I took off my carbs (NC30) to tweak the pilot screws after installing a carbon airbox.

The front right carb rubber was slightly chewed, so obviously I didn't get it perfect last time (about a year ago). At that time I installed all new rubbers.
Anyway, I got them back on, bike started up but didn't run well at all and had an obvious-sounding hissing air leak. Checked the carbs and I hadn't fully seated them. The best I can manage now is 'very nearly' seated, but the front right rubber is a little deformed and the ring-clamp won't grip it properly. Maybe I can take a photo, will try tomorrow.

So when I try to start the bike, I get an intermittent screeching kind of sound which doesn't sound metallic at all, but could hopefully be explained like somebody playing 'comb & tissue-paper' with rubber and ali if you get my meaning. I'm really hoping this is what the noise is, just air forcing past the edge of the rubber. Because if it isn't I will be a bit worried...

Has anyone else heard a noise like this? Was it an airleak? I should try to count how many cranks in between screeches to narrow it down...

Spray WD40 over the rubbers while the engines running, the engine will change speed if it's leaking air when it sucks in the wd

carb cleaner around the carb rubbers is a good way to check for leaks too

easier said than done on these bikes, but I tried it with inconclusive results, i.e. can't be sure I got it well enough to know.
I can't get it actually running at the moment.

I've just had the clutch fully apart and back together, is it possible I've somehow stuffed up the timing?
nah, couldn't be... It ran fine for a little while yesterday, with the hissing noise; only got worse once I 'fixed' that...

i had poorly seated carbs back in the summer after refitting the carbs and the bike ran like a pile of
but ran,started no probs.
i would be inclined to look and something else,double check over everything you done and make sure you have done it correctly,take the carbs off again and put them on taking your time and making sure they are seated correctly.just to rule that out!!!!!


william

Well I've replaced the carb rubber and it still makes this funny noise...

It occurred to me that maybe I didn't properly seal the clutch cover when re-installing it?
It was my first try at using 3-Bond and I wasn't quite prepared for the messiness so it took longer than I thought and maybe got too tacky and inconsistent...
Reckon the noise could be from air blowing through the clutch-cover joint? Might have to do that all over again...

Can anyone give me tips for working with 3-bond? There wasn't much available in the way of instructions, just "Apply as thinly and consistently as possible" so i might not have used enough? and once it started tacking up it wouldn't spread properly...

what about a clutch cover gasket



william

Is the bike actually running now?

You can pretty easily check that all carbs are seated properly, use a torch on the front carbs if you need to backs are easy to see.

I doubt it's due to a clutch cover leak (minor chance it could be though). Crankcase pump wouldn't be too noisy through a leak.