Cmarti, no worries about the oil going bad. Maybe you should consider the next bigger bottle, as it sounds like you would use it in a timely manner.
We tell our customers that after you get some fresh gas mixed up, you have about 90 days to use it before the gas starts to break down. You see, it's the gas that breaks down, not the oil.
Some dealers will offer a discount if you buy a case of oil, you might ask about that. If you were closer, I'd make you a good deal on whatever size bottles you wanted :)
Poulan Synthetic 2 Cycle Oil
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Originally Posted By: hate2work
When I was at the Mahle plant I asked specifically about this very thing. I had noticed that the saws that were lined with Nikasil could not be honed after being scored, whereas the hard chromed cylinders were almost always able to be honed back to pure chrome.
They pretty much told us that Nikasil was an inferior process/product compared to chrome. That's pretty much reflected in the price of the saws with/without chrome cylinders. Stihl's 4.4 HP Nikasil saw sells for $490, and there 4.4 HP chrome lined saw sells for $609.
Well, you've got manufacturers looking for a less expensive product/process to improve profitability. Note the diff prices of the two units I mentioned. I'm betting Nikasil is cheaper to manufacture.
Additionally, and maybe more importantly, you've got big environmental concerns. The chroming process is a very environmentally unfriendly act. I'm guessing that's not the case with Nikasil. For example, Stihl purposely built their chain making plant in Switzerland to avoid any problems with the German govt about air pollution. You see, all Stihl chain is chrome lined on the top and side plates of the cutters. ( BTW, the same is true about casting magnesium parts, the process puts quite a bit of air pollution out. That's one of the biggest reasons for the major switch to plastics.)
All the Stihl professional units come with a chromed cylinder, and in my experience that means a more durable product. You're right when you said when nikasil is scored it can't be honed clean, but I've honed literally hundreds of chrome lined cylinders back to new again.
Nikasil is harder? Not sure about that one. I can tell you that chrome "feels" harder using the very unscientific method of scraping the cyl wall with a dental pick lol And if nikasil was harder why does it score through to the aluminum on the cyl wall?
Thinner? I can tell you that Mahle told me that chrome is 7/10,000's of an inch thick. I have not heard anything about the thickness of nikasil.
I've never heard anyone talk about oil retention properties. I suspect it's a non-issue with 2 strokes, as there is a constant bath of gas/oil to the engine.
Originally Posted By: hate2work
Cmarti, no worries about the oil going bad. Maybe you should consider the next bigger bottle, as it sounds like you would use it in a timely manner.
We tell our customers that after you get some fresh gas mixed up, you have about 90 days to use it before the gas starts to break down. You see, it's the gas that breaks down, not the oil.
Some dealers will offer a discount if you buy a case of oil, you might ask about that. If you were closer, I'd make you a good deal on whatever size bottles you wanted :)
Originally Posted By: hate2work
Well, you've got manufacturers looking for a less expensive product/process to improve profitability. Note the diff prices of the two units I mentioned. I'm betting Nikasil is cheaper to manufacture.
Oh, and the thickness of either finish can be tailor made, it generally depends on how long the cylinder is left in the bath with the current running for how much material is deposited on the wall.
Bit of an advertorial, but a good article none the less for those who are unfamiliar with the process of coating an aluminium or magnesium cylinder wall.
http://www.electrosil.com.au/news1.htm
I started to write up something, but I'll pinch this straight out of Bell's two stroke tuners book.
Although written twenty years ago it gives some good info.
As time passes, more racing engines are using barrels without any type of cylinder
sleeve. Some people have suggested that factories are doing this to make their bikes
lighter, since an iron sleeve weighs a kilogram or more. Actually, the real reason is
associated with heat transfer.
Initially, manufacturers pressed the iron sleeve into the barrel, but the minute gap
existing between the two formed an insulating barrier which seriously limited heat
transfer to the cylinder's cooling fins. This reduced the power potential of all twostroke
engines.
Later, the aluminium cylinder was cast around the iron sleeve and bonded to it.
This resulted in improved heat transfer and a corresponding increase in performance.
However, no matter how effectively the two materials are bonded, there is always less
than perfect heat conduction from the cast iron sleeve to the barrel.
The next development involved the total elimination of the iron sleeve. Because
the piston rings would quickly wear and score a plain aluminium cylinder, the bore is
plated with porous hard chrome by a special process. The chrome plating is usually
0.08-0.1mm thick and offers a reasonably long service life in racing engines. At times
the chrome has been known to flake, and it is easily damaged by dirt inducted into the
motor. Yamaha have been using chromed bores on their TZ range of motors for some
time now, and Honda went the chrome cylinder route when they introduced their new
CR250R motocrosser in 1978.
