after months of Amal carb shenanigans...

[lingeringstin...]

I won't bore you with the pics but basically I'm running a two stroke Amal 375 carb on a sort-of Honda Rebel 250 clone type engine. Why? Nobody knows but that's what I'm doing.

After a plethora of teething troubles that could have been instantly sorted out by just using a four stroke jet tube thingy in the first place I'm currently running a 580 or 590 main jet (can't remember which now). That's a bit large since most old four stroke bikes of similar spec that ran these Monobloc carbs used main jets of between 100 to 200 at most, so me running nearly a 600 size jet is a bit weird but it works fine.

It's all down to the rocket science of how the slash cut two stroke jet tube differs from the straight across four stroke one. Other than that one little component there isn't any difference between a two stroke Monobloc and a four stroke one, and I've been running a two stroke one on a four stroke engine just to see if it could be done.

Adjustments are minimal. You can't even mess with the float height in the fuel bowl to any great degree. You've got the needle clip position, an air screw for the idle and a slide stop screw and that's it. There's some small jiggery pokery that can be done with slide cutaway and idle jet size but basically a Monobloc is a Monobloc is a Monobloc, and they're all bloody primitive. The tickler means there's no need for any kind of choke circuit, cables, knobs, levers or flappy gubbins and there isn't an air filter or airbox.

It's like something they came up with down the pub one evening in 1955 after spending all day designing a new bike. Like somebody had an "oh shit" moment and pointed out they'd forgotten to take a carb into consideration so Bob there just says ah don't worry about it I'll cobble up something tomorrow before the boss gets in and the Monobloc was the result.

I wouldn't dream of buying a new one for the price they ask but spares are plentiful for cobbling up secondhand ones. This carb is old and shit. However, it starts every time and gets good mileage. This has actually been the best carb I've ever had on this engine. Not the most performance, but the best as in it just never goes wrong or needs fiddling with, and that's sort of against my principles.