Is this engine 100cc or "80cc" (66cc)?

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https://www.ebay.com/itm/383920220520 they say its 100cc and a 49mm piston size. A review said its actually 80cc not 100cc. I measured the bore and piston and they're both about 49mm. I sanded the cylinder sleeve (I now realize this was bad). I've no idea if its chrome/nikasil plated or if its solid steel and can take a light sanding but would like to replace it.

1. Is this in fact a 100cc engine or 80cc?

2. Any suggestions on a compatible cylinder replacement on ebay?
 

ImpulseRocket89

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It's neither lol. 49mm bore and a 40mm stroke means it is 75.43cc
The whole "100cc" thing comes from the chinese method of calculating displacement, which is different from the way the Western world does so.

In the description it states it has an iron sleeve cylinder. That means there is no plating.
 
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It's neither lol. 49mm bore and a 40mm stroke means it is 75.43cc
The whole "100cc" thing comes from the chinese method of calculating displacement, which is different from the way the Western world does so.

In the description it states it has an iron sleeve cylinder. That means there is no plating.

Does this mean the sanding did in fact not damage the cylinder then and im good to continue using the cylinder? Or is it trash? What about the tiny pitting / scratches I left from porting?

Also - If its an iron sleeve cylinder is generally just pure iron or does it have additives like chrome to make it stainless steel or any sort of coating?

scratches:
 

ImpulseRocket89

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As for sanding the chrome plating, if you didn't sand through it, it will likely be ok, but not ideal. I usually ball hone my cylinders with a 320 grit ball hone to add some level of cross hatching for oil retention during break in and it has never once caused an issue. The issue I see here is that the sanding looks in line with the direction of piston travel. Ideally, if your goal was to do something similar to a coss hatch, it needs to be closer to perpendicular, and ideally, at a 45 degree angle to the direction of piston travel - in a cross cross pattern.

As far as the chatter marks from the bits you were using. It may be ok, but slowly over time the edges of the rings will catch those spots and start chipping away at the lining. This means the overall life of the cylinder will be reduced as the lining will fail as it runs over time.

The iron sleeve is more or less iron. It may have a few other metals in it, but it is not stainless steel. At best it is a very low carbon steel. VERY low. I have an iron sleeved "110cc" engine, and the iron they used is very soft (as far as iron goes). Most likely a machined cast iron.
 
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Good info - im learning more. You state iron cylinders do not have plating (chrome/nikasil), so does this mean the sanding is no issue then since theres no plating to sand off?

I may reinstall the engine and continue riding. But do you have any suggestions for a "100cc" cylinder replacement? Its difficult finding a compatible cylinder with the different and misleading measurements. Its a 49mm bore, but how do you know its a 40mm stroke? Would a "80cc" (66cc) cylinder work or should I only look for cylinders advertised as "100cc"? Some have you second guessing if they're using the US or Chinese measurement, especially when a lot of info is missing. Im comparing engines on Ebay.
 

ImpulseRocket89

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Good info - im learning more. You state iron cylinders do not have plating (chrome/nikasil), so does this mean the sanding is no issue then since theres no plating to sand off?

I may reinstall the engine and continue riding. But do you have any suggestions for a "100cc" cylinder replacement? Its difficult finding a compatible cylinder with the different and misleading measurements. Its a 49mm bore, but how do you know its a 40mm stroke? Would a "80cc" (66cc) cylinder work or should I only look for cylinders advertised as "100cc"? Some have you second guessing if they're using the US or Chinese measurement, especially when a lot of info is missing. Im comparing engines on Ebay.
Iron cylinders don't need to be plated. The iron sleeve takes the place of the plating.

Basically, the cylinder cannot be aluminum because the aluminum piston and cylinder would rub against one another, and aluminum being soft it would seize up within short order. It has to do with the hardness and coefficient of friction. Iron/steel has a very low coefficient of friction and is much harder than aluminum, so when other metals rub against it they tend to just slide across one another - this is why trains are so efficient they ride steel wheels on steel rails. The reason Chrome, Nickel Silicon Carbide, and ceramic coatings are used in place of iron is for the same reason. The materials are relatively hard compared to aluminum and have extremely low coefficient of frictions - even better than iron.

