Nice Jacket, I really like the Ducati Meccanica design, so much so that I removed the Scrambler badges from my scrambler tank and replaced them with stickers View attachment 176817
The replacement carbs arrived, unfortunately one of the mixture screws was seized, it was the devil’s own job to get it out, here for reference is what I did, fill the recess (tower) that the screw sits in with plus gas and left it for 48hours, applied heat with a mini blow torch, attempted to unscrew, zero movement, repeated the above, zero movement, cut the tower off far enough that I could grab the screw with pliers, no movement, more heat, fractional movement left and right, continued to apply heat/oil and work screw in both directions, movement increased slightly, cut a new slot in the brass with a hacksaw, continued to work both directions and apply heat and oil, gradually worked up to a full turn and then managed to unscrew it, it was extremely tight as it came out, looked at the threads on the screw and carb body and they looked perfect!, put some oil on the screw and it screws in and out fully and smoothly, fitted a new screw with a small amount of copper grease on the threads So no corrosion evident, apart from black staining in the roots of the threads on the screw, unbelievable how these things manage to seize themselves in, so onward and upward Here’s a photo of the remnants of the screw :0
I too have suffered with the pilot screw seizing (once on a 750SS and once on a M900). I think the main problem is the rubber plugs going AWOL - no matter how secure they seem when you put them back they are not there when you come to look again about 6 months later - maybe a dab of silicone sealant would help. With my current M900 rebuild I decided that a more definite method of protection was required so I knocked up some caps from some 13mm Hex aluminium bar. The recess in which the jets fit will (without drilling) take a ground flat plug 8mm tap for about 4 threads before the tap hits the jet. Note also the carb heater hose holes (it is unlikely to get used in the winter) similarly capped and the replacement of x head screws with stainless cap screws
That’s a neat solution to the caps (above), I can no longer use the rubber cap on the one that I’ve cut the tower on but I’ve found some thin wall rubber pipe that grips onto what is left of the tower, so I’ll blank one end of the pipe or glue it flat at one end and shove that on, maybe rotating the screws and returning them to position once a month will also help, I’m out on the bike now with the replacement carbs fitted, early indications look good, just pulled over for a coffee and left it on tick over, I can’t smell petrol in the exhaust fumes whereas before I could, early days but I’ll have a look at the plug colours later or tomorrow.
Good - hope it works - they are lovely when they run right. I must admit I wouldn't of thought of "reducing" the tower and gripping the jet directly. When I eventually finish my M900 project I have 2 sets of carbs that have been stuck in a box in case I can use any spares off them, they will now get that treatment
Good news it’s no longer running rich, I’ve no idea yet what was wrong with the original carb, I’ll have a closer look at it when I get time, I’ve been out on the monster all weekend and it’s now running great, very slightly lumpy tick over but I’ll balance the carbs next weekend (how the heck do you get to the balance screw!), thanks for you help and ideas above.
As I get older, it's far easier (if you can afford it) to swap carbs if they really are rogue. There comes a time when you need to wave the white flag unless it's a rare old Weber etc.
The only bonus of this issue is I’m now incredibly adept at removing airbox/electrics/carbs etc & then refitting, so if anyone needs a hand give me a shout, on second thoughts don’t , 6 times is enough for this lifetime
