Engine build

Wintertime in The Netherlands, a good opportunity to start building an M72 engine that’s been lying in pieces in the shed for donkey’s years.
The whole project isn’t that big in size so I can do that inside the house 🙂
Because I’m also a photo enthusiast I will try to make as much photo’s as possible to document the whole process and maybe help others with it .

Empty M72 casing
Camshaft with timing gear, bearing and plate.

I made the holes on the timing wheel bigger, with “Natasja” I had the misfortune that the front plate of the crankshaft got loose !! Bolts where tightened but not secured like on the back with a steel wire. Wasn’t done before I overhauled the engine, still a bit inexperienced, so I put it together the way it was ! 2 bolts where out and lying on the bottom, 1 was loose and the one behind the timing gear was loose and damaged ! Took me lots of work, pulled apart almost half the engine to get that one out, so with that knowledge…….. I used strong Locktight and made the holes bigger, just in case !!

Crankshaft with lots of play and found out after pulling apart one big-end was damaged too much . Replaced by a good one.
Brother in law from a UDCN mate, was repairing the crankshaft for me.
Custom made jig.
Pressing the crank apart.
Bearing, rollers and casing.
12 new rollers in bearing. (RC7X10)
Crankshaft, bearing, back- and front plate.
Polish piston set, Almot for 78.2 cylinder.

Both flywheels have diam. 50 for seal, Viton 50x65x10. Left one is adapted from felt to seal, together with back plate crankshaft.

Left flywheel, is made lighter, instead of 5kg it’s now 4.65 kg, right one need some attention. It will be made lighter than the other, aiming for 4kg.
Pins are a bit damaged by the clutch plates, I think I’m gonna replace them with new ones. Later one I have to balance them before putting them on a crankshaft.

After removing material and new pins. Left 4650 gr, right 4370 gr. Markings: TDC, 10, 35 degrees.
Removing almost complete side.
Lot of material gone so a bit lighter.

Pressed the pins out and in at my mate’s shed with a strong press ! He also made a “little helper” to get all the pins the same height ! Yep Cok is a smart guy !

Getting the crankshaft into the casing.
Pfff, it’s in.!
Warming up the back plate, you will get it easier on the bearing.
Timing gears, front plate, seal and breather.

Make sure you got the right breather, there’s a difference in timing !
Check it by putting it in place and see if the hole is for the downpipe in the front plate when the con-rod’s are almost or complete inside the housing.

On a few engine houses I made a peep-hole for the timing of the motor.

Remark; if you remove the side from a flywheel, the hole needs to be further to the front to see the markings on the flywheel (found out later).

Drilled a hole.
Tidy it up with a rubber cap

Muerto superior, верхней мертвой точки, Pointe morte haut, OT-zentrum, Morto superiore are some translations for Top dead-centre, we will keep it at TDC.

Aligning for the proper TDC
TDC, pistonhead makes contact, do this for a few times and you will be able to make a mark on the flywheel.
Little tool for finding the proper TDC.

With this little tool you can find the TDC and mark it on the flywheel. 10 degrees back you can make a mark for the ignition of the engine. This work makes life easier in the future.

Made markings, TDC, 10 degrees and 15 degrees before TDC.

Next thing to do is flowing the cylinders, there’s a lot to gain on flowing the intake and exhaust ports ! There not even, left and right, also as rough as ! Did already a bit but will put some more photo’s here. When the work is done hopefully successfull 🙂 When that’s done they have to be bored and honed on the right diam. The valves need a bit of attention too, a difference of 3 gram between them and maybe get some more weight of them also ! Piston pins have a different weight also and I have to check the pistons on weight when I have them !

Left cylinder, more than 10 mm difference in height, inlet and outlet valve guides .
Right cylinder, about the same difference as left cylinder.

Flowed it a bit.
Same as left, needs a lot more work.
Made a bracket for ignition coil, 3 Ohm double spark plug out.

Think I’m gonna use these Iridium plugs, have to test them on Natasja first.
Installing the clutch, single plate. using and old axle with splines to centre and 3 long M8x1 bolts to get it in place. After that is done use 3 right size bolts or screws to fasten with a bit of Locktight and a centre-punch to fix it.

work in progress