ORIGINAL: daggets
yes, you can modify the carburator of a so reputed brand such os, rossi, yamada... etc...
but, think...
they are able to design and build such a reputed mechanic and not able to make a tunable carburator?
in other word, you can also modify a car designed to burn premium gasoline, and make it run with regular....
but why?
os engine, like yamada are designed for us market, in this country, nitromethane is reasonably cheap, so it is used as an additve for glow fuel...
if you don t use this additive, you ll need a very high compression engine, but as soon as the compression weaken, the engine starts to be unstable...
thats why new engine are running strong on the beginning, and that after a short while, it s not the same anymore...
20 per cent nitro will solve that...
i m proud to talk with you, mister zeelon, it s constructive...
I've been re-profiling the low speed mixture needles on carbs, if they are of the twin needle style as a matter of course. The OEM has no idea how I'm going to use the engine and can't possibly design for the whole range of operating conditions. I often flew at 1800 meter altitude. It is very easy to re-profile the needle with a stone honing stick. This modification to the needle should be thought of as be no more complicated than finding the proper heat range of a glow plug and replacing the glow plug. This should be well within the scope of most engine enthusiasts to adjust (no special tools needed).
I find that if you should error on the low speed needle profile that the replacement needle is often less expensive than a glow plug.
Also some carb designs allow the fuel discharge port to be placed at different location in the venturi. This also allow for some tuning of the fuel mixture.
To my way of thinking these features, twin needle and adjustable spray bars (discharge ports), are tunable variable in the carbs you mention and account for their great reputation.
Now it is true that all manufacture can make a dud, such as the OS FX carb. I think I agree with you that nitro (20%)is a mask for a poor (design or worn out) engine as the cylinder fit and rod ends wear.
All the best,
Konrad
Edit for spelling