Nemett 15cc 4 stroke engine.

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

wheeltapper

Senior Member
Joined
Jun 25, 2010
Messages
143
Reaction score
14
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.
4strokeengine.jpg


parts so far, cylinder jacket
cylinderjacket.jpg


crankcase nosepiece.
bearinghousing.jpg


part finished head.
partfinishedhead.jpg


and crankshaft.
crankshaft.jpg


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 :big:

cheers
Roy
 
Hi mate
Nice start on a good looking engine :)
Pete
 
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!
 
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!

[ame]http://www.youtube.com/watch?v=7X2pe7BrtT8[/ame]

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...
 
  • Like
Reactions: gus
It sure does sound nice. ;D

have you considered putting wings on the workmate :big: :big:

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
 
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
 
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 :big:
Pete
 
Where can you get the plans for this these days?
 
Hi
back again.

A few more progress pics.

cylinder liner
cylinderliner.jpg


part finished crankcase
partfinishedcrankcase.jpg


and an overview of what's been done.
partlyassembledengine.jpg


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
 
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
 
Thaks anyway Steve, I found a pic of the interior with the holes showing so thats that.

Meanwhile :big: :big:

I dont usually embarrass myself in public but I had to take a pic of this.
poor mans DRO.
can I nominate it for bodge of the year? ???

I had to move the mill table an exact amount for the hole centres of the con rod for this engine.
steel bar clamped to the lathe tray, square clamped to that, digital caliper clamped to the mill vise and the other bit of the caliper clamped to the square.

piece of wood to take out the spring. ;D ;D


poormansdro.jpg


am I mad or what?

Roy
 
Necessity is the Mother of invention...The head is the one part of the engine I felt quite in awe of. I did buy a rotary table, but afterwards did think that perhaps converting all the holes to X-Y co-ords in excel would have worked too. Need a lot of concentration to keep on top of the backlash, but I'm sure it would work.

One thing I learned from building this, was if you make a mistake, finish the part, don't scrap it and start again. That way you get to practice all the ops before starting again reducing the chance of mistakes the second time around and the other thing I discovered was sometimes as you press on, you find away of recovering the error as the work progresses. (My Nemett's head has some scars from being thrown in the scrap...)

Oh the moment when it fires the first time...

Steve
 
Hi all.
Just a couple of pics of the finished crankcase.

Or
how to turn an expensive lump of aluminium into a hole 8)
completecrankcaseback2.jpg


completecrankcaseback.jpg



cheers
Roy
 
Hi
more progress.

piston
Piston.jpg

Piston2.jpg


and from these
carbparts.jpg


to this
carb3.jpg

carb2.jpg

carb.jpg

carb4.jpg


thanks for looking.
Roy
 
Nice work. Love these Nemetts engines. That carby looks great Roy like the rest :bow:

Brock
 
going great Roy
Pete
Keep it coming !
 
I like the carburetor especially... lots of fiddly parts that have to be well-made for proper function.

Very nice! ;D
 
Hi
another landmark reached,
the cylinder head.
top
completehead.jpg

underside
completehead2.jpg

and with carb and exhaust
headalldressedup.jpg


cheers
Roy
 

Your parts are looking great!

Keep up the nice work.

 

Latest posts

Back
Top