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Help! Iv got a 97 year cbr 918 that has developed a miss fire on cylinder 1 but it's doing some weird stuff, with the bike running and missing on cylinder one, if I pull the plug cap off the plug and just drop it in the head so it's close to the plug, the bike will pick up and start firing on all four but when I push the cap on properly it seems to Cut the cylinder out. I've checked the spark with a spare plug against the exhaust stud and it's got a nice blue spark, even when I start pulling the plug away from the stud it still gives a lovely spark until it gets about an inch away then it's too far, have put new plugs in and it was ok for about 2 weeks then started again. I have replaced the coils, plugs, rectifier and battery. also are the coils earthed through the frame or one of the wires going to the coil and what voltage should be going to the coils as it does not say in the manual
 

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If possible can you swap over #1 and #4 HT leads over and see if you get a fault on #4 cylinder (no need to take the leads off the coil , just swap them over)
IDK
 

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If possible can you swap over #1 and #4 HT leads over and see if you get a fault on #4 cylinder (no need to take the leads off the coil , just swap them over)
IDK
It's a phenomenon that used to be used back in the old days to get the last out of a failing coil - install a spark gap. don't know precisely how it works but the bottom line is that the coil for that cylinder is on its way out. Oh wait - you've replaced everything. then it's as you say, something is not earthing properly.
 

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It sounds like wiring or coil issue. If you're confident that your compression on cylinder 1 is fine and it's delivering fuel properly then try switching coils to see if the miss fire moves.

I've had many ignition coils fail on me and they either fail on the spot or gradually until the ECU gets triggered and limp mode occurs. Maybe, you have a worn out spark plug. How is the insulator on the wires any cuts or worn areas where a spark could jump?
 
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