Substitute piston/rings for 66cc/80cc China engine (47mm bore)

[Deleted member 12676]

US Chrome says that plain chrome plating (such as the Grubee cylinders has) has a temperature limit of 400 degrees Celsius so a higher cylinder temperature due to advanced ignition at high RPM, overly lean fuel-air mixture, or engine compression over 135psi can be a causative factor with cylinder plating flaking. Here is the info posted at the US Chrome site about the plating they can put on cylinders:

NiCom Nickel Silicon Carbide Dispersion Coating

NiCom is an electro-composite coating consisting of a nickel metal matrix with hard particulate dispersed uniformly within it. The process involves electroplating nickel in the presence of hard particulates, such as SiC, under conditions allowing the hard particulate to co-deposit with the nickel. The result is an electroplated composite material where engineering thickness can be achieved for both original equipment manufacturing (OEM) or overhaul and repair.

Electro-composite materials, such as NiCom, are viable alternatives to Hard Chromium Plating due to their excellent wear resistance. Superior sliding wear characteristics are achieved due to the hard particulates dispersed within the metal matrix. Mating components ride on the hard particles, which can vary from SiC to BN to diamond depending on the wear condition application, resulting in wear 5 to 10 times better than Chrome.

Once the NiCom coating has been applied, it can be diamond honed or ground to finish dimension to meet surface finish requirements. Common applications of NiCom are found in bores of internal combustion engines with uses ranging from weed trimmers to snowmobiles to high performance race cars. Most any cylinder bore/piston application where sliding wear resistance is important is a candidate for NiCom electro-composites.

Features & Benefits
Excellent sliding wear rear resistance usually 2 to 10 times better than chrome
Buildup possible up to 0.030+
Superior adhesion to all metals including aluminum and titanium
Outstanding corrosion resistance

Properties
Frictional properties are very good and the coating has excellent oil retention due to the oleophyllic nature of nickel and silicon carbide. The coefficient of friction can be further enhanced by adding laminar lubricants to the deposit.
Hardness: 500-625 HVN100
Corrosion resistance is outstanding and is superior to electroless nickel and chromium. In the presence of chlorides

 

[HeadSmess]

now thats information

what interests me is how they get the carbides (and nitrides..ie, the B(oron) N(itride)) in the mix whilst plating... mmmmm, tantalum carbide martensite or ferric carbide... (what makes cast iron good. excess of carbon leads to free carbon in the form of graphite, thats soft and slippery, and also chemically combines with some iron and forms a super hard carbide... the whole lot being held in a rigid and strong type of matrix, thats easily machined)

colloidal solutions, and the particles are ultra microscopic and suspended in the solution? gravity, and they just keep rotating the work/ agitate the mix? detergents?

cant see how they could include it if they do vacuum plating, as the metal being applied is gaseous...


so, what we require now is a cheap foundry/machine shop that will pop out a hundred correctly ported cylinders, that are subsequently plated with some hard metal... for the smallest fee possible per piece.

and then we have replacement cylinder combo kits with 1mm rings good for 16k+ oh, and the top of the cylinders are properly faced for good gasket free head fitment with the correct squish band... for, maybe, if you smooth talk the right people...250-300 a pop. how much is the minarelli piston kit worth normally?


think of all the high performance cranks you could sell after the things grenade at 12K!

 

[Deleted member 12676]

substitute piston/rings for 48cc

Both the substitute piston/rings for the 48cc that I list on my site are thick ringed so the 48cc has the advantage here. Also the 48cc is less imbalanced than the 66cc and so vibrates less. Porting them to rev higher can make up for the lack of displacement. Horsepower is directly related to RPM. So 66 divided by 48 is 1.37 which multiplied by 5500 (standard max RPM) is 7560. So a 48cc ported to rev to 7560 RPM can produce as much power as a non-ported 66cc.
The piston I am talking about is the Honda Hobbit piston/rings that sells for $30 and is also 1mm higher for more engine compression without having to buy a high compression head.
The Minarelli piston/rings for the 66cc is also $30.

 

[Fabian]

Horsepower is directly related to RPM. So 66 divided by 48 is 1.37 which multiplied by 5500 (standard max RPM) is 7560. So a 48cc ported to rev to 7560 RPM can produce as much power as a non-ported 66cc.

but it doesn't work out that way in real life, because no one wants to rev the rings out of their engine "all the time", just to make the same power that a 66cc engine does at much more sensible rpm; which also prolongs engine life.

 

[Fabian]

then we have replacement cylinder combo kits with 1mm rings good for 16k+ oh, and the top of the cylinders are properly faced for good gasket free head fitment with the correct squish band... for, maybe, if you smooth talk the right people...250-300 a pop.

I would pay $350 for a big bore version of the 66cc cylinder with a properly cast cylinder and high quality surface treatment on the cylinder bore.

 

[Deleted member 12676]

Fabian, small bore 2 smokes are normally designed for high revs to make up for their small size.
7500 RPM is nothing for a small two stroke. I was reving mine to 8000 before I even balanced my crank. Now it revs to 8500. Some small bore motocrossers rev to 12,000.
Of course if there is vibration that causes a problem with reliability because it loosens nuts. But these engines have a vibration problem even before porting them to rev higher. Using a titanium wrist pin is the very least you should do to try to correct some of the problem.

If you are going to do something then why not do it right. Drilling larger holes in the crank is really essential with these engines if you want reliability. It could be the imbalance is what causes the upper conrod bearing failures. The Jaguar CDI and a lighter wrist pin help a lot but really the crank hole sizing is the root problem.

 

[Fabian]

I find it surprising that i have never had an upper connecting rod bearing fail, in any of my engines.

The upper connecting rod bearing in my current engine has been installed in my two previous engines, one of which traveled 10,000 kilometers before the lower connecting rod bearing failed.

So far, i have had perfect reliability with regards to the stock standard upper connecting rod bearing; to the point where it's been through three engines and still continues runs acceptably well; long after the lower connecting rod bearing has failed.

 

[Deleted member 12676]

Fabian, don't forget that you have the Jaguar CDI which lowers the stress on those bearings

 

[Fabian]

I do agree with you, but even so (in the operation of my various 66cc 2-stroke Chinese bicycle engines), it's always been the lower connecting rod bearing that's failed, and never the upper connecting rod bearing; though many other people experience this situation the other way around.

Why am i experiencing different results to many out there, even on high mileage engines that have had many hours of low speed, high stress heavy haul?

 

[Deleted member 12676]

big difference between you and others is that you haul heavy loads uphill