As someone who "started over" several times the first time I put a Bultaco engine together... luckily it's not hard to split the cases and just as easy to put them together. After a "few" times I had it down.
That sounds reasonable ratio.
And the spark plug sounds ok.
Is it a Pioneer or MAR?
Spark plugs sounds ok. Gas sounds good. Other than fouling plugs how does it run?
The wrong plugs will foul quickly. But it's hard to find a listing for OSSA. From what I can tell you're probably using the right plug, although if you're going through iridiums that fast you'll soon spend more in spark plugs that the bike is worth.
Perhaps a bad condenser? Or just that the carb is running too rich or perhaps the oil/gas ratio is too much.
I can re-check tonight when I get home but this is the best of my recollection. I have somewhere in my archives a picture of the parts, (it's been a while since I've been into the M49) I like to snap a shot when taking things like this apart. With digital cameras almost free it can't hurt. Especially if you're not intimate with the parts.
Had the same problem. Let see if I can remember what it was. A loose bearing spacer inside the wheel I think. Take off the rear wheel and when you look inside the brake and where the axle goes through there should be a spacer. If not then when you tighten the axle you pinch the hub instead of the bearing.
Just wait till some thing like in Ishy's photo shows up at an ITSA event. Then the arms race will be on. Hope you weren't hoping that Fantic was going to get you by because now it's toast.
Not only lights and a horn but I would think street tires, unless your commute is over the hills and through the woods. Which, if you live in London, might be frowned upon.
The Farm
The huge National is next weekend. You European folks try not to snicker but we had 100 entries for the trials last year. Easily the biggest vintage trials in the US.
Those definitely look like tubes for a bike without the dropped lower yokes. What make mine so peculiar is the great distance between the upper yoke and the knurling. I can't imagine any Bultaco that would support those dimensions (I say this with very little research...)
Gomey, do you bring any of those bikes to Chehalis to ride at The Farm?
We're mostly loaded and leaving in the morning. Anyone else going? I'll try to post pictures this weekend. I'd call it live blogging except I'll be dead tired.