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Old 07-29-2011, 07:41 PM   #1
wheeltapper
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Default Nemett 15cc 4 stroke engine.

Hi people, well I've finally bitten the bullet and started building this engine.
this won't be a blow by blow account, rather a show and tell as I (hopefully) finish a part.

It will also take me a fair amount of time as I have to save for the material and tooling required, I've already come to a stop on the head because I need a rotary table and they don't grow on trees.

first a pic of what it should look like.


parts so far, cylinder jacket


crankcase nosepiece.


part finished head.


and crankshaft.


That's it so far.
next is get a square lump of ally for the crankcase.
expensive hobby this, ain't it

more to follow soon.


I hope

cheers
Roy


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Old 07-29-2011, 09:32 PM   #2
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Default Re: Nemett 15cc 4 stroke engine.

Hi mate
Nice start on a good looking engine
Pete


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Old 07-29-2011, 10:10 PM   #3
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Default Re: Nemett 15cc 4 stroke engine.

These Nemitts are little charmers. With their cylinder head and cylinder looking like one piece, it offers the illussion of a low profile, streamlined OHC design!
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Old 08-09-2011, 08:24 PM   #4
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Default Re: Nemett 15cc 4 stroke engine.

It's a nice engine to build - my first project. Using the excuse that it was my first engine, I built it as a glo motor and avoided all the electronic ignition and associated parts.

It does run well, but very smoky!


When it was finished there was no compression on the engine, the piston and rings were a very good fit so pretty obvious it was the valves not seating properly. I went to tremendous lengths to get the valves to seal but no joy. (Do not trying grinding them in it makes things worse!). In frustration I used my dads old trick and put some engine oil in the cylinder put the plug back and spun it up with an electric starter. It fired a couple of times and as if by magic there was loads of compression...
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Old 08-09-2011, 09:19 PM   #5
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Default Re: Nemett 15cc 4 stroke engine.

It sure does sound nice.

have you considered putting wings on the workmate

I think I'll be going for glow ignition, the electronics isn't my cup of tea.

hopefully my one will someday sound like that, not as smoky I hope, I can see you put engine oil in it. :P

Roy
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Old 08-10-2011, 06:49 AM   #6
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Default Re: Nemett 15cc 4 stroke engine.

Nice start,Roy.I too love the sound of four strokes,they sound much more natural than a screaming 2 stroke.
This one is on my ever growing to-do list.So many projects,so little time
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Old 08-10-2011, 07:47 AM   #7
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Default Re: Nemett 15cc 4 stroke engine.

Hi Steve
Congrats on first pop
BTW. If the problem was with the valves mate the oil would have made no Difference
you might have a piston/ring problem. It may even just need bedding in

My 2 cents
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Old 08-15-2011, 09:59 PM   #8
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Default Re: Nemett 15cc 4 stroke engine.

Where can you get the plans for this these days?
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Old 08-16-2011, 03:44 PM   #9
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Default Re: Nemett 15cc 4 stroke engine.

Hi
back again.

A few more progress pics.

cylinder liner


part finished crankcase


and an overview of what's been done.


and a question for Steve Withnell, when you made yours, the bolts that hold the mounting angles on, did you drill right into the crankcase then seal them or are they blind holes?
I can't figure it out from the drawing.

thanks for looking.
Roy
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Old 08-18-2011, 09:55 PM   #10
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Default Re: Nemett 15cc 4 stroke engine.

To be honest I can't remember. I don't think it matters though as I don't think there is any pressure to speak of in the crankcase. The petrol version has a breather to the CAM shaft, and the box isn't sealed.

Steve


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