

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OEM only supports stock bore. Places like M/T (Millenieum Tech), in conjunction with many of the various piston manufacturers can bore a alloy/nikasil barrel to be oversized quite a bit (every heard of a big bore, ie, 290?). After boring, the barrel is re-plated, diamond honed to a exact size.

BTW, the plating by M/T is better quality than oem and therefore lasts longer.

Iron sleeves are a bad thing due to the different rates of thermal expansion. Additionally, they wear whereas a nikasil does not.

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Thanks for the info. What does sending the cylinder out to be plated usually run?

If I remember correctly about 150.00 dollars and up , like William said, if you want to go big bore, then that would be the time, have the plating company bore it to your oversize, and replate it. US Chrome, Max Power, and Millenium are a couple companies that replate.

Dave

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