Ok, so two holes was stock on the classic Mikuni T3s. That then makes me wonder if it was the restricted rubbers affecting transient response (or really frequency response) which necessitated the reduced slide damping?
But surely that would mean that they would run worse when "unrestricted" rubbers were installed, and that's (from my experience) not the case.
But there is an issue remaining which definitely rings bells imo. Those 117.5 main jets. There is no way they should be appropriate without a very leaky airbox (or one drilled for at least double the intake area).
You could be right on the money there Mike because I just had a look on worldoftriumph, they only show the 3yclinder model airbox and it has two inlets, maybe the 4cyl is the same? That might account for the bigger mains.
So theoretically if I made a 2nd hole in my standard airbox, the Trophy carbs might run perfectly
....yeah I know but I can dream can't I?
But the main jet mainly matters at the top end only, with some lower interaction with the needle. Maybe what's been going on with those oversize mains is some serious suppression of needle travel by the Trophy (1 hole) slides to compensate. Go back to original slides & the great gob of fuel as the slide opens too fast completely bogs the motor.
This is where the backwards thinking bit comes into play - bogging occurs not from too much fuel, but from too much air! This is the part that I didn't understand either. As the slide opens wide, it does not
allow more fuel in - rather more air. Fuel can only be sucked out of the emulsion tubes if there is enough air velocity (speed), and as the slide rises the orifice gets bigger, creating lower air velocity and less fuel!!
The purpose of the slide is not to allow more air in, exactly the opposite, it's there to keep the opening as small as possible, in order to create the right velocity of air that can keep the supply of fuel going, and the air/fuel mix at the correct balance.
This is of course regulated also by the taper of the needle. It's all a matter of timing and I guess the needles are designed to start allowing more fuel to escape at a given slide height.
You've got an oxygen sensor permanently mounted haven't you? Try removing your airbox and see what it reads as the engine starts to bog, my bet is that it will read lean, not rich.
I once raised the DJ needles in mine by one notch (out of five) to see what happened. Didn't get more than 10 metres or 1st gear. Opening the throttle by even an 1/8 or so resulted in a momentary shove (good!) & then it bogged completely & would go no further. Not really possible to even get 2nd gear & hold it. (Fortunately needles are accessed without carb removal)
Yeah that sounds like a "too much fuel" bog down, because if everything else was setup as it should be, then that would allow more fuel out of the emulsion tubes for a given slide height.
In theory, at such low throttle (& revs) it should have made little difference - supposedly still on the straight part of the needle, not the taper. In practice however, it seems obvious from this that the transient response of slide (& needle) must be pretty important.
Yeah, the timing is critical.
ps have you read thru' the 'Hinkley faqs' collated from numerous T3 triple tuners? (they are around the forum somewhere I think)
I've only seen the "proven setups" thread, I like to do things the hard way lol.