New rings in a Nickasil type cylinder

[Shaun P]

Was just wondering if anyone has had experience or knows the correct procedure for putting in new rings to pistons in a nickasil type cylinder - eg do you have to rehone and how is that accomplished?

Thanks

[Pussy]

Yep, is best to re-hone... not sure of the procedure

[malcy25]

Put them in and run it. That's what I do regularly on the number of bikes I have with that cyclinder set up.

You can't/wouldn't hone a Nikasil cylinder unless you have a diamond hone and really know your stuff. Remember that Nikasil is only a very thin surface coating and you have no oversizes, as it cannot be just bored to the next size.

Nikasil is very hard but can be damaged if treated wrong. It won't hone up like a cast iron cylinder and the final sizing and surface finish of a Nikasil cylinder is usually done via the diamond hone set up mentioned above.

[cowpoos]

Was just wondering if anyone has had experience or knows the correct procedure for putting in new rings to pistons in a nickasil type cylinder - eg do you have to rehone and how is that accomplished?

Thanks

don't re hone...just chuck them straight in!!

[Sketchy_Racer]

I have very little experience with 4 stroke engines, but myself and most two stroke engine builders I know will hone even a nicasil bore before putting a new piston kit, or new rings in.
The theory behind it is that after many miles of operation, the bores will wear to almost a polished surface, which means there is no where for oil residue to sit while the piston ring is scraping along the barrel. If there is no oil on the direct contact point and especially with new rings which don't match the bore and are point loading, the rings will micro weld to the barrel, and while not entirely wrecking the rings they will not perform at maximum. Also, oil is a major contributer to the sealing of the rings so a lack of it will mean that excessive blow by may occur.
What honing the bore does is creates very small v shaped valleys for the oil to be stored so that as the piston ring slides along, there is enough surface to create a sealing contact area, but also sufficient lubrication.
For running in rings a couple of heat cycles at low engine loading (less loading on the rings means less likely to micro weld) followed by a few short runs, alternating engine speed frequently and no huge loading.

A normal 220 grit stone will be sufficient for the job, but a diamond hone would be desirable.

Take from that as you will, but I am no expert.

Cheers,

-Glen

[imdying]

Oh yeah, you should definitely hone that 2 thou thick plating on your bores

[Bren_chch]

@imdying

never hone plated bores! unless u got loas of money and want to get it replated!

[_STAIN_]

I tend to carefully 800 wet sand the bore to remove any contaminants or varnish, carefully with finger radius sand the port edges, checking there is no chipping or sharp edges.

[Sketchy_Racer]

Oh yeah, you should definitely hone that 2 thou thick plating on your bores

I think you will find you can hone your plating all day long and you won't wear through it.

@imdying

never hone plated bores! unless u got loas of money and want to get it replated!

As above, I don't know exactly where on the rockwell hardness scale nicasil is as I have not tested it, but I do know that it is much harder and much tougher than hard chrome which as a hardness of around RC 70-75 depending on application, which also, you wouldn't hone through in a day if you tried.

If it was so easy to wear through, a piston rubbing along it with the grit of combustion would wear through it less than a thousand KMs, not over 50,000kms.

[Bren_chch]

thanks for that explination... but I wont be trying it any time soon, i couldnt afford a replate just incase someone is wrong

just use scotch bright pad and wd40/crc to deglaze the bore... and thats also also what some of the top plating companies recommend.

[Reckless]

I think you will find you can hone your plating all day long and you won't wear through it.

As above, I don't know exactly where on the rockwell hardness scale nicasil is as I have not tested it, but I do know that it is much harder and much tougher than hard chrome which as a hardness of around RC 70-75 depending on application, which also, you wouldn't hone through in a day if you tried.

If it was so easy to wear through, a piston rubbing along it with the grit of combustion would wear through it less than a thousand KMs, not over 50,000kms.

I disagree sketcy! I'd never hone a Nikasil cylinder!
Personally I don't see the point in puting a few million k's worth of wear in the nikasil even if you use the correct diamond hone? And ring seal/compression has never been a problem as long as you don't premix your fuel to lean.
My 2c only as I say up to you!

There is some very interesting reading in this thread http://www.kiwibiker.co.nz/forums/sh...t=26429&page=2 in the off road forum, read chamchains experience with honing, but opinions both ways, you guys make up your own minds!

[Sketchy_Racer]

I disagree sketcy! I'd never hone a Nikasil cylinder!
Personally I don't see the point in puting a few million k's worth of wear in the nikasil even if you use the correct diamond hone? And ring seal/compression has never been a problem as long as you don't premix your fuel to lean.
My 2c only as I say up to you!

There is some very interesting reading in this thread http://www.kiwibiker.co.nz/forums/sh...t=26429&page=2 in the off road forum, read chamchains experience with honing, but opinions both ways, you guys make up your own minds!

Your right, there are many way to see this. I just use my personal experience coupled with what I have read to decide how I will do things, take a look on google and type in "Honing Nickasil" There are many different ways of skinning the cat, but so long as you remove the glaze, you will bed your rings in properly.

[Shaun P]

Cool thanks for the answers, I thought something along the lines of deglazing should be sufficient.