Need education on 2 cycle oil for an uncommon application

[Countryboy19]

I have a Swedish 2-cycle gas powered jackhammer/rock drill (Pionjar 120) that species a 1:12 mix ratio. That seems excessive to me. I think that was probably an appropriate ratio with the oils available when it was made but I'm not sure that is still the case.

It is 185 cc, air cooled, cast iron cylinder, 2850 rpm engine with the cylinder down (crank is at the top). This is where it gets interesting. The combustion chamber is 2 opposing pistons, the lower is connected to the hammer mechanism (pic attached for the visual folks). There is no normal throttle (there is an adjustment that requires a screwdriver); the compression is really low until you push down on the hammer providing back pressure to the 2nd piston raising the compression. The engine runs rough and slow until this force is applied which acts as a sort of automatic throttling mechanism. The hammer mechanism is lubricated by oil left after combustion passing down into the lower parts of the mechanism (some seepage past the rings of the lower piston, some through a special port).

The oil specification is: the discontinued manufacturer's specific oil or "a recommended 2-stroke oil".

Considering the much better quality oils available today is it really necessary to run that much oil? It's going to be costly feeding this thing that much oil. I'm thinking it would be better to get a quality oil and run it at 1:20 or so instead. But I'm very overwhelmed with oil specifications and need a little guidance. Any thought or guidance that may help guide me? This thing isn't running at high rpms (and it's a low temp spark plug) but it will see continuous full-throttle use while deep hole drilling in rock. I want to keep it lubricated but not break the bank!

 

[Whimsey]

Maybe they want the mixture oil rich because as you said the left over combustion mixture oils the cylinder below

 

[ripcord]

How old is this unit? "Back in the day", 2-cycle engines used to have bushings on the crank instead of roller bearings so the bottom end needed a lot thicker mix.

 

[ripcord]

Apparently, the Pionjar 120 is still being made in China. Maybe a knockoff?

Pionjar 120 Jack Hammer Suppliers & Manufacturers - Factory Direct Price - GMD Equipment

Find professional pionjar 120 jack hammer manufacturers and suppliers here. We're offering high quality pionjar 120 jack hammer with competitive price, please rest assured to wholesale bulk products for sale here from our factory.

www.gmd-eqpt.com

 

[Chris142]

How old is this unit? "Back in the day", 2-cycle engines used to have bushings on the crank instead of roller bearings so the bottom end needed a lot thicker mix.

Ya.bearings or bushings?

 

[Countryboy19]

Maybe they want the mixture oil rich because as you said the left over combustion mixture oils the cylinder below

Yes, for sure oil rich for that reason but this thing slobbers oil everywhere. I think modern oil doesn't burn up like older oil did so there is too much passing down to the hammer.

Apparently, the Pionjar 120 is still being made in China. Maybe a knockoff?

Pionjar 120 Jack Hammer Suppliers & Manufacturers - Factory Direct Price - GMD Equipment

Find professional pionjar 120 jack hammer manufacturers and suppliers here. We're offering high quality pionjar 120 jack hammer with competitive price, please rest assured to wholesale bulk products for sale here from our factory.

www.gmd-eqpt.com

That's definitely a knock off. The original Pionjar units are made in Sweden by Berema. Berema was acquired by Atlas-Copco and the Pionjar units aren't made anymore. The originals were about $6000 when new. The Chinese knockoffs are, well, Chinese knockoffs.

Ya.bearings or bushings?

Captive needle bearings.

 

[ripcord]

At 12:1, I would think you would definitely want a low/no ash 2-cycle oil. Also, if you run it with a significantly lower oil ratio, it might not run very well as the jetting in the carb takes the mix ratio into account. The less oil, the more gas, so the effect of less oil is a richer fuel/air mixture.

 

[Warlord]

At 12:1, I would think you would definitely want a low/no ash 2-cycle oil. Also, if you run it with a significantly lower oil ratio, it might not run very well as the jetting in the carb takes the mix ratio into account. The less oil, the more gas, so the effect of less oil is a richer fuel/air mixture.

