'80 CBX doesn't start suddendly

[loft1]

I took the bike last Tuesday, no problem at all, the bike runs fine. On Thursday, surprise! My CBX doesn't start anymore. I immediately think it's due to the battery, but the lights are on, so it seems there's power in the circuit. Anyway, yesterday i charged the battery completely, trying then again to crank the bike, but still the same issue. I believe there's something wrong with the spark plugs, perhaps a lean mixture has dirty them? Since i bought the CBX in July, i had no problem at all in cranking the bike (it's a bit slow, i will have soon an AGM battery). What could it be otherwise?
Here's a video of the issue, hope it can help you



https://youtu.be/mRAZHM_J5lY

[daves79x]

Most CBXs crank a lot longer than that to start after sitting. Apparently yours has not, until now. If the vacuum valve on your carbs is still in place, it may have failed. Not a common problem though. I'd try draining the carbs, then refilling with fresh gas. See what comes out of the bowls when you drain them.

Dave

[loft1]

Thanks Dave, i've found the cause, it was a contact in the kill engine switch, which wasn't working properly. Weird issue though

[daves79x]

Both left and right switches need to be completely disassembled and cleaned after 40 years. You'll be amazed at the crud and old hard grease in them.

Dave