Villiers XIIC 148cc doesn’t run anymore

[Albion EJ]

Need help!
My Villiers XIIC 148cc long stroke engine has been running briefly and then it has no stroke. I have already done all sorts of things; replaced gaskets, new spark plug, reset timing, had cylinder loose, disassembled carb etc.
What is striking is that even after many start requests, the spark plug is not wet. Carb is a 1 1/8" Villiers with needle adjustment, needle 4.5 and nozzle 2, so should get quite a bit of petrol.

But what am I overlooking? Is it sucking in false air through the bronze bushings on the crankshaft?

Any tips welcome as I don't know any more.

[33d6]

Personally, it sounds like a fuel problem. Not enough fuel getter to the carburettor. Could be anything from a blocked air hole in the petrol cap or half blocked fuel tap but I particularly distrust modern in-line fuel filters. They are not made to to pass a mixture of petrol and oil.
Best of luck.

[R]

Does this particular carb have a tickler mechanism.
Nothing visible in the pics.
But could be t'other side.

Or, can that air cleaner (?) be choked.
Even by putting the palm of your hand over something strategic.

Agree, gravity fed fuel strainers are a peril.
Not much gravity in that short distance !

[Albion EJ]

Thanks!

What about the positioning of the piston?
Is this the right way?

You are looking at the left side of the engine as you can also see the “L” on the case.

[33d6]

Yes, that is correct. The vertical surface of the deflector  faces the transfer  port.

[cardan]

Is it sucking in false air through the bronze bushings on the crankshaft?

It will if the main shafts or the bushes are worn: the shafts and bushes need to be round with only a thou or two clearance (say 0.025-0.05 mm). You definitely should not feel any movement if you grab the flywheel and try to move it up and down. If it clunks you're in trouble! The other place that wear occurs in early two strokes is in the bore: not so much up the top (as it is in four strokes) but above and below the ports where the rings jump across. And the rings, of course.

If these parts are worn the bike will probably still run, but will get hot an bothered when riding. If you've got good compression - it really should be quite "sharp" as you kick it over - then wear is probably not the problem at the moment.

Leon

[33d6]

Villiers advised up to .008” wear was acceptable. Whether bushes or crankshaft are worn is irrelevant. It is combined wear that counts. Essentially though, if it’s an easy starter, leave well alone. I find the major problem with old Villiers engines is that owners can’t resist pulling them apart to then find they’re never quite the same afterwards.
I think the fussiest area revolves around the ignition timing and the points. The points cam is on the end of the crankshaft so is directly affected by mains bush/crankshaft wear plus the points pivot hole in the points box wears so the action of the rocking pivot point gets erratic. It’s fascinating to watch when using an ignition timing light. You have this blurred line wandering 4-5 degrees each side of the timing line.
I don’t worry overly much about overheating. All cast iron fixed head two-strokes running a cast iron piston run hot. They cannot do otherwise. Just be enthusiastic with the oil.

[R]

And the good thing about iron pistons in an iron bore is that they'd
have to get REALLY hot to think about nipping up, let alone seizing.

Even without much/any oil being in sight - thats the beauty of cast iron on cast iron.
The carbon in the crystal iron lattice makes this possible.
Without this, the old bike industry, with drip feed lube would never have prospered ?

[Albion EJ]

All thanks!

Indeed the bush on the right side is worn.

Any option to buy new ones to be fitted on the polished main shaft?
Or just have a copy made?

[33d6]

If you have pulled the engine apart and removed one bush it is best to replace the bushes on both sides to make a proper job of it. Replacing one bush alone is usually just a short term repair, replacing both has long term benefits.
I don’t know of anyone supplying these bushes but as they are so easy to make I just make my own. They can be made of any common phosphor bronze bearing material, there is no benefit in using anything fancy or special. This is a very ordinary job for any skilled machinist.

[cardan]

Ditto. Also time to check the main shafts for wear and roundness - the wear is some distance in from the end so if the shafts are not parallel and round your new bushes will be wasted.

Also the bushes need to be in line when you're all done. I usually make them a thou (0.001") under size, then ease them out with an adjustable reamer fitted with a pilot. The pilot fits into the bush in the opposite side of the crank case to keep the reamer parallel while its cutting. Not a difficult job, but you need the right tool. (I borrow my adjustable reamers from a friend who has a boxed selection - last forever if only used on phospor bronze.)

Leon

[33d6]

There isn’t much comfort in checking the mainshafts for truth. New mainshafts aren’t to be had. Villiers mainshafts of the period are integral with the flywheel. They can be be ground circular undersized up to .005-.010” off but the centres have to be unmarred and dead true plus be set up dead true to the big end assembly. Not an easy job. I’ve chewed this job over and over, reluctantly coming to the conclusion it’s probably just as easy to make the whole assembly new from scratch. Either way is a drama.
On the plus side the two crankshaft halves are identical which is both a blessing and a curse as it both makes the job easier but is wide open for enthusiastic owners to unwittingly end for end the crank assembly when putting things back together. The wear patterns are different for each side so end for ending speeds up the wear rate until the original patterns reassert themselves.
Old British two-strokes are of dead simple construction but quite subtle to get running really well. Charging in with lots of enthusiasm rarely ends well.