The German Mahle firm has been working with a superior electro-chemical plating
called Nikasil. This plating was originally developed for Mercedes when they were
building experimental Wankel rotary engines. Then Porsche began using Nikasil plated
cylinders in the 630hp air cooled 917 model Le Mans racer. This engine later produced
HOOhp in turbocharged form for the Can-Am series. Today, Nikasil cylinders are in
use on tens of thousands of chain saws and other industrial two-strokes throughout
Europe. It has proved to be very successful in racing two-strokes' engines also; the
Morbidelli 125 and Rotax 125 and 250 production racer engines all exhibit excellent low
wear characteristics for the cylinder, piston and piston ring.
The Nikasil coating is a nickel and silicon carbide matrix about 0.07mm thick. The
nickel matrix is very hard, but it is comparatively ductile, whereas chrome is brittle.
Dispersed through the nickel are particles of silicon carbide less than 4 microns in size.
These extremely hard particles make up about 4% of the coating and form a multitude
of adhesion spots on which oil can collect. So beside providing a very long wearing
surface for the piston and rings to bear against, the silicon carbide particles also
contribute to long engine life by ensuring good cylinder lubrication.
The latest advance in cylinder 'plating' was revealed to us at the release of the
Kawasaki KX125 and 250 motocross bikes. Their patented electrofusion process
involves the exploding of wire inside the cylinder in order to plate the bore. After a
hone, the coating is about 0.065mm thick. Fifteen separate explosions plate the
cylinder, first with three layers of pure molybdenum, followed by six alternate coatings
of high carbon steel and molybdenum and then six layers of high carbon steel. When
the cylinder is honed, the last three coats are removed.
The two types of wire are exploded in the centre of the cylinder by a 15,000 volt
burst of electricity, which gasifies the wire. The gas expands out to the cylinder wall,
burning up any oxygen in its path. This eliminates any risk of oxidation and ensures a
good bond between the cylinder and the plating.
Interesting stuff, for sure.
Stihl used to have 4 different sizes of any particular cylinder and piston. They were lettered A, B, C and D. When replacing a piston for a C cylinder, you had to make sure you ordered a C piston, etc. The reason was that the chroming process at the time wasn't exact, so they would measure each cylinder after the process and label it with a letter, then match it with a similar sized piston. Since the chroming process has improved, they only provide one size of replacement piston these days and no longer letter the cylinders.
Where did you get the idea that all saw chain was chromed? There is unchromed chain still in use today for fitment on the very cheapest saws made, usually electric saws. And of course there is carbide chain, Lemery chain as well as diamond chain, all of which are not chromed.
I know the piston skirt retains oil, that's why they have horizontal etchings on them. And since the chrome on the cyl wall is somewhat porous, it would prolly retain some as well.
Did you know that Stihl had a brief experiment with chromed pistons? It didn't last long, and I don't think I ever saw one.
Off topic...
A few years ago at one of the service schools they had made a really interesting teaching tool. They had drilled a hole in the top of a cylinder on a working chain saw and inserted an extremely high speed camera. Then they were able to start the saw and show the combustion bloom in extreme slow motion, and how different fuels effected it. I guess you had to be there, but it was fascinating to everyone who saw it.
OK, you got me on the chain/chrome thing.
I should have stated professional chain for clean/semi-clean wood 
I think one of the Japanese saws (Echo ?) used chrome pistons at one stage, and both Shinny and Echo still use chrome bores. (and were merging as of six months ago)
The combustion thing would have been fascinating.
Way back in the mists of time, my kart engine builder would regularly lift heads to check the ash/burn pattern on the piston crown.
It'd be nice to see it in real time.
I think one of the Japanese saws (Echo ?) used chrome pistons at one stage, and both Shinny and Echo still use chrome bores. (and were merging as of six months ago)
The combustion thing would have been fascinating.
Way back in the mists of time, my kart engine builder would regularly lift heads to check the ash/burn pattern on the piston crown.
It'd be nice to see it in real time.Beeing a snowmobiler i get an seizure now and then.
And Nicasil is the normal cylinder liner. One thing
ive noticed is that a siezure normally doesent hurt the cylinder,
just do a careful cleaning (weak acid and some scrubbing) of the piston remains in the bore and its good to go, whereas a iron or chrome liner definately requiers a good hone (chrome liners is usually=new cyl)
A Nicasil cyl is rebuildable but requiers sending the cyl to some onewho can replate it.
Originally Posted By: ac_tc
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