classic motorcycle forum

I agree with Rex, kind of look forward to your saga! If the rest of the piston is right, ie. gudgeon pin size, correct shape to the wedge on top then it's easy. Just file the brass peg down and re-locate it, careful work with a hacksaw will cut it clean with the ring groove and making a new pin is easy as you have a lathe. Won't come out as the ring will hold it in and don't cost nothing!
 9 thou ring gap is a bit excessive? However it won't stop it running, don't stop now. Can't say I'm holding my breath but do look regularly to see your latest update.
  Colin

Out of curiosity (that wot killed the cat) is there a felt seal on the plain bush side? If not it would rely on the bush / crank fit to be very good. My M/Debon (admittedly somewhat older than yours) has plain bushes both sides and no seals. Obviously a ball or roller bearing would need a seal hence the felt on that side.
  If there is no seal on the plain bush side it would suggest wear in the bush (and or the crank) so a new bush would be needed and if necessary the crank ground that side. If this is the case, and you feel the felt is a good fit, then by doing the bush the engine would still be standard and shouldn't require machining to fit other oil seals.
  Small Villiers engines have a bronze sealing ring which is pushed against a facing surface with a spring, I would assume your spring should be pushing a washer of some sort against the felt seal to keep it compressed against the crank. A simple but effective system which personally I would prefer to leave in place rather than fit a lipped seal, however your bike so your choice.
  If there is sufficient wear in the bronze bush even if you did fit a seal there's a possibility that the crank rattling a little in the bush could still cause a leak that side with a seal fitted.
  I had a bearing develop play on the timing side of one of my Banatams, I had to change it not due to vibration or noise but because oil / petrol was leaking out and onto the points. The seals were relatively new it was the small amount of play in the bearing allowing the crank to move and the seal to leak.
   As already mentioned, strange looking sight with the ports?

Colin

The battery / coil set up with a different plug lead and plug, completely does away with the magneto side of things except the points and condenser. If it doesn't run with this set up then taking the mag back to Villiers is a waste of time.
  So on the ignition front, using the battery coil, that only leaves the points and condenser to look at. You have fuel, either directly down the plug hole, or by the plug getting wet so it should go BANG.
  I don't know you so have no idea about your experience and knowledge, please don't think I'm being insulting to ask if the timing is 5 mm before TDC not 5 mm after TDC? although it does run on occasions which suggests otherwise. I have seen engines running after TDC and an exhaust manifold glowing like Rudolf's nose!
  Actually I do remember looking at two bikes for people in the past with a very similar problem as yours. One had a standard sized piston in a +40 bore, the other had no piston rings.  Both were bought as "should run with a little fettle-ling?? Although I thought you'd  had the engine apart? You do mention the compression, have you tried a compression tester? Remember with these the throttle must be wide open for a compression test. But............... I seem to remember you riding it a bit last year?

 Colin
 

Many happy ones for tomorrow! At least the new one has pedal power, you'll be able to get somewhere engine or not. I think you need an award for persevere if nothing else, if you look at it as a learning curve you'll get a diploma by the time you're done!!
  If you do change the seals try to find some proper lipped seals rather than O rings, there's some pretty slim ones around. The lipped seals will seal better the more pressure that's behind them, O rings won't seal so well and won't take up as they wear.
  Keep one thing in mind though, the oil seals allow a vacuum to form in the crankcase to draw in fuel and air, they then allow pressure to build in the cases to push the fuel air mix via the transfer ports to the combustion area. Air will always be present in the combustion area if the piston's down so adding fuel via the plug hole you have a "good to go" situation in the combustion chamber. So it should fire, if everything else is correct, even if you take the carb off altogether.
  Even with leaky seals it should run to some degree (with a carb.) once it has started with fuel down the plug hole, hard starting is one sign of leaky seals but the other is the engine revving right up as it sucks air in around the seals so acting as if the carb slide is open. If it slow runs and dies as the throttle is shut off it isn't sucking in air around the seals.
  Not being there to see and experience exactly what's happening makes it difficult to guess what's going on. You can try soaking the felt seals with oil as this will both swell them and give more of a barrier to air getting sucked in and out.

Colin

Be interesting to see how tomorrow goes, from your post I'm assuming you fired it on the magneto? If so it seems a little playing with the mag gets it going for a spell. Be interesting to try it on the battery coil, if you haven't done so?
 All old two strokes will smoke like mad when started on choke and will take up to a 1/4 of a mile thrash up the road to clear themselves out. We were going to a show once and I made the mistake of following three Bantams from my house, being a sociable fella I made everyone a cuppa before we set off so the engines were cold needing choke to start. I couldn't even see the road for two stroke smoke following them, didn't do my lungs much good either!
  My research on my 1926 M/Debon is to run it on a 10 / 1 mix, I had an old Sea Gull outboard years ago and that also ran on a 10 / 1 mix. The reason for this amount of oil is a lack of oil seals, the thicker "brew" helps the plain bearings to seal. Might be a reason yours is supposed to be running oily?
Colin

