Anyone tried putting 550 carbs on a 380?

[Vintageman]

wow 10 years ago. thanks for update markush.

first i wan to say gt550 carbs on a gt380 no way is it too much. it is lovely and you get direct increase in power in proprtion to added carb size. yup butt dyno. one way i knew for sure is when it gets up in rpm and horsepower, clutch would slip with this mod only. in my case stiffer clucth springs solved that pretty much. i was worried about running throttle position just off idle (cruising) that it would be rough, but not so. it is a really nice mod. an that should be a sticky reply for all that ask about it

i have changed port timing on 250, 305, 350 amd 380 in various ways over the years. of course the 250 has the early version then the 1976 and up with extra transfer ports and 29.5 mm exhaust height like rd350. that bike also from factory does not like to run below 4000 rpm. that engine is a rocket. put a set of DG chambers matched for aircooled rd350 and it really fast for old aircooled 250. almost dangerous as it can't be ridden slow (be me), it wants to simply go fast i took a 305 and raised ex port to about 30.5mm. it was even more peaky than the 250a. it would not run well below 4500 maybe 5000 and i had to change main jetting leaner else it would drown with fuel when trying to give it wot starting down low in rpms. once you were high in rpms, stock jetting was ofine, so going lean to streat ride made me nervous to run high rpms too long esle melt piston (never di though).
running 8000 rpm and up the cranks will not last long on these twins as i have leared a few times. the big end bearing are too small in my opinion. i am looking at using the pe175/ts185 rod, the big end eye is 2 mm wider, their are some silver cages bearing out there that has larger rollers to make up this difference so you can use same skinny stock crank pin. if you look at bearing spec only it seems it will give 10% increase in strength, And the early rod for 250, 305, 350 is obsolete. i am not sure if bigger rod will hit case, don't think so, but should know soon and make a separate post. it would be nice to find a step crank pin to replace stock one as write this post, but for now i think the may be a good mod, we'll see

my gt380 ex is raised about 0.5mm and widened about 2mm. jemco chanber will allow another +1000 rpm over rev/more power and went that route vs raising ex port higher. the gt380 is a very nice to streat ride, just little low in torque as it is little bike. it makes up for it once you get into higher rpms. it is avery nice bike for sure given what it is and reliable.