CB500 Engine Won't Start

[Ingah]

Tried to start my hellish (unreliable despite much TLC) CB500 up last week to get it warmed up to change the oil again, but it wouldn't stay alive - it turns over, catches even, but won't keep going when the starter button is released (dies immediately). Tried a few times, gave it a little rest in between, no go. Tried turning the fuel tap to reserve too. No difference.

Hadn't been used in a month and a half due to brake caliper troubles (brake calipers now nearly sorted - finally). Been kept in the garage, noteably was lots condensation ALL over the bike though.

Battery should be fine- been on trickle charge directly beforehand and even whilst turning the bike over. Have also got a spare battery so will check this 100%.
Kill switch off (won't turn over if it's not).
Spark plugs are 18 months old at most.
Air filter can't be more than 12-18 months old either.
Oil and filter is maybe 4 months old.

Intend to WD40 the safety/cut-off switches (side-stand, clutch, and killswitch come to mind) as i've had it being funny before due to the killswitch (solved by copious amounts of WD40) - i know it's not the same problem this time because with the killswitch pressed it won't even try to turn over, but that's not the point. However, time is of the essence - i want to get the problem fixed with as little extra time in the garage as possible as i'm really fed up of working on this unappreciative bike (if i'd wanted an unreliable bike, i wouldn't have bought a Honda CB500) - so with this in mind, any ideas?
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-- Ingah

[Glenben92]

I'd start by checking for BOTH sparks. Condensation could have gotten into the ignition circuit and blown a coil or cdi or both once it's had power run through it (i.e. when you first tried to start it again)
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57 Huoniao HN125-8 - , 97 Kawasaki GPZ500S -
99 Yamaha FZS 600 -
Mod 2 Passed - 01/10/2010

[stinkwheel]

Try draining the float bowls and catching the fuel that comes out in a jam jar to check for traces of water. If there is, run fresh fuel through and give the plugs a clean. Maybe stick a shot of meths in the tank to carry any remaining water through.

If there's loads of condensation on the outside, there could be similar inside the tank. You can sometimes even see it as a layer at the bottom of the tank if you shine a torch in there.

Also check fuel is actually coming out by detaching the fuel line and sucking on the vacuum line.

Or the ratbike way, hook it up to a car battery and give it a damned good cranking until it sees the error of its ways?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.