Nikel bores

Post by **polo2k** » Tue Jul 22, 2008 3:35 am

Hi all.
I was chatting to a friend who recently changed a piston on his old TZR125, when he did it first he fitted a Nikel coated bore. When he did it this time its becasue the bike chewed a ring up, headbutted it with the crown of the piston a few times and then fired it through the piston into the crank case.
The bore survived in perfect condition!
could this be appiled to a minor?

Post by **paulhumphries** » Tue Jul 22, 2008 10:08 am

A mate had the barrel on a bike cylinder recoated so I cann't see any reason why it cann't be done at any engine.
My opinion, however, is not worth doing on a low stressed engine such as the A Series that doesn't rev to over 10,000 rpm like a highly tuned motorbike unit.

Paul Humphries

Post by **bmcecosse** » Tue Jul 22, 2008 3:55 pm

Probably a pressed in cylinder liner - in an alloy block ? No point in an A series - the bores can do 100k if treated right!

Post by **paulhumphries** » Tue Jul 22, 2008 4:23 pm

bmcecosse wrote:Probably a pressed in cylinder liner - in an alloy block ?

It's not uncommon with motorbikes in that you cann't just rebore due to the coating so there are companies who specialise in refinishing.

A very quick search finds this -
http://kustom-kraft.com/NEWNIKASIL.html

Paul Humphries

Post by **chrisd87** » Tue Jul 22, 2008 5:48 pm

No need on a Minor engine. The Nikasil coating is only used on bike engines (typically highly-tuned 2 strokes) to allow them to develop a lot of power for their size by having very exact tolerances (otherwise the engine would heat sieze too easily). Not something that's a problem on an A-Series, although I think some car engines use it to reduce friction and increase fuel efficiency.

Stan Stephens (very well known 2-stroke engine tuner) charges £90 per bore IIRC for re-plating so it's also pretty expensive.

Post by **minor_hickup** » Tue Jul 22, 2008 8:08 pm

Nikasil has been used on production car engines made by Jag (the AJ-V8 ) and BMW (one of the V12s) and it ended up in the nikasil bore lining breaking down with high sulphur content fuels.

Post by **bmcecosse** » Tue Jul 22, 2008 8:10 pm

Ahh yes - I remember reading about that fiasco!

Post by **minor_hickup** » Tue Jul 22, 2008 8:18 pm

If its been used succesfully in bikes I wonder if its the slower running and sulphur content that affects it? Apparently it needs specialist tools to hone as well.

Post by **MGFmad** » Tue Jul 22, 2008 11:33 pm

The Ford Puma 1.7 engine also had the Nikasil coating to the bores, there were a few problems with this engine as well - the coating breaking down and causing high oil consumption.

Post by **youngun** » Wed Jul 23, 2008 10:16 pm

Some old lister stationary Diesel engines had chrome plated bores.
My friends old suzuki motorcrosser also had a nikasil bore, caused nothing but expensive problems!