When the bike is anywhere from cold, to just below 90 degrees (normal running temp, i hope?!) throttle response is very good, for a 400. However when I've got it warmed up and have got out of town I start to notice it feeling a bit sluggish. I'm pretty sure it's just as fast, and would have roughly the same power curve, but it just doesn't pick up right. It's more noticable at low throttle openings.

Sometimes, at a throttle opening that would have you accelerating when running well, the warm bike isn't pulling at all. Crack the throttle open and it'll go, it's not really a flatspot related to any particular part of the rev range, it's just poor response.

Any ideas at all? It's only a little problem, but it's doing my head in.

Thanks.

Theres a few mods you can do to stock NC30 carbs to get a better throttle respone.

The first is to enlarge the air pressure hole in the slider to 2.5mm to improve throttle response speed.

However, the symptoms your describing sound as tho it may be running too rich or lean at low rpm.

Ideally you could do with a bit of dyno time to analyse your fuel/air mixture before fettling with it, just in-case.

Reset the pilot screws to factory defaults first then to quote factorypro.

# If the engine has a "wet" rhythmic, soggy area at full throttle / 3k-4k rpm, that gets worse as the engine heats up, lower the fuel level by resetting the float height 1mm greater (if the original was 13mm - go to 14mm). This will lower the fuel level, making full throttle / 2k-3k rpm leaner.
# If the engine is "dry" and flat between 2k to 3k rpm, raise the fuel level.
# Example: change float height from 15mm to 14mm to richen up that area.

First thing really is to check everything is as honda intended, mainly valve clearances, float heights etc, then if it's still playing up start to mess.

Druid

make shure your choke slider on the carbs is returning to the off position , seen a few bikes with stiff cables and when you push the choke leaver into the off position the sticky cable holds the choke open on the carbs, so the choke is still on . runs good when cold and shite when hot . worth a look .