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Author Topic: The Anatomy of M12 Engine  (Read 575 times)

seuguy

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The Anatomy of M12 Engine
« on: August 09, 2020, 01:16:04 am »
Hello everyone, this is my first post in this forum. I am also a new owner of Jin’s M12 engine. I learned a lot about this engine from this forum, so I wish I could do my share of contribution. I disassembled my engine entirely to see what is going on inside this little gem, here is the photo of most of its parts.
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seuguy

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Re: The Anatomy of M12 Engine
« Reply #1 on: August 09, 2020, 01:34:33 am »
Overall, the engine parts are precisely machined and put together, there is one thing I want to point out, that is the softness of the crankshaft. You can see from the pic below the there are severe scratches (dents) on the shaft caused by the set screw of the flywheel. Besides that, the shaft is even slightly deformed, that I can feel it by touching it with my finger. It was a pain to separate the flywheel from the shaft, since the flywheel just stuck on the shaft. I believed that due to the softness of the crankshaft, any excessive force will bend or damage the shaft, which is fatal to the little engine. So please be careful and gentle when you disassemble this engine. [ Guests cannot view attachments ]
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seuguy

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Re: The Anatomy of M12 Engine
« Reply #2 on: August 09, 2020, 01:59:46 am »
The crankshaft is one piece of solid steel, beautifully machined. You can see the mark by the gear set screw. 2 brass bearing was insert between the ball bearing and center weights, which I think is a good design. [ Guests cannot view attachments ]
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seuguy

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Re: The Anatomy of M12 Engine
« Reply #3 on: August 09, 2020, 02:06:38 am »
Inspired by Red, I inserted a thin shim under the C clip, the result is good, the lower rock arm are now moving in a more stable manner. [ Guests cannot view attachments ]
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seuguy

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Re: The Anatomy of M12 Engine
« Reply #4 on: August 09, 2020, 02:15:49 am »
Here are some other pictures. [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ]
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yozhek

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Re: The Anatomy of M12 Engine
« Reply #5 on: August 09, 2020, 07:48:40 am »
Hi Seuguy,

Great post, i don't own one of these but it is always interesting to see inside  ;D  I see Jin made some improvements over the old M90 design.

Warm welcome to the forum!  and thanks for sharing.

Best wishes
Ade
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RedRyder

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Re: The Anatomy of M12 Engine
« Reply #6 on: August 10, 2020, 07:31:46 am »
Welcome aboard, Seuguy!


Nice work with this write up and picture tour.
Thank you.


Gil
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MasonvilleEngines

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Re: The Anatomy of M12 Engine
« Reply #7 on: August 13, 2020, 04:03:21 pm »
Alternative fueling ideas...
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seuguy

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Re: The Anatomy of M12 Engine
« Reply #8 on: August 13, 2020, 06:03:38 pm »
This youtuber should have learnt more about this engine before filming it.

Seuguy
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RedRyder

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Re: The Anatomy of M12 Engine
« Reply #9 on: August 13, 2020, 08:03:12 pm »
I would agree.  I left him a comment that mostly covers it.


This:

Thanks, I enjoyed your video. No one I know ever claimed it is the best of the best. It might be the best you can get for under $300. You might want to learn just a little more about the engine before you shoot the next video. This takes nothing away from the enjoyment of watching you having a little fun. The water hopper is not resting on a solid engine block. It has a wet cylinder which dumped all your water into the crank case when you slid the cylinder forward. The mixture was just part adjusted. There is another jet adjustment at the base of the throttle lever. Use a small screwdriver to adjust. The main bearings did not go bad while you ran it. For some reason these guys like to assemble their engines with a slightly undersized crank shaft. The bearings were loose before you started it. All of their engines are loose at the mains like this. Also the mains are needle bearings. When you seized it up you made the mistake of running a fuel mix of 2 gases with no lubricant. It likes to run on Coleman fuel mixed 15 to 1 with Marvel Mystery Oil. Two cycle oil will also work fine. Any other pure gasoline (no methanol) like 100 octane low lead aircraft fuel or fuels designed for yard tools and other small engines. If you mix oil with your fuel, you will not seize it. You also don't need to fill the crank case with oil. A drop of oil on either side of the crank shaft where it meets the bearings and the oil will wick right in instantly. You can put a drop or two on the big end of the connecting rod though the back plate. I drilled a couple holes in the crank cover so I could put a drop of oil on the piston skirt with a needle oiler. You didn't wear out the camshaft either. It did not have a lot of lift to begin with. If anyone is interested in keeping one together, here's my contribution
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