Skimming a Nikasil lined barrel...

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Fast Eddie

Fast Eddie

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Folks,

Is it possible to have a Nikasil lined alloy barrel skimmed ?

Or does it damage / weaken the Nikasil plating ?
 
FE,
Can't see that it would be that successful even if the layer is thick enough. I would imagine it is blooming hard stuff, but for something like this I would go to Perfect Bore and get their opinion. Someone in the UK used to do gun barrels that had a coating but I can't remember what the lining was, and as you can imagine companies that do that sort of business don't advertise. I knew it saved a heap load of maintenance on the barrels though.
 
Just for clarity folks, I’m asking about the skimming of the head gasket face. The bores are new and shall remain untouched.
 
Fast Eddie said:
Folks,

Is it possible to have a Nikasil lined alloy barrel skimmed ?

Or does it damage / weaken the Nikasil plating ?
Click to expand...

I imagine this question would/ could be answered on a Yamaha Tz 250/350 / 500/700/750 website.
 
Fast Eddie said:
Folks,

Is it possible to have a Nikasil lined alloy barrel skimmed ?

Or does it damage / weaken the Nikasil plating ?
Click to expand...
Nigel
When building our Moto Guzzi 750 race bike a couple of years ago,we used different rods/ pistons to std .In doing this we then had to shorten the Giladoni barrels,(the top fins on either side are now cardboard thick !).We had massive amount taken off more than just skim,this then created more problems with pushrod length,stds etc,but it worked in the end.
But to answer the question- yes this was done easily and caused no damage to the barrels or the nikasil coating,just make sure your man knows what he is doing and has fresh tips on the milling cutters !
Brett
 
Thanks Brett.

(it’s a Giladoni barrel I have, but for a Triumph, don’t mention the none Commando content though)
 
Since the rings never touch the top of the bore, I can't see any issue as long as the top edges of the bores are cleaned up.
 
I’m not worried about that aspect Danno, more about potential chipping or cracking or separation of the Nikasil from the alloy that could then lead to flaking and failure over time.

But it seems this can be avoided as suggested by Brett.

It seems my engineering man is currently doing the stay at home thing that is so in vogue right now, so I’ll have to wait a bit before he can look at it for me.
 
Why are you skimming the barrels Nigel? I can only assume it's to up the compression, never heard of one of the Gilardoni barrels warping across the gasket face? Great piece of kit, just be careful not to over torque the cylinder head as threads are weak unless the later UNF ones, as you probably know! I ask as have these on my T140 for last 20 odd years but std compression is a bit low with the Asso pistons. Apologies for perpetuating non commando content!
 
I have the later UNC threads, so all good there.

The pistons I have with this kit are the low comp ones. I’ve read different claims of 7.4 and 7.9 to 1 CR for these. I do not like these pistons, they’re a botch job IMHO...

With the T140E there is a nice angled squish band machined into the combustion chamber and the stock 8.6:1 pistons have a matching angle. The low comp pistons do not, they totally waste the potential squish.

However, even with 8.6:1 pistons, in my experience, the squish gap is usually way too much (probably due to tolerances in Meriden at the time).

My plan is to use some new, standard sized 8.6:1 pistons with the rings off of the low comp pistons (for the Nikasil bore) and set up the squish somewhere between .030”-.040”. This will give a good functional squish and somewhere around 9:1 CR I reckon.

To achieve this, I expect to have to skim the barrel.

Well you did ask...
 
I would have thought grinding would be better than cutting, but the aluminium is soft.
 
You might try the Pelican Parts BBS for the Porsche 911 and perform a search there. This is a very common topic there and generally the cylinders are handed to EBS or similar to handle this.
 
Fast Eddie said:
I have the later UNC threads, so all good there.

The pistons I have with this kit are the low comp ones. I’ve read different claims of 7.4 and 7.9 to 1 CR for these. I do not like these pistons, they’re a botch job IMHO...

With the T140E there is a nice angled squish band machined into the combustion chamber and the stock 8.6:1 pistons have a matching angle. The low comp pistons do not, they totally waste the potential squish.

However, even with 8.6:1 pistons, in my experience, the squish gap is usually way too much (probably due to tolerances in Meriden at the time).

My plan is to use some new, standard sized 8.6:1 pistons with the rings off of the low comp pistons (for the Nikasil bore) and set up the squish somewhere between .030”-.040”. This will give a good functional squish and somewhere around 9:1 CR I reckon.

To achieve this, I expect to have to skim the barrel.

Well you did ask...
Click to expand...
I've got a 9" angle grinder not doing a lot at the moment
You are welcome to borrow it!!???
 
Fast Eddie said:
Just for clarity folks, I’m asking about the skimming of the head gasket face. The bores are new and shall remain untouched.
Click to expand...

You may seek advice in the BMW community. The airhead bikes from /5 upwards all had hard plated bores AFAIK.

-Knut
 
It's a pain in the ass. We had at my old job a CBN Cubic Boron Nitride wheel for the surface grinder. Others wouldn't cut it. I only ground a couple when cylinders came back from plating and they hadn't done it. Diesel in a spray bottle to keep aluminum from picking up on wheel. Shoot it right where the stone meets part. I tried to mill one once, it destroyed inserts and flaked nicasil
 
I've machined Nikasil type BMW & Honda two stroke cylinders with no problems, but in the lathe. Doing it this way means you can start machining from the bore outwards using a DCMT tip cocked over at about ten degrees to gradually cut the Nikasil so as not to chip it. This isn't practical with a Triumph barrel, so the best way would be to have it ground on a head refacing machine. Basically a Lumsden grinder with a reciprocating table. Most engine shops should be able to do this.
 
Thanks Martyn, I’ll ask around locally for a suitably equipped shop and see what they say. I have to be 100% confident that they are 100% confident though!

Another option I am considering is to have the base gasket flange milled.
 
Fast Eddie said:
Thanks Martyn, I’ll ask around locally for a suitably equipped shop and see what they say. I have to be 100% confident that they are 100% confident though!

Another option I am considering is to have the base gasket flange milled.
Click to expand...
I’ve been watching this thread with interest as I’ve been considering something similar. I got out my gilardoni piston set today and measured the rings. I had read that they are metric and T140 pistons are imperial. This appears to be correct and the gilardoni rings won’t fit standard T140 pistons.
Are there ring sets which fit the 8.6:1 pistons and are compatible with played bores?
 
vsb said:
I’ve been watching this thread with interest as I’ve been considering something similar. I got out my gilardoni piston set today and measured the rings. I had read that they are metric and T140 pistons are imperial. This appears to be correct and the gilardoni rings won’t fit standard T140 pistons.
Are there ring sets which fit the 8.6:1 pistons and are compatible with played bores?
Click to expand...

Indeed, it seems you are correct.
It also seems the Gilardoni kit pistons are very slightly smaller than the standard pistons I have. Easily ‘hone-able’ with an iron block, but a bit of a none starter with the Gilardoni.

So all in all, my piston swap idea is dead!
 
Fast Eddie said:
Indeed, it seems you are correct.
It also seems the Gilardoni kit pistons are very slightly smaller than the standard pistons I have. Easily ‘hone-able’ with an iron block, but a bit of a none starter with the Gilardoni.

So all in all, my piston swap idea is dead!
Click to expand...
That’s a shame- I was hoping you were about to come up with a solution. Do any of the MAP pistons fit?
 
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