The big advantage to an iron sleeve comes down to reliability. Cast iron is very porous, so it does an extremely good job at retaining oil which has benefits for longevity. This is why iron engine blocks, and even iron sleeved aluminum engines, were used in car engines.
The other benefit of iron cylinders is that the liner can often be lightly honed and re-used during a rebuild, so as long as no major damage has been done, and it hasn't been worn too far out of round, the cylinder can be re-used during a rebuild.

There are technically downsides to iron sleeves. Iron doesn't conduct heat as well as aluminum, so they do suffer a bit in terms of thermal efficiency. You also need to avoid pushing them hard from a cold start because the iron expands slower than the aluminum around it, so for the first couple of minutes you want to take it easy and not push very hard, otherwise the sleeve can shift/move. It's not common, but a possibility. Another downside is the iron sleeved cylinders are a bit heavier. Not a ton of weight, but its still technically a "negative" aspect.

Looking at the platings, they too have their upsides and downsides. One big downside to all of the platings is that they are plated. All types of platings used are very hard substances, but also relatively brittle, so when the plating fails it starts to chip and flake off, and once they flake off the alumimum is exposed and failure starts to happen. Iron sleeves don't chip and flake.

Platings are also very thin, so the transfer of thermal energy is much higher, aka better at shedding heat.

The big advantage of all of the plating materials mentioned goes back to their very low coefficients of friction. Especially Chromium oxide, which is the best of all in that regard.

The newer ceramic coatings like the one used on the Phantom 85 are not too far behind Chromium in terms of coefficient of friction, but also have other benefits, which is why they are starting to become a new standard. Ceramic lined cylinders, like iron, are more porous, so they do a good job of retaining oil. They also resist absorbing heat, which improves the thermal efficiency of the engines. And on top of all of that, they still have a lower coefficient of friction than iron.

Nikasil is a compromise coating. It's not quite as good in regards to its coefficient of friction as chromium, but has much better durability and some of the thermal efficiency benefits of ceramics since the base substrate is technically a ceramic. It's also more expensive, which is why only the higher end cylinders tend to use Nikasil, and the more budget friendly use chromium.

I could keep going, but this is probably enough materials science for now.
 

DieselTech

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If you got the 49mm steel sleeve engine, you can hone the cylinder with a rigid hone. You want a nice 45°-60° cross hatch pattern. Them steel sleeve engines are pretty forgiving in most aspects.
 

rusty.western.flyer

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Basically, the cylinder cannot be aluminum because the aluminum piston and cylinder would rub against one another, and aluminum being soft it would seize up within short order.

Nikasil is a compromise coating. It's not quite as good in regards to its coefficient of friction as chromium, but has much better durability and some of the thermal efficiency benefits of ceramics since the base substrate is technically a ceramic. It's also more expensive, which is why only the higher end cylinders tend to use Nikasil, and the more budget friendly use chromium.

I could keep going, but this is probably enough materials science for now.
Actually, ally and ally are a non wear surface provided there's an oil boundary layer. Like kinding metals. The problem is the rings. Rings are made of ductile iron, and wear on an iron block/sleeve and has very little wear when there's film strength. Flat head Ford's had iron pistons and soft seats, but also ran leaded fuel.

Nikasil is different than people perceive. It's actually a high silicon content aluminum where you acid wash the cylinders after after boring to expose the lubricant-like silicon. You can't "hone" Nikasil in a traditional sense, and you can't use traditional rings with them, either. I learned the hard way when a fellow brought his 951 (944 turbo) Porsche in for an "ECU tune the stand alone", but in fact had the ally block sleeved, with chrome rings, but the "tuner" was so horrible, the walls washed and polished before the car ever made over 0 GPSI (aka 100kpa), then to my shop. The owner did NOT want to pay for an over-bore, or, a re-sleeve, so he bought a used engine with stock Nikasil cylinder walls. Problem was, he had a HUGE turbo on it, and I told him the motor wouldn't hold. He was driving on the test drive, as soon as that 60mm turbo hit 5psi, we were killing mosquitoes on the highway. The smile on his face was priceless, he said"the car never made boost, or went that fast". Problem was, the pistons rocked and scored the bores....one of my "told you so" without actually saying it out loud to a client.

My work load is generally BMW. In the early turn of the century, they went to Nikasil. Won't go into it further, but the tech is out of hand. No need for a throttle body, the ECU will change the valve lift based on desired RPM/load, both cams are variable, everything is drive by wire (DBW) these days. Bascially if you have a car produced after 2010, it's kinda like a tablet, more than a ICE vehicle.

EDIT: Been on ST for many moons........ LINK
 
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