1989 YZ490

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4/7/2018 9:34 AM
Edited Date/Time: 4/7/2018 9:36 AM

I just picked up a project 89' YZ490. The bike runs and starts, but it seemed a little down on compression (for a 490), so I took the top end off expecting to see a worn out piston/cylinder. The guy I bought it off of said it was on the original bore (yeah right!). Measured it, and its at 1.50mm oversize. Bore measures within specs, but the rings were worn. This time, i'm not going to bore it - I'm just going to throw a new set of piston/rings in. But since I've only got one bore left on this cylinder, my question is:
Has anyone here tried to get there steel liner coated with nikasil so it lasts longer? Pluses and minuses of it?

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4/7/2018 12:56 PM

Something I've looked at a few times and personally the trade off isn't worth it. You can't have the coating stripped in the acid bath, as it's bad for any steel parts and is why you remove them when an aluminium barrel is replated, so you would end up needing to take the barrel out each time it's replated anyway. Also it doesn't stick to steel that well, apparently.

If all you can get are chrome rings then you certainly can't run it. Easy if the dimensions are shared with a nikasil plated bike though as you can just run the rings intended for those bikes. No idea why as I'm not a Tribologist. I guess it would be an issue with stiction.

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4/7/2018 2:29 PM

The trickest is a aluminum liner in place of the steel then nickasil.

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4/8/2018 6:09 AM

Why not put in a new ironsleeve?
I have read that some tuners nicasil the ironsleeve, but i think that is for getting a small power gain and with a 490 power should not be a problem

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4/8/2018 10:00 AM

Rocky739 wrote:

The trickest is a aluminum liner in place of the steel then nickasil.

Where is this aluminum liner available at, and how much $$?

Also, where are steel liners available at for that matter? I don't see one listed by LA Sleeve.

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4/8/2018 12:32 PM
Edited Date/Time: 4/8/2018 12:33 PM

http://www.laystall.co.uk/cyl-products.php

They do Iron, Steel or Aluminium liners. The original will likely be steel if it's chrome plated.

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4/9/2018 8:38 AM

Mr Happy wrote:

http://www.laystall.co.uk/cyl-products.php

They do Iron, Steel or Aluminium liners. The original will likely be steel if it's chrome plated.

Do these liners come with the ports already cut out in them, or is that something you have to worry about afterwards?
I don't see anything listed on their website for a YZ490.

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4/9/2018 9:06 AM

mxrose3 wrote:

Where is this aluminum liner available at, and how much $$?

Also, where are steel liners available at for that matter? I don't see one listed by LA Sleeve.

Call LA Sleeve . They don't list everything very well.

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4/16/2018 12:20 AM

I actually just had my iron bore 1982 ktm 495 plated by Millenium Technologies. I did alot of calling around and talking to different nikasil platers and was assured this can now be done and will be reliable and durable. Too late to turn back now so I hope thats accurate info, it does look like they did a nice job on it....Photo

Photo

Photo

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4/16/2018 9:11 AM

cwoods wrote:

I actually just had my iron bore 1982 ktm 495 plated by Millenium Technologies. I did alot of calling around and talking to different nikasil platers and was assured this can now be done and will be reliable and durable. Too late to turn back now so I hope thats accurate info, it does look like they did a nice job on it....Photo

Photo

Photo

Any pics of the nikasilled steel sleeve?

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4/16/2018 10:04 AM

No I dont.

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4/16/2018 1:38 PM

I would have to look at the receipt but I believe it was right at $300 for the replate. I had a new nos Maule piston set in stock 92.25mm size and the bore of the cylinder was within spec to replate to that size. I contemplated just boring it over and getting a Wiseco someone had a run of made.
I read alot of online opinions on plateing an iron bore and some were that the plating would flake after a while so I got to calling around asking questions on it. Apparently the process has changed in recent years and its common practice now without issues. In more poking around Ive found alot of vintage racers doing this witb there cylinders. If its as durable as Ive been told its a win win in my book to have a plated cylinder in this big bore of mine.

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4/16/2018 2:29 PM

http://www.advancedsleeve.com/index.html
Check out these guys for alu sleeves. Also Millennium, Powerseal or US Chrome or another plating place might know. I still think that would be trickest. better heat transfer and expansion rates.

I talked to a buddy that has done several nicasil on iron cylinders and no issues after several years of racing. He thought the piston and ring wear was greatly reduced. He used Powerseal.

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4/17/2018 7:48 AM
Edited Date/Time: 4/17/2018 7:49 AM

cwoods wrote:

No I dont.

Is the bike together and running? I wouldn't mind knowing if it's OK after the first 5 or 10 hours. If it were to flake off or fail I guess that's a reasonable amount of time to expect it to happen within.

There aren't any stories on the net where people have had it done and it has failed. Maybe that's a good sign and I should try it.

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4/17/2018 10:19 AM

I just went through the motor top and bottom, Im starting on the chassis now so it will start break in a couple weeks from now. I really dont see it flaking... call a couple places....ease your mind. Alot of vintage racers are going this route.

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4/18/2018 12:36 PM

Thanks for everyone's input on this. I'm probably going to opt for the plating on the steel liner on the next re-bore that I do.

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4/24/2018 2:18 AM

mxrose3 wrote:

Thanks for everyone's input on this. I'm probably going to opt for the plating on the steel liner on the next re-bore that I do.

I have a brand new cylinder for your bike if you're interested. smile

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