I'm pleased to report back on the 1st use on the road and its VERY good. Just got in, it was getting dark.
-easy 1st kick start as is usual now with VM28 carb 550 bodies / 380 top hybrid carbs, running only very briefly on LH before going cold and stinking of fuel in LH pipe (its getting TOO much fuel on choke in LH carb is my hunch! How, I’ve no idea for now). Off choke, usual 1100rpm smooth idle on 3 pots, so headed out, lights ablaze against the gloom. Roads mostly dry once out of the local lanes. Light winds, ~10C air temp.
-took it for a 22mile test ride. Immediate impressions are superb off-idle smoothness (tends to slightly rich but so little its not even worth dialing out), bags of power which seat of pants dyno suggests might be quite a bit more than on stock carbs, a sense that its no longer so picky about which gear its in, it pulls well from lower RPM and pulls higher gears uphill and into wind which it didn’t before, and finally, no hint at all of roll-off harshness or cruising on a cracked throttle jerkiness. A total pleasure to ride, perhaps better than ever in my 37 years of ownership. While they may be there for the taking, the main advantages may not be in top speed or willingness to rev (cannot really use the former as chassis gets fidgety about 85-90mph anyway, and I don’t like to flog my motors to the redline) but more in the creamy smoothness and a bit more urge all round. It will rev easily and freely to the redline in any gear (not yet tested 6th
) and no suggestion of wrong fueling off-idle, mid- or WOT.
-exhaust manifold temps were similar to before (or cooler, but was a cooler day than I usually ride) at around 100C LH and C, 95C on RH. Unless I find something worrying, I will keep these carbs in place for now. They have 550 jets inside (102.5 mains, 30 pilots, pilot screw 1.5 turns out).
So if anyone fancies a reversible 'hop up' for the 380, try this. While I'm over the moon, and probably over-reading the gains, I honestly think it might have added 10% to power, conservatively, and even that is noticeable. I have done nothing to airbox/air filters, reasoning that cannot be restrictive on this smaller engine, since its pretty much identical to the set up on the GT550B.
I had considered getting a spare head so I could try a 1mm skim but honestly, the change to 550 carbs is enough and I want to keep it as stock as possible. Also, it might embarrass its bigger brother, the 550B! no question my 750 is massively more powerful, even taking account of the greater weight, but with a stronger 380, my 550 will have its work cut out
) Roll on spring so I can run that contest of fun, which is all this is.
Cheers,
Mike
) the 380 is pretty soft and port timing suggests that it may not rev high enough to use that flow. An RZ350 makes around 60HP with two 26mm round slides. That tends to suggest that three 24's "ought" to be enough for a triple, but you just don't know until you try it.