I was thinking along the same lines. A cheap tcw-3 would probably be suitable. At the low rpm of this machine it’ll probably combust a little better than a TC oil and be a bit cleaner while still giving all the lubrication it needs.

 

[Countryboy19]

At 12:1, I would think you would definitely want a low/no ash 2-cycle oil. Also, if you run it with a significantly lower oil ratio, it might not run very well as the jetting in the carb takes the mix ratio into account. The less oil, the more gas, so the effect of less oil is a richer fuel/air mixture.

Funny you mention that, I planned to address that in the OP and neglected to. There is an AFR adjustment knob on the top so you can adjust it on the fly. I suspect that's because of the high oil ratio and the fact that some oils combust better than others so they realized the need to be able to easily adjust the AFR.

This thing is basically set WOT all the time with only 2 user controls on the top, choke & AFR.

 

[Imp4]

Here's a neat video on maintenance on this unit.




And this link shows that the oil the OEM sells is plain old SAE-40 non-detergent oil for the mix.
You could probably dump molasses into that thing and it would run fine.

 

[ripcord]

And this link shows that the oil the OEM sells is plain old SAE-40 non-detergent oil for the mix.
You could probably dump molasses into that thing and it would run fine.

Imp4, I think you win BITOG for the day for your definitive answer for an esoteric question and your superior google-foo

 

[Countryboy19]

Imp4, I think you win BITOG for the day for your definitive answer for an esoteric question and your superior google-foo

I concur. I've searched a TON on this. I found the video he posted but never did see the info on SAE 40 non-detergent oil being the recommended oil.

 

[Metabird]

It is 185 cc, air cooled, cast iron cylinder, 2850 rpm engine with the cylinder down (crank is at the top). This is where it gets interesting. The combustion chamber is 2 opposing pistons, the lower is connected to the hammer mechanism (pic attached for the visual folks). There is no normal throttle (there is an adjustment that requires a screwdriver); the compression is really low until you push down on the hammer providing back pressure to the 2nd piston raising the compression. The engine runs rough and slow until this force is applied which acts as a sort of automatic throttling mechanism. The hammer mechanism is lubricated by oil left after combustion passing down into the lower parts of the mechanism (some seepage past the rings of the lower piston, some through a special port).

Very interesting design. Like Whimsey said they probably say to over oil to make sure the bottom crank case is getting enough lube from the top. Is this like a personal machine or something you use to make money? I've no idea of parts availability but I would probably run the recommended amount if it was me and parts are scarce/use it to make money.

Not sure when these were made but that is a lot of oil for sure. Even 1:20 is a lot. Apples to oranges probably but several old snowmobiles my dad and I own say 20:1 on the fuel tank and we run 40:1. Dad usually uses a cheap tc-w3 but I'm a little more picky than that. I like to run a FD rated oil in 2 strokes myself but nothing I own is comparable to your hammer.

But I'm very overwhelmed with oil specifications and need a little guidance. Any thought or guidance that may help guide me? This thing isn't running at high rpms (and it's a low temp spark plug) but it will see continuous full-throttle use while deep hole drilling in rock. I want to keep it lubricated but not break the bank!

I have attached a little sheet with some info about 2 stroke oil specs. As Imp4 stated if this thing ran on 40 weight ND it will probably be happy on almost anything you choose. A gallon of Walmart Super Tech TC-W3 is $16.74 where I live and may be a cheap choice for you.

 

[Cujet]

In our two cycle engine oil testing, we found that more oil made more power. All the way down to 8 to 1, unfortunately that ratio was difficult to deal with and our outboard race engines simply did not like to idle or operate at low RPM with that much oil. We settled on 16 to 1 as being the most practical race-engine ratio. With excellent power output and no operational problems.

One thing to keep in mind, while two stroke oils today are better,, they are not significantly better lubricants. They simply produce less smoke, far less carbon, prevent piston ring sticking and so on. The lubricity of 30-40 viscosity oil vs. Bright Stock (a two stroke oil base) vs. polybutene is not significantly different. Put another way, two stroke oils from the 1950's to today can protect your engine from excess wear when used in appropriate ratios.

