Arcing-type-sound

For the last few weeks my bike's been making an odd noise when starting from cold (and while the engine's cold, too). It fires up fine, first time, never fails, but after running for a few seconds there's a noise like an electrical arc (think gas-cooker spark ignition thingy type noise, but louder), the engine faulters and then carries on as normal.

It used to be that this was happening once every few weeks, so I thought nothing of it, just putting it down as a misfire. Recently, though, it's happening up to 5 times in the minute or so I leave it on choke, and will randomly do it for the first few minutes of riding. It doesn't seem to happen when the bike's above 3.5krpm, and seems to be worst when it's sat at approx. 2.5krmp (on the choke, or when maneuvring at low speed following starting the bike).

It's an 02 curvey, had fresh iridium spark plugs put in 3000 miles ago, had fairly regular services (and is booked in for one on Saturday where the mechanic's going to take a listen to it from cold), and the only mod is a slip-on.

Ideas?

[dizzyblonde]

check the HT leads for corrosion, and replace em, if that don't work, swap the coils. Would it be coming from under the seat somewhere??

sounds very familiar to me

It actually sounds like it's coming from the front cylinder-type area. Will do a thorough checkover later tonight or tomorrow

I reckon it's just the sound of your cams which can sound like the ticking of a gas cooker when your lighting it. It might explain why you can not really hear it after 3.5k revs because all the other noises drown it out.

Thats my 2 pennies anyway

[dizzyblonde]

Originally Posted by Neeja

It actually sounds like it's coming from the front cylinder-type area. Will do a thorough checkover later tonight or tomorrow

I thought the same til I shoved my ear next to the seat, plus YC and Im Indoors investigated it, they missed it the first time...worth a look. HT lead to the front cylinder??
Never heard of cams clicking like gas cookers though. Arcing makes me think of electrics. Check the loom round the headstock too, for any breaks or chaffs

Loom's fine, has been checked recently. Definitely not the cams 'cause it goes away when the engine is warm...plus they tick quite comfortingly under normal use and I'm used to it

Will have to check the HT lead when I get back