Porting Nikasil

[davidblythe]

After hearing horror stories of nikasil chipping when widening the exhaust port and that it is best to do it, prior to a replate, havent attempted this date

always used diamond files to chamfer nikasil and never had an issue

stripped my TS1 down for new bearings and it showed very minimal wear on the bore and piston but really wanted to tune it a bit

It is taking longer than i had hoped for a barrel to come back from a tuner so decided to go for it on this barrel with a pencil die and the little brown barrel grinders instead of a carbide burr

very easy to do, now at a loss to understand why these horror stories exist about nikasil

[sean brady scooters]

such a lot depends on who is doing it dave....
and how they do it.
the trick is to always have the cutter, cutting down if you know what i mean.
from the nicosil into the alloy ,instead of angling it the other way and cutting up from the ally ,which can chip and flake the coating off.

[tony]

You can still chip it with the smaller 3mm burrs.. there are ways and means of doing it. But if ya doing a major port job i get em stripped first.. its so much easier.

[jonny snatchsniffer]

after my fuckup using cutters the sanding wheels that go in the dremmel are good

[oldbiker]

after my fuckup using cutters the sanding wheels that go in the dremmel are good

try to use green grit stones (silicone carbide) it`s softer and will not clog up with the aluminium. If you wont to try a lubricant while grinding wd40 is quite good

[Special X]

The brown sanding drums from dremel work perfectly at about 3/4 speed, done loads with no damage.

[Avantone]

I'd personally be worried about the integrety of the coating after porting even if you avoid chipping it in the process - the coating needs to wrap around the port edge IMO.

Clicky

Nikasil - the common mistakes

Many bike owners and even bike shops take to ports with a grinder in an attempt to scavenge horsepower from their stock cylinders. Porting is carried out almost everywhere the wrong way - in a way that leads to a stuffed cylinder. In stock form and after Electrosil have recoated a cylinder, the Nikasil coating is "keyed in", or wrapped around the port edges, to give the rings a perfect seal as they travel up and down. Most porting cuts the coating around these edges where the bore feeds into the ports. This breaks the critical Nikasil coating around the port edges, and will always lead to flaking of the Nikasil. It won't take long before the cylinder has to be recoated. The lesson is that porting should only be done if the cylinder is going to be recoated immediately.

[Dazza]

I wonder if that's what could be happing to the Rb's? A bit of cleaning up of the ports after plating causing a weakness in the edge of the nikasil which would obviously increase down the barrel as miles were increased?
Just a thought

[J1MS]

Only had one chip when being ported. That was on the bridge between the transfer feeds into the barrel on a TS 1 225, using a brand new tungsten cutter without chipbreakers and it was a single cut tungsten not cross cut.
I usually cut into the edge of the nikosil with a diamond burr or fine grade grit burr. Once the edge is cut through, so long as the speed of the cutter is correct a Tungsten is fine, then finish with fine green grit cutters and polish the port and edges with fine mini flap wheels. I agree with previous posts the piston rings can catch on the ports and lift the nikosil but not Normally if the port edges are cleaned up well and a very light radius polished in with the flap wheel befor finishing with a cloth polishing wheel or felt buffing pad and fine compound.

But I would prefer to port a barrel then have it replated to give a better finish to the port edges.

[Avantone]

I agree with previous posts the piston rings can catch on the ports and lift the nikosil but not Normally if the port edges are cleaned up well and a very light radius polished in with the flap wheel befor finishing with a cloth polishing wheel or felt buffing pad and fine compound.

But I would prefer to port a barrel then have it replated to give a better finish to the port edges.

Thing is, the coating is so thin that you'd be chamfering the Aluminium rather than the Nikasil on the port edges meaning the rings would bulge into the port and be eased back into the bore by the Ali (and then run across the Nikasil edge).

These re-coaters seem to go to huge lengths to mask off areas to save coating unnecessary areas but always coat around the edges and into the ports - there must be a good reason.

I wonder if that's what could be happing to the Rb's? A bit of cleaning up of the ports after plating causing a weakness in the edge of the nikasil which would obviously increase down the barrel as miles were increased?
Just a thought

I thought it interesting that a Kawasaki race team were having brand new factory cylinders stripped and relined to ensure they were getting a thick, consistent coating - I wonder how thick the coatings are on RB's, and as you say, I think I'd keep clear of the exhaust port on an RB with cutters unless you were planning a re-coat.