A drop of petrol down the plug hole eliminates the oil seals from the equation, at least as far as staring is concerned. The seals are only relevant to getting the petrol from the carb to the combustion chamber, put petrol in the combustion chamber and it should go bang. Only two other components are needed for the bang, compression and a spark at the correct time.
 Compression on your engine is down to two things, piston and rings being good or the head gasket. Usually you will hear a head gasket, or since you've had it running see some external sign on a leak. Older small two strokes often appear to have very little sign of compression compared to a 4 stroke. One thing which will alter the compression felt is having the carb totally closed, this restricts the air entering the engine therefore how much gets gathered on top of the piston to get compressed.
 Going the battery coil route is always a good test route, only one wire needs to be led into the magneto to the points. Battery pos. goes to the coil, battery neg goes to earth on the engine and the other low tension wire from the coil goes to the points and condenser. Since this doesn't involve the bikes electrics in any way either a 6 or 12 volt coil can be used, just use the relevant battery for the coil.
 Timing can be checked simply by turning the engine over from the flywheel with the coil in circuit and the plug will spark when the points start to open. If not you have a points / condenser issue. Perfect way to test how you've timed the engine as you'll get a spark you can see as you check the piston height BTDC.
  You must be able to get either a cheap coil (older car or bike) from a breakers or cheap off eBay. To test an old battery coil simply put a plug lead into it and a plug, earth the plug to the neg. of a battery and take a pos. and neg. wire from the battery to the low tension side of the coil. Fix one wire and touch the other to the terminal on and off, every time you take it off the spark plug will spark.
  This is all you're doing with it on the bike except the condenser will stop the points from getting burnt by reducing the current across the points face.
  If you intend to have another project bike in the future having a test coil sitting on the shelf ain't such a bad idea?

Colin

Sounding promising!
Colin

Don't let it beat ya! Thinking logically................. You sorted out the points, re-timed it and it started right away?? Two things occur to me, 1 is the amount of fuel in the crankcase had evaporated to a point where it was ready to run? However my inclination would be to look at the points again. It was running, then running hard so........ Perhaps the points, timing have moved? or if there's a problem with the condenser it wouldn't take long for the points face to get burnt putting you straight back to square one as soon as the engine ran for a short while.
  As a point of interest which might or might not have any bearing. The wico pacy mag. on the D1 Bantams originally had a physically large condenser which you just can't buy anymore, the current ones for sale are about half the original size although they're rated the same. I kill condensers on one of my Bantams.
  My electrical knowledge is limited to say the least but I've formed a theory and a bit of trial and error seems to confirm this. When I first bought my GPO Bantam and got it running I came to the conclusion that it was dangerous to be on the road, at least with 6,2" and 15 stone of me on it. The performance was so slow, especially on any sort of incline, that I had a line of cars behind me all itching to get past. But I loved the look of the bike so decided to do some tuning on it to get a bit more "get up and go"
  Happy days! It's now capable of not being a hazard on the road and I've been using it for 6 years or so, even commuting to work on it some days. But............ The tuning means it revs much more freely and basically when I ride it there are only two throttle positions, on or off.
  My theory with killing condensers is since I'm almost constantly revving the nuts off it the HT coil is over generating and killing the condenser, remember the ones available are only half the size of the originals. I'm thinking they're kind of like a battery, think of an AA battery and a D battery. Both 1.5 volts but one with a much larger capacity, a re-chargeable D battery would stand a much higher input charge than the AA battery.
  A condenser is just two sheets of aluminium foil rolled around each other with an insulating sheet in between them, double the size of the condenser means double the size of the sheets of alli. therefore more able to absorb a higher current flow from the magneto. To test this theory I tried all kinds of different capacitors of the same value but ultimately they all failed. Then I tried two condensers and hey presto it's been fine ever since!
  I have a friend locally who's getting a bit old and doddery, he also has a D1 GPO Bantam which is more an ornament than a rider. Last year we took this and his B 175 down for MOT's booked one after the other. I had fitted a new condenser and points in the D! about a week before and apart from a quick blast up the road the MOT was the first run since fitting them.
  He rides very slowly and cautiously and stalled it at a busy roundabout and couldn't get it started. We swapped bikes and I got the D1 going first good kick, then thrashed it the last 4 miles to the MOT shop. I mean thrashed it! Since he was on the 175 he could keep up.
  About a mile from the shop it started missing and popping, we made it and got the MOT's but I had to take the points out and file them to get it home, about a mile from home it started missing and popping again.
  Basically the new points and condenser lasted about 5 miles. Did he stall it because the condenser was failing after a couple of miles? For me it started straight away and rode off fine for a few miles, or did my thrashing it cause the condenser to fail?
  Condensers are far more important for magneto's than battery coil ignition systems. Battery systems have the power from the battery to create a spark so the condenser is more to stop a fat spark at the points from burning the faces. Magneto's generate only a small amount of power to create a spark, there's a resonance between the coil and condenser which supplies a little more power to the coil to produce a better spark. So with a magneto the condenser is performing 2 tasks one as a spark booster and the other to stop the points face from burning.
  You had starting problems, changed the points face for nice new ones and the engine ran straight away. It revved it's nuts off and now it won't start, maybe I'm biased with the problems I've had with Bantam magnetos, specifically condensers, but........... Taking the points out again and examining the faces might give you a clue, there shouldn't be much going on with the points faces with only such a short running time. If there is anything then suspect the condenser.
  Unfortunately your swapping around with carbs. is further complicating things as none of them are really a known quantity, although you seem to have one which is basically working. However I can't help but think your starting issues are more ignition based.
  Sorry for once again writing a novel, I have too much time sitting around right now with the knee!

Colin