Villiers Mk25 Opal Field Liberation

Hey guys first post on a forum so bear with me.

The story starts a year odd ago with a little honda motorbike and a chain and ends with 2 beautiful mk25 units (don't quote me on the engine just yet as i id'd it of floogle) one of them was in pretty bad looking condition with no carby and the other ran 10 years ago and the bloke stopped using it. Neither knew what a shed looks like.

Got off my bottom(about time lol) last night and pulled the head off the old rusty machine to find one pretty coked up piston and head (which worked to my advantage keeping the unit clean as it were) and a stuck exhaust valve that wouldn't push up far enough. These little motors astound me as the only flaw in it was the exhaust push rod had dropped its cap and wasnt pushing the valve clear enough. Removed the cylinder pot to find a beautiful set o' rings and a clean piston. Sat the little unit on its back and undid the sump and here i am thinking "here we go, how bad is it?". Well the answer was laid out in no time, not a bit of rust in that crankcase. continue undoing the oil pan thing for the piston, find a weird twisted copper wire split pin setup (bodgey methinks will find out with this other motor) on the bottom of the conrod. Sidecutters away and 9 mil socket in hand i pulled the big end bearing bolts off and expect it to come away easy, needless to say it needed some coercion (Ball Pein and copper driff). In for smoko now Letting you gents know about the exploits of the Opal Fields. I will post more as i do more but for now, im off.

hi there
and welcome to the forum
mk25 villiers
all have castle nuts and split pin on the studs for the bottom end of con rods mate
i have restored a fair few villiers over the last few years and the 25s always seam to suffer most with the exhurst valves seizing up in some way
also watch that the guvernoir nylon gear stud it fitted correctly and good and tight as these can come loose over the years and then the engine
blows a hole though the side of the block,
any advice of info just post on the forum and or pm me and will help you were i can
kev

Thanks for the info on the governor kev going to add images, thought that a thin copper wire would not do for a split pin. Cheap fix around here mate as we all run generators for power. it was no doubt running an old holden (12v car) alternator or the like.

ericthommo wrote:Thanks for the info on the governor kev going to add images, thought that a thin copper wire would not do for a split pin. Cheap fix around here mate as we all run generators for power. it was no doubt running an old holden (12v car) alternator or the like.

true eric mate
better than nothing at the time of repair , me thinks lol

if you send me the numbers of the bronze/brass part of the flywheel
i maybe able to date the engine for you ,
if marked the same as the uk engines from the victoria factory
if my memory is correct there was i think a austrialian factory at one time

i believe that the factory was in Ballarat Vic Kev, i dont have the numbers with me but i will definately take you up on the offer to date the little engine.

Pulled the head and cylinder pot on the "clean" engine to find it filthy. Top ring on piston in 6 pieces, water in the sump, rust buildup on conrod and crankshaft and a chewed out cylinder pot. I then took off the sump and have left it to drip. washed the crankcase and head in petrol. Run the guts out of. I need a bit of advice on timing the little engine, i got the specs 3/16 of an inch from T.D.C. The motors have the same head but different barrels and pistons. Rebuilt or different moter? identical twins.

ericthommo wrote:Pulled the head and cylinder pot on the "clean" engine to find it filthy. Top ring on piston in 6 pieces, water in the sump, rust buildup on conrod and crankshaft and a chewed out cylinder pot. I then took off the sump and have left it to drip. washed the crankcase and head in petrol. Run the guts out of. I need a bit of advice on timing the little engine, i got the specs 3/16 of an inch from T.D.C. The motors have the same head but different barrels and pistons. Rebuilt or different moter? identical twins.

sounds to me as you have a mk 20 and a mk 25 mate
they look identical on the out side but one will be a
mark 20 63mm bore 206.5cc or 12.6 cubic inches 1.5hp @1500rpm to 2.7hp@ 3000rpm
mk 25 70mm bore 256.5cc or 15.65 cubic inches 2.0hp@1500rpm to 3.4hp@3000rpm
stroke on both 66.7 mm

please remember to line the stamped markings on the conrod bottom end and shell cap are one the same side as each other
timing on both goes like this
valve timing will be done automaticly when you follows these steps
when you are ready for the carb and guvnoir lever to be connected back to the guvernoir shaft
the carb must be fitted to the engine inlet manifold
turn the governor shaft fully in a clockwise direction
and open the carb lever to the right until it is fully open and then tighten the clamp bolt tightly

hope this helps you
anything else just ask on here
kev
kev
note that the 2 gears engage correctly with the center punch marks on each gear.
the gorveroir gear meshes with the camshaft in any position of the teeth

refering back to your mk20 carb
on your other posting ive answered on there for you
the carb off a mk 20 -25 will work well on both
well i did for me anyway
kev

My Mk 25 was badged up as a C28 which I thought meant it was built in Australia (or India)