 

[Countryboy19]

Very interesting design. Like Whimsey said they probably say to over oil to make sure the bottom crank case is getting enough lube from the top. Is this like a personal machine or something you use to make money? I've no idea of parts availability but I would probably run the recommended amount if it was me and parts are scarce/use it to make money.

Not sure when these were made but that is a lot of oil for sure. Even 1:20 is a lot. Apples to oranges probably but several old snowmobiles my dad and I own say 20:1 on the fuel tank and we run 40:1. Dad usually uses a cheap tc-w3 but I'm a little more picky than that. I like to run a FD rated oil in 2 strokes myself but nothing I own is comparable to your hammer.


I have attached a little sheet with some info about 2 stroke oil specs. As Imp4 stated if this thing ran on 40 weight ND it will probably be happy on almost anything you choose. A gallon of Walmart Super Tech TC-W3 is $16.74 where I live and may be a cheap choice for you.

It's a personal machine but I use it to "save money". I have a lot of shallow rock on my farm. When setting livestock fence if I hit rock I bore a 2" hole in the rock and set a t-post in the hole. When I encounter a rock too large to move when digging I drill a hole and set charges that turn it into lots of little rocks. Getting professional blasters out is big money.

 

[ripcord]

Is there a separate reservoir of oil or grease for the hammer part of the tool or does the mix lubricate that, too? I wonder if that is why it needs such a thick mix? I know nothing about jack hammers.

 

[Countryboy19]

Is there a separate reservoir of oil or grease for the hammer part of the tool or does the mix lubricate that, too? I wonder if that is why it needs such a thick mix? I know nothing about jack hammers.

Modern gas powered hammers and air powered often have a reservoir or inline oiler for the hammer mechanism. This particular gas powered one gets its oil from the gas mix. In the attached picture the red arrow points to a port coming from the combustion chamber passing into the lower part of the hammer mechanism. Exhaust gases containing oil blow down through that port lubricating the hammer. The gasses go on to blow down through the hollow drill steel, and out the bit at the bottom of the hole, ejecting the stone dust. The blue arrow points to the lower piston & hammer (all one piece). When the combustion takes place it provide a sharp downward force, not quite as impactful as a pneumatic but still effective. Yes, this robs the power from the upper piston but the only power the upper piston needs is just enough to turn the crank for another compression stroke because no power is being pulled from the crank (other than cooling fan and ignition system).


BTW, I called the company linked above, Creighton Rock Drill. They can get all the parts except one of the handles, they offer rebuild services, tooling, oil, and even a replacement air filter (I thought I found and purchased the only remaining air filters in existence on ebay).

ETA, Creighton's expert Dennis said they're VERY good, better than anything made today. He blames the US for them being discontinued. After the EPA banned their import Berema stopped making them because the US was a significant part of the market. He also said the Chinese copies aren't worth even considering, their performance isn't even close to that of the original. That's reassuring to me.

 

[Countryboy19]

Here is my unit in the crate. My dad bought this military surplus about 13 years ago. He said he couldn't get it to run right. I'm surprised he got it to run at all considering the fuel line was disintegrated and missing, I think his memory is a bit foggy. My brother helped me replace the line (it took 4 hours because this thing is put together like a puzzle) and we got it running. The only tool it came with is a clay spade. We were able to chisel out frozen gravel in my brother's driveway with the clay spade. I'm starting to acquire the tools to drill holes in rock so I can blast rock and/or set fence posts in rock.

 

[Imp4]

That thing must smell like a major environmental incident when it runs.
Can you repurpose it as a fogging machine???

 

[Countryboy19]

That thing must smell like a major environmental incident when it runs.
Can you repurpose it as a fogging machine???

Haha, that's part of the reason I was wanting to reduce the oil a bit but I guess I'll leave it at 1:12 for now. It does produce a lot of smoke which may be part of the reason for the whole EPA thing...